E Grand Rounds Presentation Pachyonychia Congenita€¦ · E Grand Rounds Presentation Pachyonychia...

S A M P L E

Grand Rounds Presentation

Pachyonychia Congenita

presented by

[Name, Credentials, Affiliation]

sponsored by PC Project

Table of Contents

Welcome—PC Project, IPCRR, IPCC ....................................................... 2

IPCRR Status Data / Invitation to join the IPCC

Chart of Mutations / Schematic of Mutations .......................................3

IPCRR Data Summary (712 genetically confirmed with PC) ................... 4

Presentation of Patients for Grand Rounds

PC-K6a

IPCRR #72 K6a L468P .......................................................................5

IPCRR #344 K6a L469P .......................................................................6

IPCRR #820 K6a L469R ........................................................................7

IPCRR #1338 K6a N172del .....................................................................8

PC-K6b

IPCRR #641 K6b E472K .......................................................................9

PC-K6c

IPCRR #713 K6c E472K .................................................................... 10

PC-K16

IPCRR #35 K16 R127P ..................................................................... 11

IPCRR #66 K16 L132P .................................................................... 12

IPCRR #850 K16 R418P .................................................................... 13

IPCRR #1578 K16 M121T .................................................................... 14

PC-K17

IPCRR #515 K17 N92S ....................................................................... 15

List of Selected Articles .............................................................................. 16

Full text articles ..................................................................................................

Sep 2016

Welcome!

Pachyonychia Congenita Project (PC Project) is a public charity in the USA which

sponsors the International Pachyonychia Congenita Research Registry (IPCRR)

serving patients around the world. Beginning with 3 patients in 2004, the IRB-

approved registry has now enrolled over 1700 individuals diagnosed with PC. Of

these, 968 have complete data on file in the IPCRR including patient input-

physician validated data, images and genetic testing results and of those 727 have

confirmed PC.

Pachyonychia Congenita Project (PC Project) also sponsors the International Pach-

yonychia Consortium (IPCC) a collaboration of physicians and scientists working

in clinical care as well as basic and translational research to improve lives for those

with PC and tofind effective treatments. If you’d like to join this open membership

group and receive the quarterly newsletters, please include your name and contact

details in an email request to [email protected].

2

Location of genetically confirmed individuals with PC

4

PC-K6a

N=276

PC-K6b

N=67

PC-K6c

N=22

PC-K16

N=231

PC-K17

N=116

All PC Genes

N=712

273 of 276 (99%) 66 of 67 (99%) 13 of 22 (59%) 223 of 231 (97%) 112 of 116 (97%) 687 of 712 (96%)

259 of 276 (94%) 24 of 67 (36%) 0 of 22 (00%) 94 of 231 (41%) 87 of 116 (75%) 464 of 712 (65%)

8 of 276 (03%) 14 of 67 (21%) 0 of 22 (00%) 29 of 231 (13%) 10 of 116 (09%) 61 of 712 (09%)

2 of 276 (01%) 19 of 67 (28%) 3 of 22 (14%) 59 of 231 (26%) 7 of 116 (06%) 90 of 712 (13%)

4 of 276 (01%) 9 of 67 (13%) 10 of 22 (45%) 41 of 231 (18%) 8 of 116 (07%) 72 of 712 (10%)

Toenails - Onset N = 273 N = 66 N = 13 N = 223 N = 112 N = 696

Birth or less than 1 year 239 of 273 (88%) 9 of 66 (14%) 1 of 13 (08%) 44 of 223 (20%) 79 of 112 (71%) 372 of 696 (53%)

1 to 4 years old 30 of 273 (11%) 16 of 66 (24%) 6 of 13 (46%) 72 of 223 (32%) 24 of 112 (21%) 148 of 696 (21%)


15 years and over 0 of 273 (00%) 7 of 66 (11%) 2 of 13 (15%) 38 of 223 (17%) 1 of 112 (01%) 48 of 696 (07%)

273 of 276 (99%) 31 of 67 (46%) 0 of 22 (00%) 136 of 231 (59%) 98 of 116 (84%) 538 of 712 (76%)

244 of 276 (88%) 4 of 67 (06%) 0 of 22 (00%) 71 of 231 (31%) 50 of 116 (43%) 369 of 712 (52%)

9 of 276 (03%) 4 of 67 (06%) 0 of 22 (00%) 11 of 231 (05%) 12 of 116 (10%) 36 of 712 (05%)

14 of 276 (05%) 16 of 67 (24%) 0 of 22 (00%) 28 of 231 (12%) 27 of 116 (23%) 85 of 712 (12%)

6 of 276 (02%) 7 of 67 (10%) 0 of 22 (00%) 26 of 231 (11%) 9 of 116 (08%) 48 of 712 (07%)

Fingernails - Onset N = 273 N = 31 N = 0 N = 136 N = 98 N = 538





243 of 276 (88%) 64 of 67 (96%) 19 of 22 (86%) 227 of 231 (98%) 91 of 116 (78%) 644 of 712 (90%)

233 of 276 (84%) 63 of 67 (94%) 19 of 22 (86%) 226 of 231 (98%) 74 of 116 (64%) 615 of 712 (86%)

5 of 276 (02%) 1 of 67 (01%) 0 of 22 (00%) 1 of 231 (00%) 13 of 116 (11%) 20 of 712 (03%)

6 of 276 (02%) 0 of 67 (00%) 0 of 22 (00%) 0 of 231 (00%) 4 of 116 (03%) 10 of 712 (01%)

Plantar Keratoderma- Onset N = 243 N = 64 N = 19 N = 227 N = 91 N = 644





236 of 243 (97%) 64 of 64 (100%) 19 of 19 (100%) 217 of 227 (96%) 77 of 91 (85%) 613 of 644 (95%)

61 of 243 (25%) 11 of 64 (17%) 5 of 19 (26%) 70 of 227 (31%) 17 of 91 (19%) 164 of 644 (25%)

105 of 243 (43%) 32 of 64 (50%) 11 of 19 (58%) 103 of 227 (45%) 28 of 91 (31%) 279 of 644 (43%)

70 of 243 (29%) 21 of 64 (33%) 3 of 19 (16%) 47 of 227 (21%) 32 of 91 (35%) 173 of 644 (27%)

152 of 276 (55%) 28 of 67 (42%) 6 of 22 (27%) 173 of 231 (75%) 60 of 116 (52%) 419 of 712 (59%)

81 of 276 (29%) 11 of 67 (16%) 2 of 22 (09%) 139 of 231 (60%) 16 of 116 (14%) 249 of 712 (35%)

26 of 276 (09%) 6 of 67 (09%) 1 of 22 (05%) 14 of 231 (06%) 19 of 116 (16%) 66 of 712 (09%)

45 of 276 (16%) 11 of 67 (16%) 3 of 22 (14%) 20 of 231 (09%) 24 of 116 (21%) 103 of 712 (14%)

247 of 276 (89%) 18 of 67 (27%) 4 of 22 (18%) 83 of 231 (36%) 29 of 116 (25%) 381 of 712 (54%)

178 of 276 (64%) 47 of 67 (70%) 4 of 22 (18%) 59 of 231 (26%) 107 of 116 (92%) 395 of 712 (55%)

155 of 276 (56%) 29 of 67 (43%) 0 of 22 (00%) 28 of 231 (12%) 75 of 116 (65%) 287 of 712 (40%)

8 of 276 (03%) 0 of 67 (00%) 0 of 22 (00%) 0 of 231 (00%) 88 of 116 (76%) 96 of 712 (13%)

1-3 fingernails thickened

Plantar Keratoderma

Always (never goes away)

Seldom (hands usually clear)

Other

Sometimes (clear up at times)

Seldom (feet usually clear)

Plantar Pain

Often require meds for pain

1-3 toenails thickened

Fingernail Dystrophy

all 10 fingernails thickened



IPCRR Data 7 Jul 2016

Toenails Dystrophy

all 10 toenails thickened



Oral Leukokeratosis

Cysts

Follicular Hyperkeratosis

Very painful, but do not use meds

Somewhat painful

Palmar Keratoderma



Natal or Prenatal Teeth

International Pachyonychia Congenita Research Registry (IPCRR)

Questionnaire Summary Data as of July 2016

5

PC-K6a

N=276

273 of 276 (99%)

259 of 276 (94%)

8 of 276 (03%)

2 of 276 (01%)

4 of 276 (01%)

Toenails - Onset N = 273

Birth or less than 1 year 239 of 273 (88%)

1 to 4 years old 30 of 273 (11%)

5 to 14 years old 4 of 273 (01%)

15 years and over 0 of 273 (00%)

273 of 276 (99%)

244 of 276 (88%)

9 of 276 (03%)

14 of 276 (05%)

6 of 276 (02%)

Fingernails - Onset N = 273


1 to 4 years old 27 of 273 (10%)

5 to 14 years old 3 of 273 (01%)


243 of 276 (88%)

233 of 276 (84%)

5 of 276 (02%)

6 of 276 (02%)

Plantar Keratoderma- Onset N = 243


1 to 4 years old 143 of 243 (59%)

5 to 14 years old 62 of 243 (26%)


236 of 243 (97%)

61 of 243 (25%)

105 of 243 (43%)

70 of 243 (29%)

152 of 276 (55%)

81 of 276 (29%)

26 of 276 (09%)

45 of 276 (16%)

247 of 276 (89%)

178 of 276 (64%)

155 of 276 (56%)

8 of 276 (03%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K6a L468PData for IPCRR #72

Toenails Dystrophy





6

PC-K6a

N=276

273 of 276 (99%)

259 of 276 (94%)

8 of 276 (03%)

2 of 276 (01%)

4 of 276 (01%)



1 to 4 years old 30 of 273 (11%)

5 to 14 years old 4 of 273 (01%)


273 of 276 (99%)

244 of 276 (88%)

9 of 276 (03%)

14 of 276 (05%)

6 of 276 (02%)



1 to 4 years old 27 of 273 (10%)

5 to 14 years old 3 of 273 (01%)


243 of 276 (88%)

233 of 276 (84%)

5 of 276 (02%)

6 of 276 (02%)



1 to 4 years old 143 of 243 (59%)

5 to 14 years old 62 of 243 (26%)


236 of 243 (97%)

61 of 243 (25%)

105 of 243 (43%)

70 of 243 (29%)

152 of 276 (55%)

81 of 276 (29%)

26 of 276 (09%)

45 of 276 (16%)

247 of 276 (89%)

178 of 276 (64%)

155 of 276 (56%)

8 of 276 (03%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K6a L469P Data for IPCRR #344

Toenails Dystrophy





7

PC-K6a

N=276

273 of 276 (99%)

259 of 276 (94%)

8 of 276 (03%)

2 of 276 (01%)

4 of 276 (01%)



1 to 4 years old 30 of 273 (11%)

5 to 14 years old 4 of 273 (01%)


273 of 276 (99%)

244 of 276 (88%)

9 of 276 (03%)

14 of 276 (05%)

6 of 276 (02%)



1 to 4 years old 27 of 273 (10%)

5 to 14 years old 3 of 273 (01%)


243 of 276 (88%)

233 of 276 (84%)

5 of 276 (02%)

6 of 276 (02%)



1 to 4 years old 143 of 243 (59%)

5 to 14 years old 62 of 243 (26%)


236 of 243 (97%)

61 of 243 (25%)

105 of 243 (43%)

70 of 243 (29%)

152 of 276 (55%)

81 of 276 (29%)

26 of 276 (09%)

45 of 276 (16%)

247 of 276 (89%)

178 of 276 (64%)

155 of 276 (56%)

8 of 276 (03%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K6a L469RData for IPCRR #820

Toenails Dystrophy





8

PC-K6a

N=276

273 of 276 (99%)

259 of 276 (94%)

8 of 276 (03%)

2 of 276 (01%)

4 of 276 (01%)



1 to 4 years old 30 of 273 (11%)

5 to 14 years old 4 of 273 (01%)


273 of 276 (99%)

244 of 276 (88%)

9 of 276 (03%)

14 of 276 (05%)

6 of 276 (02%)



1 to 4 years old 27 of 273 (10%)

5 to 14 years old 3 of 273 (01%)


243 of 276 (88%)

233 of 276 (84%)

5 of 276 (02%)

6 of 276 (02%)



1 to 4 years old 143 of 243 (59%)

5 to 14 years old 62 of 243 (26%)


236 of 243 (97%)

61 of 243 (25%)

105 of 243 (43%)

70 of 243 (29%)

152 of 276 (55%)

81 of 276 (29%)

26 of 276 (09%)

45 of 276 (16%)

247 of 276 (89%)

178 of 276 (64%)

155 of 276 (56%)

8 of 276 (03%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K6a N172delData for IPCRR #1338

Toenails Dystrophy





9

PC-K6b

N=67

66 of 67 (99%)

24 of 67 (36%)

14 of 67 (21%)

19 of 67 (28%)

9 of 67 (13%)



1 to 4 years old 16 of 66 (24%)

5 to 14 years old 34 of 66 (52%)


31 of 67 (46%)

4 of 67 (06%)

4 of 67 (06%)

16 of 67 (24%)

7 of 67 (10%)



1 to 4 years old 7 of 31 (23%)

5 to 14 years old 11 of 31 (35%)


64 of 67 (96%)

63 of 67 (94%)

1 of 67 (01%)

0 of 67 (00%)



1 to 4 years old 20 of 64 (31%)

5 to 14 years old 41 of 64 (64%)


64 of 64 (100%)

11 of 64 (17%)

32 of 64 (50%)

21 of 64 (33%)

28 of 67 (42%)

11 of 67 (16%)

6 of 67 (09%)

11 of 67 (16%)

18 of 67 (27%)

47 of 67 (70%)

29 of 67 (43%)

0 of 67 (00%)

Oral Leukokeratosis

Cysts



Other




Plantar Pain



Somewhat painful

Palmar Keratoderma




Plantar Keratoderma

K6b E472KData for IPCRR #641

Toenails Dystrophy










10

PC-K6c

N=22

13 of 22 (59%)

0 of 22 (00%)

0 of 22 (00%)

3 of 22 (14%)

10 of 22 (45%)




5 to 14 years old 4 of 13 (31%)


0 of 22 (00%)

0 of 22 (00%)

0 of 22 (00%)

0 of 22 (00%)

0 of 22 (00%)






19 of 22 (86%)

19 of 22 (86%)

0 of 22 (00%)

0 of 22 (00%)




5 to 14 years old 9 of 19 (47%)


19 of 19 (100%)

5 of 19 (26%)

11 of 19 (58%)

3 of 19 (16%)

6 of 22 (27%)

2 of 22 (09%)

1 of 22 (05%)

3 of 22 (14%)

4 of 22 (18%)

4 of 22 (18%)

0 of 22 (00%)

0 of 22 (00%)

Plantar Keratoderma

K6c E472K Data for IPCRR #713

Toenails Dystrophy










Other




Plantar Pain



Somewhat painful

Palmar Keratoderma




Oral Leukokeratosis

Cysts



11

PC-K16

N=231

223 of 231 (97%)

94 of 231 (41%)

29 of 231 (13%)

59 of 231 (26%)

41 of 231 (18%)



1 to 4 years old 72 of 223 (32%)

5 to 14 years old 68 of 223 (30%)


136 of 231 (59%)

71 of 231 (31%)

11 of 231 (05%)

28 of 231 (12%)

26 of 231 (11%)



1 to 4 years old 40 of 136 (29%)

5 to 14 years old 33 of 136 (24%)


227 of 231 (98%)

226 of 231 (98%)

1 of 231 (00%)

0 of 231 (00%)



1 to 4 years old 124 of 227 (55%)

5 to 14 years old 77 of 227 (34%)


217 of 227 (96%)

70 of 227 (31%)

103 of 227 (45%)

47 of 227 (21%)

173 of 231 (75%)

139 of 231 (60%)

14 of 231 (06%)

20 of 231 (09%)

83 of 231 (36%)

59 of 231 (26%)

28 of 231 (12%)

0 of 231 (00%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K16 R127PData for IPCRR #35

Toenails Dystrophy





12

PC-K16

N=231

223 of 231 (97%)

94 of 231 (41%)

29 of 231 (13%)

59 of 231 (26%)

41 of 231 (18%)



1 to 4 years old 72 of 223 (32%)

5 to 14 years old 68 of 223 (30%)


136 of 231 (59%)

71 of 231 (31%)

11 of 231 (05%)

28 of 231 (12%)

26 of 231 (11%)



1 to 4 years old 40 of 136 (29%)

5 to 14 years old 33 of 136 (24%)


227 of 231 (98%)

226 of 231 (98%)

1 of 231 (00%)

0 of 231 (00%)



1 to 4 years old 124 of 227 (55%)

5 to 14 years old 77 of 227 (34%)


217 of 227 (96%)

70 of 227 (31%)

103 of 227 (45%)

47 of 227 (21%)

173 of 231 (75%)

139 of 231 (60%)

14 of 231 (06%)

20 of 231 (09%)

83 of 231 (36%)

59 of 231 (26%)

28 of 231 (12%)

0 of 231 (00%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K16 L132PData for IPCRR #66

Toenails Dystrophy





13

PC-K16

N=231

223 of 231 (97%)

94 of 231 (41%)

29 of 231 (13%)

59 of 231 (26%)

41 of 231 (18%)



1 to 4 years old 72 of 223 (32%)

5 to 14 years old 68 of 223 (30%)


136 of 231 (59%)

71 of 231 (31%)

11 of 231 (05%)

28 of 231 (12%)

26 of 231 (11%)



1 to 4 years old 40 of 136 (29%)

5 to 14 years old 33 of 136 (24%)


227 of 231 (98%)

226 of 231 (98%)

1 of 231 (00%)

0 of 231 (00%)



1 to 4 years old 124 of 227 (55%)

5 to 14 years old 77 of 227 (34%)


217 of 227 (96%)

70 of 227 (31%)

103 of 227 (45%)

47 of 227 (21%)

173 of 231 (75%)

139 of 231 (60%)

14 of 231 (06%)

20 of 231 (09%)

83 of 231 (36%)

59 of 231 (26%)

28 of 231 (12%)

0 of 231 (00%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K16 R418PData for IPCRR #850

Toenails Dystrophy





14

PC-K16

N=231

223 of 231 (97%)

94 of 231 (41%)

29 of 231 (13%)

59 of 231 (26%)

41 of 231 (18%)



1 to 4 years old 72 of 223 (32%)

5 to 14 years old 68 of 223 (30%)


136 of 231 (59%)

71 of 231 (31%)

11 of 231 (05%)

28 of 231 (12%)

26 of 231 (11%)



1 to 4 years old 40 of 136 (29%)

5 to 14 years old 33 of 136 (24%)


227 of 231 (98%)

226 of 231 (98%)

1 of 231 (00%)

0 of 231 (00%)



1 to 4 years old 124 of 227 (55%)

5 to 14 years old 77 of 227 (34%)


217 of 227 (96%)

70 of 227 (31%)

103 of 227 (45%)

47 of 227 (21%)

173 of 231 (75%)

139 of 231 (60%)

14 of 231 (06%)

20 of 231 (09%)

83 of 231 (36%)

59 of 231 (26%)

28 of 231 (12%)

0 of 231 (00%)

Oral Leukokeratosis

Cysts



Somewhat painful

Palmar Keratoderma




Other




Plantar Pain








Plantar Keratoderma

K16 M121TData for IPCRR #1578

Toenails Dystrophy





Selected Articles

Key articles selected from over 700 full text articles with English translations regarding PC

and related research and disorders available on the PC Project website www.pachyonychia.org.

Eliason MJ, Leachman SA, Feng BJ, Schwartz ME, Hansen CD. A review of the clinical

phenotype of 254 patients with genetically confirmed pachyonychia congenita. Journal

of the American Academy of Dermatology. Oct 2012;67(4):680-686.

Goldberg I, Fruchter D, Meilick A, Schwartz ME, Sprecher E. Best treatment practices for

pachyonychia congenita. Journal of the European Academy of Dermatology and Venere-

ology : JEADV. Jan 30 2013.

Gonzalez-Ramos J, Sendagorta-Cudos E, Gonzalez-Lopez G, Mayor-Ibarguren A, Feltes-

Ochoa R, Herranz-Pinto P. Efficacy of botulinum toxin in pachyonychia congenita type

1: report of two new cases. Dermatologic therapy. Oct 7 2015.

Gruber R, Edlinger M, Kaspar RL, et al. An appraisal of oral retinoids in the treatment of

pachyonychia congenita. Journal of the American Academy of Dermatology. Jun 2012;66

(6):e193-199.

Leachman SA, Hickerson RP, Schwartz ME, Bullough EE, Hutcherson SL, Boucher KM,

Hansen CD. Eliason, MJ, Srivatsa GS, Kornbrust DJ, Smith FJ McLean, WH, Milstone

LM, Kaspar RL.First-in-human Mutation-targeted siRNA Phase 1b Trial of an Inher-

ited Skin Disorder. Mol Ther 2009 Nov 24.

McGrath JA. Pachyonychia congenita: cast in translation. The Journal of investigative der-

matology. May 2011;131(5):995.

McLean WH, Hansen CD, Eliason MJ, Smith FJ. The phenotypic and molecular genetic

features of pachyonychia congenita. The Journal of investigative dermatology. May

2011;131(5):1015-1017.

Schwartz ME, Zimmerman GM, Smith FJ, Sprecher E. Pachyonychia Congenita Project: A

Partnership of Patient and Medical Professional. J Derm Nurses Association. January/

February 2013;5(1):42-47.

Schwartz MD, Hansen CD, Paller A, Smith FJD, Sprecher E. Pachyonychia Congenita

Overview. The Dermatologist. 2014:22(4); 26-38.

Shah S, Boen M, Kenner-Bell B, Schwartz M, Rademaker A, Paller AS. Pachyonychia

Congenita in Pediatric Patients: Natural History, Features, and Impact. JAMA derma-

tology. Oct 16 2013.

Wallis T, Poole CD, Hoggart B. Can skin disease cause neuropathic pain? A study in

pachyonychia congenita. Clinical and Experimental Dermatology. Sep 11 2015.

Wilson NJ, Leachman SA, Hansen CD, et al. A large mutational study in pachyonychia

congenita. The Journal of investigative dermatology. May 2011;131(5):1018-1024.

Wilson NJ, O'Toole EA, Milstone LM, Hansen CD, Shepherd AA, Ali-Ashadi E, Schwartz

ME, McLean WHI, Sprecher E, Smith JFD. The molecular genetic analysis of the

expanding pachyonychia congenita case collection. The British Journal of Dermatology.

Aug 2014;171(2):343-355.

14

ORIGINAL ARTICLE

A review of the clinical phenotype of 254 patients withgenetically confirmed pachyonychia congenita

Mark J. Eliason, MD,a Sancy A. Leachman, MD, PhD,a Bing-jian Feng, PhD,a Mary E. Schwartz, AA,b

and C. David Hansen, MDa

Salt Lake City, Utah

Background: Pachyonychia congenita (PC) is a group of autosomal dominant keratinizing disorderscaused by a mutation in one of 4 keratin genes. Previous classification schemes have relied on data fromcase series and case reports. Most patients in these reports were not genetically tested for PC.

Objective: We sought to clarify the prevalence of clinical features associated with PC.

Methods: We surveyed 254 individuals with confirmed keratin mutations regarding their experience withclinical findings associated with PC. Statistical comparison of the groups by keratin mutation wasperformed using logistic regression analysis.

Results: Although the onset of clinical symptoms varied considerably among our patients, a diagnostictriad of toenail thickening, plantar keratoderma, and plantar pain was reported by 97% of patients with PCby age 10 years. Plantar pain had the most profound impact on quality of life. Other clinical findingsreported by our patients included fingernail dystrophy, oral leukokeratosis, palmar keratoderma, follicularhyperkeratosis, hyperhidrosis, cysts, hoarseness, and natal teeth. We observed a higher likelihood of oralleukokeratosis in individuals harboring KRT6A mutations, and a strong association of natal teeth and cystsin carriers of a KRT17 mutation. Most keratin subgroups expressed a mixed constellation of findingshistorically reported as PC-1 and PC-2.

Limitations: Data were obtained through questionnaires, not by direct examination. Patients were self- orphysician-referred.

Conclusions: We propose a new classification for PC based on the specific keratin gene affected to helpclinicians improve their diagnostic and prognostic accuracy, correct spurious associations, and improvetherapeutic development. ( J Am Acad Dermatol 10.1016/j.jaad.2011.12.009.)

Key words: genodermatosis; hyperkeratosis; keratin; keratinizing disorder; keratoderma; pachyonychiacongenita.

Pachyonychia congenita (PC) is a group ofautosomal dominant disorders caused by amutation in one of 4 keratin genes: KRT6A,

KRT6B, KRT16, or KRT17.1-5 There are an estimated5000 to 10,000 cases worldwide.6 The variable clin-ical findings affect a number of ectodermal struc-tures, including nails, skin, teeth, and oral mucosa.2

Although Muller7 and Wilson and Cantar8 arecredited with describing PC in 1904, Jadassohn and

Lewandowski,9 whose names constitute the eponymfor PC type 1, published the first case series of twosiblings in 1906. Kumer and Loos10 proposed a

From the Department of Dermatology, University of Utaha; and

Pachyonychia Congenita Project.b

Funded by the Pachyonychia Congenita Project.

Conflicts of interest: None declared.

Accepted for publication December 8, 2011.

Reprint requests: C. David Hansen, MD, Department of

Dermatology, University of Utah, 4A330 School of

Medicine, Salt Lake City, UT 84132. E-mail: david.hansen@

hsc.utah.edu.

Published online January 19, 2012.

0190-9622/$36.00

� 2011 by the American Academy of Dermatology, Inc.

doi:10.1016/j.jaad.2011.12.009

Abbreviations used:

IPCRR: International Pachyonychia CongenitaResearch Registry

OR: odds ratioPC: pachyonychia congenita

1

clinical classification scheme for PC variants based ontheir report of a 5-generation family with 23 affectedfamily members. Classification criteria were devel-oped and refined over subsequent years by authorswho painstakingly reviewed and summarized theavailable literature.11-19 Two clinical subtypesultimately emerged, the Jadassohn-LewandowskiPC type 1 and the Jackson-Lawler PC type 2.

In 1994, Munro et al20

studied a large Jackson-Lawler pedigree and linkedthe first PC gene to chromo-some 17q12-q21. In 1995,McLean et al3 identified thefirst causative mutations inkeratin genes KRT16 andKRT17. Additional mutationswere subsequently identifiedin KRT6a and KRT6begenesencoding the type II keratinsthat form heteropolymerswith type I keratins K16and K17.4,5 The identification of these mutationsand the advent of clinical genetic testing allowed theclassification of PC based on clinical and geneticcriteria.

Erroneous reports of PCmanifestations in patientswho did not have PC have been clarified by inves-tigators through genetic testing.21 Large, well-characterized and mutation-confirmed pedigreesoffer the opportunity to draw valid conclusionsregarding genotype-phenotype relationships.22

However, even these pedigrees are prone to biasbecause of shared modifier genes and environmentsthat might influence the clinical presentation. Thisreport summarizes data collected from 254 patientswith mutation-verified PC (derived from 147 fami-lies) and, to our knowledge, represents the largestand most comprehensive genotype-phenotypestudy of PC to date.

METHODSIn 2004, the International Pachyonychia

Congenita Research Registry (IPCRR) was estab-lished by the nonprofit organization PachyonychiaCongenita Project to collect clinical and geneticdata on patients with PC worldwide. The registrywas approved by the Western Institutional ReviewBoard (study #20040468). All patients gave writteninformed consent and the study was conductedaccording to the Declaration of HelsinkiPrinciples. Participant enrollment began in May2004.

Participants in the registry were solicited throughan Internet WorldWideWeb site designed to educatepatients and physicians about PC (www.pachyonychia.org). Referral to the registry was per-mitted through patients, family, physicians, andfamily expansion. To be included in the registry,each patient completed a detailed questionnaire

and provided information re-garding whether and to whatextent they were affected bythe clinical features of PC.Patients were also askedabout the age of onset andthe impact each feature hadon their quality of life. Thecompleted questionnaire,along with photographs ofvisible skin and nail changes,was submitted to the IPCRR.A telephone consultationwasthen arranged with a derma-tologist on the PachyonychiaCongenita Project medical

advisory board to: (1) clarify any confusingor missing information from the questionnaire;(2) confirm that the clinical features were consistentwith PC; and (3) provide genetic counseling beforemutation testing. Genetic testing was providedwithout charge and was performed in Dr FrancesSmith’s laboratory, University of Dundee, College ofLife Sciences, Division of Molecular Medicine,Dundee, Scotland. Before being released to pa-tients, the results were confirmed by independenttesting of a buccal DNA sample by GeneDx(Gaithersburg, Maryland), a US Clinical LaboratoryImprovement Amendmentsecertified laboratory.All participant data included in the analysis werefrom patients with a confirmed PC keratin mutation.

Statistical methodsWe performed logistic regression analysis to com-

pare how different PC keratin mutations influencethe probability of developing a specific clinicalfinding. For outcomes such as age of onset andquality of life, ordinal logistic regression was used.Because there were more KRT6A carriers than othermutation carriers we used the frequency of a trait inthe KRT6A group as a reference when calculatingodds ratios (OR) for the same trait to occur in theother keratin groups. To increase the power ofanalysis, all family members having a PC phenotypewere included in the test, with intrafamilial correla-tion adjusted. Software was used to perform thecomparisons (STATA v9.2, StataCorp, CollegeStation, TX).

CAPSULE SUMMARY

d Pachyonychia congenita (PC), a raregenodermatosis caused by mutations inkeratin genes, is currently classified asPC-1 and PC-2 based on clinical features.

d We report the prevalence of clinicalfindings in 254 patients with geneticallyconfirmed PC.

d We propose a new classification systembased on the specific keratin mutation(eg, PC-6a, PC-6b, PC-16, PC-17).

J AM ACAD DERMATOL2 Eliason et al

RESULTSAn international case series of patients withmutation-verified PC

At the time the data were collected, 254 individ-uals had completed the necessary steps for inclusionin the IPCRR (Table I). Additional demographics (eg,country of residence) can be found at www.pachyonychia.org. In addition to the 254 patientsharboring keratin mutations in one of the 4 ‘‘classic’’PC genes (KRT6A, KRT6B, KRT16, and KRT17) 34other individuals were found to have no detectablemutation, or mutations in other genes includingconnexin-30, KRT6C,23 and desmoglein-1. In thisarticle we will focus on the results of those withmutations in the 4 classic PC keratin genes.

We present the most commonly reported clinicalfindings according to mutation status in Table II.

Major phenotypic features of PCThree clinical features that were reported in more

than 90% of patients across all mutation subtypeswere thickened toenails, plantar keratoderma, andplantar pain (Table II).

Thickened toenails. Thickened toenails (Fig 1)were the most frequently reported clinical finding inthe IPCRR with 249 of 254 (98%) patients reportingthis phenotype (Table II). The average number oftoenails affected was 8.8 (range 0-10, mode = 10). Weperformed logistic regression analysis to comparethe relative likelihood of having all 10 toenailsaffected between the different PC keratin mutationcarriers. Using the prevalence of 10 affected nails inparticipants with mutations in KRT6B, KRT16, andKRT17 as the reference, we found that KRT6Amutation carriers were 11.1 times as likely (P \.001) to have all 10 toenails affected. The average ageof onset of toenail dystrophy across all keratinmutation types was 2.8 years with a median of 0.08years (1 month). KRT6A mutation carriers had theearliest average onset at 0.35 years (about 4 months).The average age of onset for patients with a KRT6B,KRT16, and KRT17 mutations was 9.5, 6.8, and 0.9years, respectively.

Plantar keratoderma. Plantar keratoderma(Fig 2) was the next most commonly reportedfinding, present in 241 of 254 (95%) patients (TableII). The registry includes individuals of ages youngerthan 1 year to older than 86 years (Table I). Of the 13individuals who were not reported as having plantarkeratoderma, 9 were younger than 1 year, and theoldest was 3 years of age (data not shown). Plantarkeratoderma can variably manifest as calluses, blis-tering, fissures, thickened skin, and open sores. Mostpatients experienced more than one of these

manifestations of keratoderma, with calluses beingthe most commonly reported (210/223, 94%) (datanot shown).

To better understand the persistence of the plan-tar lesions, patients were asked to approximate howlong the lesions lasted: 228 of 254 (95%) indicatedthat their feet were always affected and that thelesions never completely resolved. Among 241 pa-tients who reported the age of onset of their plantarkeratoderma, the average age was 4.2 years with arange of 0 (birth) to 30 years, and amedian andmodeof 3 and 2 years, respectively. Of patients, 20% wereaffected by 1 year of age and 66% were affected by 4years of age (data not shown).

We found that the KRT16mutation carriers devel-oped plantar keratoderma at a similar age to KRT6Acarriers whereas KRT6B and KRT17 carriers weresignificantly more likely to report later onset.

Plantar pain. Plantar pain was reported by 225of 254 (89%) surveyed patients. The prevalence ofpain was high across keratin subgroups (Table II).The age of the patient was found to have a dramaticeffect on the reporting of plantar pain: only 3 patientsolder than 10 years did not report plantar pain (datanot shown). Plantar pain was the most importantfeature of PC affecting quality of life (see below).

Other common clinical findings in PCFingernail involvement. As shown in Fig 3,

thickened fingernails were reported in 220 of 254(87%) patients (Table II). The prevalence was lowerin the other mutation carriers, with 9 of 20 (45%)KRT6B and 56 of 76 (74%) KRT16 mutation carriersreporting at least one affected nail (Table II).Interestingly, when the number of fingernails af-fected was evaluated based on mutation type, pa-tients with KRT6B mutations appeared to have far

Table I. International Pachyonychia CongenitaResearch Registry demographics

No. of individuals

Mode of inheritanceFamilial 157Spontaneous 97

GenderMale 121Female 133

Location of residenceUnited States 125Outside United States 129

Age, yMedian 33Range \1-86

J AM ACAD DERMATOL Eliason et al 3

fewer nails affected on average compared with thosewith other keratin gene mutations. Comparison ofthe OR to develop fingernail involvement later thanKRT6A mutation carriers revealed a statistically sig-nificantly elevated OR for KRT6B and KRT16 but notfor KRT17 carriers.

Mucosal involvement. Oral leukokeratosis wasreported in 177 of 254 individuals (70%) with thebreakdown by mutation noted in Table II. Of the 177individuals with self-identified oral leukokeratosis,125 reported an average age of onset of 5.1 yearswith a median and mode of 0 years. Onset at birthwas reported by 67 of 125 (54%), whereas 84 of 115(73%) reported onset affected by 1 year of age and119 of 125 (95%) by age 20 years (data not shown).KRT6A and KRT17 carriers had a significantly in-creased OR of earlier onset of oral leukokeratosiscompared with KRT6B and KRT16 carriers.

Cysts. Pilosebaceous cysts and steatocysts havebeen reported in conjunction with PC types 1 and 2.Overall, 104 of 254 (41%) patients reported cysts ofany type (Table II). KRT17 mutation carriers had a

much higher likelihood of reporting cysts (OR of 23.2[P = .003]) compared with KRT6A mutation carriers.

Natal teeth. The phenomenon of erupted teethpresent at birth known as ‘‘natal teeth’’ has beenreported in patients with PC. Of the 39 patients whoreported the presence of teeth at birth, 36 wereKRT17 mutation carriers. No KRT16 or KRT6B mu-tation carriers reported natal teeth and only 3 of 115(3%) KRT6A carriers were affected (Table II).

PC reduces the quality of lifeIn Table III the severity and frequency of common

PC symptoms are detailed.Of the 240 patients who reported plantar pain, 214

indicated its frequency. A total of 138 (64%) indicatedthat their quality of life was affected at least weeklyby plantar pain. In all, 41 (20%) of respondents wereaffected ‘‘every month or two’’; 26 (12%) reportedbeing affected ‘‘seldom’’ (defined as ‘‘once a year orless’’); and 9 (4%) indicated that they were neveraffected. Describing the pain, 99 of 240 (41%)reported it was ‘‘very painful, but do not use

Table II. Prevalence of selected clinical features in pachyonychia congenita

Phenotype

Keratin gene affected

Total

N = 254

KRT6A

N = 115

KRT16

N = 76

KRT6B

N = 20

KRT17

N = 43

Thick toenails 249/254 (98%) 115/115 (100%) 71/76 (93%) 20/20 (100%) 43/43 (100%)Plantar keratoderma 241/254 (95%) 105/115 (91%) 76/76 (100%) 20/20 (100%) 40/43 (93%)Plantar pain 225/254 (89%) 101/115 (88%) 72/76 (95%) 20/20 (100%) 32/43 (74%)Thick fingernails 220/254 (87%) 115/115 (100%) 56/76 (74%) 9/20 (45%) 40/43 (93%)Oral leukokeratosis 177/254 (70%) 111/115 (97%) 45/76 (59%) 7/20 (35%) 14/43 (33%)Palmar keratoderma 149/254 (59%) 60/115 (52%) 63/76 (83%) 6/20 (30%) 20/43 (30%)Follicular hyperkeratosis 140/254 (55%) 88/115 (77%) 10/76 (13%) 7/20 (35%) 35/43 (81%)Hyperhidrosis 124/254 (49%) 60/115 (52%) 33/76 (43%) 10/20 (50%) 21/43 (49%)Cysts 104/254 (41%) 47/115 (41%) 8/76 (11%) 11/20 (55%) 38/43 (88%)Hoarseness 71/254 (28%) 49/115 (45%) 15/76 (20%) 7/20 (35%) 10/43 (23%)Natal teeth 39/254 (15%) 3/115 (3%) 0/76 (0%) 0/20 (0%) 36/43 (84%)

Fig 1. Clinical phenotype in genetically confirmed pachyonychia congenita. Toenail involve-ment usually demonstrates significant subungual hyperkeratosis and sometimes presents withpremature termination of nail.


medication’’; 62 of 240 (26%) answered that they‘‘often require medication for the pain’’; and 79 of240 (33%) reported that plantar pain was ‘‘somewhatto not painful.’’

DISCUSSIONThis cohort includes patients with the 4 most

common PC keratin mutations in sufficient numbersto draw conclusions regarding the prevalence andpenetrance of the most common PC clinical findings.To out knowledge, it includes the most diversecollection of patients of any cohort thus far evaluatedand reduces the impact of genetic background orfounder bias among the clinical features reported fordifferent mutations.

Because of difficulties inherent in the study of arare genodermatosis there are several limitationswith our data. The patients were ascertained eitherby self- or physician-referral, not from a population-based assessment. Because most self-referrals werefrom individuals who became aware of PC throughthe Internet, our cohort probably represents a moreaffluent, better-educated population with access tohealth care. Because of the geographically dispersednature of the cohort, our data were mostly gatheredthrough telephone interviews and evaluation ofphotographs, rather than by direct examination,which makes the objective quantification of clinicalseverity more difficult. The quality-of-life measuresand reporting of pain, although key to

Fig 2. Clinical phenotype in genetically confirmed pachyonychia congenita. Plantar hyper-keratosis often follows pressure distribution, but can involve entirety of plantar surface.Environmental factors play significant role in development and persistence of plantarkeratoderma.

Fig 3. Clinical phenotype in genetically confirmed pachyonychia congenita. Fingernailfindings include dramatic elevation of fingernails because of subungual debris or prematuretermination of nail plate.


understanding the most important issues that affectpatients with PC, were not performed using a vali-dated metric.

The most common clinical findings in our PCcohort were toenail thickening, plantar keratoderma,and plantar pain. Only one patient, who was youn-ger than 1 year, lacked all 3 findings. The impact ofage on their prevalence is significant as childrenseldom develop plantar keratoderma or plantar painbefore they start to walk. If children 3 years of ageand younger were excluded from the analysis, 216 of230 (94%) individuals would meet all 3 criteria and227 of 230 (99%) of our participants would have mettwo criteria. For the clinician, these findings suggestthat the presence of toenail dystrophy with plantarkeratoderma and plantar pain in children older than3 years is a much more sensitive means of clinicallydiagnosing PC than 20-nail dystrophy, which is oftenthought to be requisite to the diagnosis.

Additional diagnostic findings associated with PCincluded fingernail dystrophy, follicular hyperkera-tosis, leukokeratosis, cysts, and natal teeth. Lesscommon findings included ear pain, hoarseness,and hyperhidrosis. In the literature there are reportsof corneal findings, deafness, skeletal abnormalities,andmental retardation associated with PC. We foundno support for these findings among our cohort. Amore detailed discussion of features spuriously as-sociated with PC will be reported elsewhere.

Although a detailed discussion of the clinicalfindings linked to a specific mutation is beyond thescope of this article, we found that the KRT16mutations, p.Asn125Ser and p.Arg127Cys, werestrongly associated with lack of fingernail involve-ment whereas KRT16 mutation carriers with thep.Leu132Pro mutation frequently presented with10-fingernail dystrophy. Our group has recentlypublished a large study reviewing new and previ-ously known mutations in patients with PC.24 Asmore data are gathered we hope to be able toprovide phenotypic prognosis based on the specificmutation identified.

Plantar pain has the most profound effect onquality of life for most patients with PC as it can limitmobility and social interaction along with the ability

to find and maintain work. The pain reported bypatients with PC is often out of proportion to theextent or duration of callus, suggesting that themechanism is not merely the result of pressurefrom callus formation. Clinicians will better meetthe needs of patients with PC by inquiring about theextent of pain and helping them manage theircalluses to facilitate pain reduction.

Historically, PC has been subdivided into twomajor phenotypic variants, PC-1 (Jadassohn-Lewandowski) and PC-2 (JacksoneLawler). ThePC-1/PC-2 classification was designed to improvethe ability to predict phenotypic prognosis withoutgenetic testing. The PC-1/PC-2 classification assumesthat because certain keratin proteins predictablydimerize that a mutation in either protein gene willresult in a similar clinical phenotype. Hence, amutation in either of the PC-1 keratin proteins(K6a/K16) should cause similar features, whereas amutation in K6b/K17 (PC-2 proteins) will presentwith a different, predictable phenotype.

Instead, our data demonstrated that clinical phe-notypes overlapped substantially across genotypiccategories and could not be used to predict genotypereliably. Specifically, we found a significant overlapof oral leukokeratosis, cysts, and natal teeth thatpurportedly distinguish PC-1 and PC-2. Overall, ourdata demonstrate that the PC-1/PC-2 nomenclaturedoes not accurately reflect the molecular pathogen-esis of PC and does not represent a rational orclinically useful classification at this time.

We recommend the elimination of the terms‘‘PC-1’’ and ‘‘PC-2’’ and propose their replacementwith notation of the specific keratin defect. In thisclassification scheme a diagnosis of PC-6a, PC-6b,PC-16, and PC-17 would correspond to mutations inthe KRT6A, KRT6B, KRT16, and KRT17 genes,respectively. A designation of PC-U (unknown)may be applied when the classic clinical findings ofPC are found in the absence of a known PC keratingene mutation. Classification based on keratin mu-tation subtype will allow clinicians to provide moreaccurate prognoses for patients with PC. We recom-mend genetic testing for individuals with the triad oftoenail dystrophy, plantar keratoderma, and plantar

Table III. Impact of specific features of pachyonychia congenita on quality of life

Impact on quality of life Plantar keratoderma Thickened toenails Cysts Thickened fingernails Oral leukokeratosis

No impact 19/216 (9%) 71/221 (32%) 63/154 (41%) 67/199 (34%) 40/64 (63%)Sometimes a problem 56/216 (26%) 113/221 (51%) 65/154 (42%) 109/199 (55%) 23/64 (35%)Always a problem, butable to function

133/216 (62%) 36/221 (16%) 23/154 (15%) 22/199 (11%) 1/64 (2%)

Unable to function 8/216 (4%) 1/221 (0.5%) 3/154 (2%) 1/199 (0.5%) 0/64 (0%)


pain as they have a high likelihood of carrying a PCmutation. Genetic testing is provided free of chargeto all patients who enroll in the PC registry throughthe nonprofit patient advocacy group, PachyonychiaCongenita Project (www.pachyonychia.org).

We look forward to the development of specificgenetic techniques to minimize or eliminate theclinical expression of this rare keratin disorder.25-27

REFERENCES

1. Smith FJD, Kaspar RL, Schwartz ME, McLean WHI, Leachman

SA. Pachyonychia congenita. GeneReviews 2006. Available

from: URL: http://www.genetests.org/profiles/pc. Accessed

October 15, 2010.

2. Leachman SA, Kaspar RL, Fleckman P, Florell SR, Smith FJ,

McLean WH, et al. Clinical and pathological features of pachy-

onychia congenita. J InvestigDermatol SympProc 2005;10:3-17.

3. McLean WH, Rugg EL, Lunny DP, Morley SM, Lane EB,

Swensson O, et al. Keratin 16 and keratin 17 mutations cause

pachyonychia congenita. Nat Genet 1995;9:273-8.

4. Bowden PE, Haley JL, Kansky A, Rothnagel JA, Jones DO,

Turner RJ. Mutation of a type II keratin gene (K6a) in


5. Smith FJ, Jonkman MF, van Goor H, Coleman CM, Covello SP,

Uitto J, et al. A mutation in human keratin K6b produces a

phenocopy of the K17 disorder pachyonychia congenita type

2. Hum Mol Genet 1998;7:1143-8.

6. Kaspar RL. Challenges in developing therapies for rare diseases

including pachyonychia congenita. J Invest Dermatol Symp

Proc 2005;10:62-6.

7. Muller C. Zur Kasuistic der kongenitalen onchogryphosis [On

the causes of congenital onychogryposis]. Muenchener Med-

izinische Wochenschrift 1904;49:2180-2.

8. Wilson AG, Cantar MB. Three cases of hereditary hyperkerato-

sis of the nail-bed. Br J Dermatol 1904;17:13-4.

9. Jadassohn J, Lewandowski P. Pachyonychia congenita: kera-

tosis disseminata circumscripts (follicularis). Tylomata. Leuko-

keratosis linguae. In: Neisser A, Jacobi E, editors. Ikonographia

dermatologica. Berlin: Urban and Schwarzenberg; 1906. pp.

29-31.

10. Kumer L, Loos HO. Ueber pachyonychia congenita (typus

Riehl) [On pachyonychia congenita (Riehl type)]. Wien Klin

Wochenschr 1935;48:174-8.

11. Moldenhauer E, Ernst K. Das Jadassohn-Lewandowsky-

syndrom [The Jadassohn-Lewandowsky syndrome]. Hautarzt

1968;19:441-7.

12. Schonfeld PH. The pachyonychia congenita syndrome. Acta

Derm Venereol 1980;60:45-9.

13. Franzot J, Kansky A, Kavcic S. Pachyonychia congenita

(Jadassohn-Lewandowsky syndrome): a review of 14 cases in

Slovenia. Dermatologica 1981;162:462-72.

14. Stieglitz JB, Centerwall WR. Pachyonychia congenita (Jadas-

sohn-Lewandowsky syndrome): a seventeen-member,

four-generation pedigree with unusual respiratory and dental

involvement. Am J Med Genet 1983;14:21-8.

15. Sivasundram A, Rajagopalan K, Sarojini T. Pachyonychia

congenita. Int J Dermatol 1985;24:179-80.

16. Feinstein A, Friedman J, Schewach-Millet M. Pachyonychia

congenita. J Am Acad Dermatol 1988;19:705-11.

17. Su WP, Chun SI, Hammond DE, Gordon H. Pachyonychia

congenita: a clinical study of 12 cases and review of the

literature. Pediatr Dermatol 1990;7:33-8.

18. Paller AS, Moore JA, Scher R. Pachyonychia congenita tarda: a

late-onset form of pachyonychia congenita. Arch Dermatol

1991;127:701-3.

19. Dahl PR, DaoudMS, Su WP. Jadassohn-Lewandowski syndrome

(pachyonychia congenita). Semin Dermatol 1995;14:129-34.

20. Munro CS, Carter S, Bryce S, Hall M, Rees JL, Kunkeler L, et al. A

gene for pachyonychia congenita is closely linked to the

keratin gene cluster on 17q12-q21. J Med Genet 1994;31:

675-8.

21. van Steensel MA, Jonkman MF, van Geel M, Steijlen PM,

McLean WH, Smith FJ. Clouston syndrome can mimic pach-

yonychia congenita. J Invest Dermatol 2003;121:1035-8.

22. Munro CS. Pachyonychia congenita: mutations and clinical

presentations. Br J Dermatol 2001;144:929-30.

23. Wilson NJ, Messenger AG, Leachman SA, O’Toole EA, Lane EB,

McLean WH, et al. Keratin K6c mutations cause focal palmo-

plantar keratoderma. J Invest Dermatol 2010;130:425-9.

24. Wilson NJ, Leachman SA, Hansen CD, McMullan AC, Milstone

LM, Schwartz ME, et al. A large mutational study in pachyo-

nychia congenita. J Invest Dermatol 2011;131:1018-24.

25. Leachman SA, Hickerson RP, Hull PR, Smith FJ, Milstone LM,

Lane EB, et al. Therapeutic siRNAs for dominant genetic skin

disorders including pachyonychia congenita. J Dermatol Sci

2008;51:151-7.

26. Leachman SA, Hickerson RP, Schwartz ME, Bullough EE,

Hutcherson SL, Boucher KM, et al. First-in-human

mutation-targeted siRNA phase Ib trial of an inherited skin

disorder. Mol Ther 2010;18:442-6.

27. Hickerson RP, Smith FJ, Reeves RE, Contag CH, Leake D,

Leachman SA, et al. Single-nucleotide-specific siRNA targeting

in a dominant-negative skin model. J Invest Dermatol 2008;

128:594-605.


ORIGINAL ARTICLE

Best treatment practices for pachyonychia congenitaI. Goldberg,1,* D. Fruchter,1 A. Meilick,1 M.E. Schwartz,2 E. Sprecher1

1Department of Dermatology, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel2Pachyonychia Congenita Project, Salt Lake City, UT, USA

*Correspondence: I. Goldberg. E-mail: [email protected]

AbstractBackground Numerous therapeutic modalities have been proposed to treat the manifestations of pachyonychia con-

genita (PC). While research hopes lie with molecular therapies, patients are in need of answers regarding the efficacy of

conventional treatments.

Aim of the study To determine patients’ experience and preferences regarding conventional treatments for PC.

Methods The study population included 120 PC patients from 20 countries. The study was based on a patient survey

developed by physicians and researchers from the International Pachyonychia Congenita Consortium and conducted

via the internet. Using an effectiveness scale of 1 to 5, the patients were asked to grade treatments for different manifes-

tations, including keratoderma, cysts, follicular hyperkeratosis, fingernail and toenail involvement.

Results Patients reported surgical treatments being most effective for cysts and mechanical treatments the most

effective conventional therapeutic approach for all other investigated manifestations. The other conventional medical

treatments were found to be non-effective to only slightly effective. Among patients with keratoderma, older people were

more likely to report beneficial effect from mechanical treatments (P = 0.04), topical retinoids (P = 0.04) and topical ste-

roids (P = 0.02). Likewise, females were more inclined to report filing and grinding beneficial than males (P = 0.02).

Finally, carriers of KRT16 and KRT6a were more likely to benefit from keratolytics than carriers of mutations in KRT17

(P = 0.04).

Conclusions None of the currently available therapeutic options for PC are ideal, although they provide some relief,

with mechanical/surgical options being preferred over medical therapies. These results emphasize the need for more effi-

cient and targeted therapies.

Received: 5 July 2012; Accepted: 18 December 2012

Conflict of interestNone declared.

Funding sourcesFunded by the Pachyonychia Congenita Project.

IntroductionPC is a very rare keratinizing disorder estimated to affect

between 5 and 10 thousand people worldwide.1 This disorder

is transmitted as an autosomal dominant trait, and is caused

by mutations in one of five keratin genes: KRT6A, KRT6B,

KRT6C, KRT16, KRT17, which encode keratins K6a, K6b,

K6c, K16 and K17 respectively.1,2 Most of the keratin muta-

tions which cause PC are heterozygous missense mutations or

small insertions/deletions which result in fragility of the epi-

thelial cell cytoskeleton, leading to cell cytolysis and tissue

blistering or hyperkeratosis.2–4

PC cardinal features were first reported by Muller5 and

Wilson6 in 1904, and by Jadassohn and Lewandowski in

1906,7 and include painful and debilitating plantar keratoder-

ma, hypertrophic toenail and fingernail dystrophy, follicular

hyperkeratosis, palmar keratoderma, epidermal cysts, oral leu-

kokeratosis, and occasionally hyperhidrosis, hoarseness and

natal teeth.1,2

Clinical classification of PC variants was first suggested by

Kumer in 1935.8 PC was eventually divided into two clinical sub-

types: the Jadassohn-Lewandowski PC (type-1 PC) and the

Jackson-Lawler PC (type-2 PC).1,2

This clinical classification was intended to assist estimation of

the prognosis in the absence of genetic testing.1,2 After the dis-

covery of the underlying cause of PC, genotype-phenotype anal-

ysis suggested initially that mutations in KRT6a/KRT16 and

KRT6b/KRT17 were associated with type 1 and type 2 PC

respectively.1 More recently, large-scale genetic analysis raised

doubts regarding the clinical relevance of these correlations,1,2

leading to the establishment of a novel classification for PC

© 2013 The AuthorsJournal of the European Academy of Dermatology and Venereology © 2013 European Academy of Dermatology and VenereologyJEADV 2013

DOI: 10.1111/jdv.12098 JEADV

based solely on molecular analysis resulting in PC-K6a, PC-K6b,

PC-K6c, PC-K16 and PC-K17 as distinct types.1,2

Many therapeutic modalities have been proposed to treat

the various clinical manifestations in PC, including retinoids,9

surgical and mechanical procedures, orthotics, keratolytics,

pain medications10 and botulinum toxin.11 Recently, more

targeted therapeutic strategies (including small interfering

RNAs,12–14 rapamycin15 and simvastatin16) have been the

focus of much attention. Unfortunately, as most of these

advanced approaches still cannot be offered on a routine

basis to patients because of expense and limited availability,

patients are currently forced to rely upon the use of the

available conventional strategies.

In this study, we used a patient survey approach to derive

effectiveness data in PC. This methodology has been widely used

over the past years to delineate guidelines for the treatment of

disorders for which no controlled data are available.9

Methods

PatientsThe study population included pachyonychia congenita patients

from 20 different countries who were enrolled in the Interna-

tional Pachyonychia Congenita Research Registry (IPCRR) and

recruited through Pachyonychia Congenita Project, a non-profit

patient advocacy group established in 2004.1,2 All patients were

diagnosed using a detailed clinical questionnaire and genetic

testing results for a mutation in one of the PC-associated genes.

The study was conducted according to the principles of the dec-

laration of Helsinki and all patients gave their written informed

consent.

Data collectionIn addition to the extensive physician-validated data in the

IPCRR, each patient completed an addendum survey via the in-

ternet providing information on treatments used for five catego-

ries of clinical manifestations of PC: keratoderma, cysts,

follicular hyperkeratosis, fingernail and toenail involvement. In

addition, all patients provided information on demographics,

genetic status, the effect of the disease on their quality of life, the

clinical manifestations of PC and the degree of effectiveness of

the different treatments.

The patients were asked to grade each treatment they had

used according to a treatment effectiveness scale of 1 to 5:

1- not effective at all

2- a little effective

3- somewhat effective

4- effective

5- very effective.

The patients were asked to grade different available treat-

ments including mechanical treatments (such as filing, grind-

ing, cutting, clipping or plucking the lesions), surgical

removal of the lesions, surgical removal of the nail, incision

and drainage of cysts, soaking of the nails to soften them

before treatments, orthotics, custom made orthotics, topical

and oral retinoids, pain medications, botulinum toxin, mois-

turizers, vaseline, keratolytic treatments, antibiotic ointments,

antifungal ointments, topical and oral steroids, salicylic acid,

treatments of the nails by medical professional and treatments

of the nails in a nail salon.

Statistical analysisAll outcome variables are ordinal variables ranging from 1 to 5 –

the higher the score, the higher the treatment effect. Univariate

analysis was used to determine the relationships between each

explanatory variable and the treatment outcome variables. The

explanatory variables are the following: age, gender, quality of

life score (QOL) and gene (categorical variable).

Pearson correlations were calculated between all continuous

explanatory variables and the outcome variables. Wilcoxon Two-

Sample or Kruskal–Wallis tests were used to compare between

categorical explanatory variables and the outcome variables.

A P-value of 0.05 was considered significant. Statistical analy-

sis was performed by SAS for windows version 9.2 (SAS Insti-

tute, Cary, NC, USA).

ResultsThe study included 120 PC patients, 67 females and 53 males, of

all ages. The youngest patient was a 1-year-old baby and the old-

est an 81-year-old patient. The average age was 38.5, and the

median age was 39 years.

KeratodermaOf the 120 patients who took part in the study, 113 patients

reported having keratoderma. Forty-eight patients had clinical

manifestations involving both palms and soles; 65 patients had

only sole involvement.

Most conventional treatments were attributed mean scores of

2 to 3 (a little effective to somewhat effective) (Fig. 1). Patients

reported mechanical treatments (such as filing, grinding, cutting,

clipping), as the most effective conventional treatments corre-

sponding to a mean score of 3.8. Pain control medications and

orthotics ranked second in effectiveness.

Other medications such as antibiotic ointments, urea cream,

oral and topical retinoids, oral and topical steroids, botulinum

toxin injections, salicylic acid or antifungal treatments were

reported as poorly effective.

CystsOf the 120 patients who took part in the study, 49 patients

reported having cysts (Fig. 2). Surgical removal treatment was

found to be effective to very effective, reaching a mean score of

4.32. The next most effective treatment reported was incision

and drainage with a mean score of 4. Pain medications were


2 Goldberg et al.

found to be of little effect. Other treatments, such as antibiotic

ointments, intralesional and oral steroids and retinoids, were

reported as not effective.

Follicular hyperkeratosisOf the 120 patients who took part in the study, 63 patients

reported being affected with follicular hyperkeratosis. The

results (Fig. 3) showed that the available conventional treat-

ments for follicular hyperkeratosis were slightly effective or

not effective, with clipping or plucking the plugs leading with

a mean score of 2.9.

Toenail involvementToenail involvement is very common in PC. Of the 120 patients

in the study, 108 patients reported toenail involvement. The

results for toenail involvement (Fig. 4) demonstrated that the

most effective approach was mechanical treatment such as filing,

grinding, cutting or clipping the toenails. Mechanical treatment

received a mean score of 4. The patients reported that the second

most effective treatment, with a mean score of 3.6, was soaking

the nails to soften them before treatment. Of note, surgical avul-

sion of the nail was found to be ineffective, as were non-medical

treatments provided in nail salons.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

3.8

3.0 3.02.7 2.6 2.5 2.5

2.2 2.1 2.1 2.1 1.9 1.9 1.71.3 1.3

1.1Effe

ctiv

enes

s sc

ore

Mean scores of treatment effect in keratoderma

Figure 1 Mean scores of effectiveness of the different treatments used for keratoderma (reported by 113 patients). Treatment effective-ness is represented by a colour scale: red - not effective treatment (scores between 1 and 2), orange - mildly effective treatment (scoresbetween 2 and 3), green - somewhat effective treatment (scores between 3 and 4), blue - effective treatment (scores between 4 and 5).

00.5

11.5

22.5

33.5

44.5

5 4.324

2.38 2.2

1.6 1.5 1.4 1.3 1.25

Effe

ctiv

enes

s sc

ore

Mean scores of treatment effect in cysts

Figure 2 Mean scores of effectiveness of the different treatments for cysts (reported by 49 patients). Treatment effectiveness colourscale is described in figure legend 1.


Treatment for pachyonychia congenita 3

Fingernail involvementFingernail involvement was reported by 94 of the 120 patients in

this study. Results pertaining to fingernail involvement resem-

bled those obtained for toenail involvement (Fig. 5).

The most effective treatment was mechanical treatment

such as grinding, filing, clipping or cutting the fingernails.

Mechanical treatments received a mean score of 4 and the

second most effective treatment was soaking and softening

the nails. The other treatments ascertained were found to be

not effective.

Univariate analysisAs multivariate analysis was found to be very unstable due to the

wide range of available data, we used univariate analysis to

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

2.9

2.472.19 2.13

1.67 1.561.33

Effe

ctiv

enes

s sc

ore

Mean scores of treatment effect in follicular hyperkeratosis

Figure 3 Mean scores of effectiveness of the different treatments used for follicular hyperkeratosis (reported by 63 patients). Treatmenteffectiveness colour scale is described in figure legend 1.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

4.06

3.67

3.14

2.34 2.25 2.212.07 2

1.66 1.61 1.61.47E

ffect

iven

ess

scor

e

Mean scores of treatment effect in toenail involvement

Figure 4 Mean scores of effectiveness of the different treatments used for toenail involvement (reported by 108 patients). Treatmenteffectiveness colour scale is described in figure legend 1.


4 Goldberg et al.

further analyse the data and to determine the relationships

between each explanatory variable and the treatment outcome

variables. This analysis revealed three facts of clinical relevance

for patients with keratoderma:

1 As patients grew older, they were more likely to report benefi-

cial effect from mechanical interventions (such as filing,

grinding) (P = 0.04), topical retinoids (P = 0.04) and topical

steroids (P = 0.02).

2 Females were more inclined than males (P = 0.02) to

describe mechanical interventions such as filing and grinding

as beneficial.

3 Finally, carriers of mutations in KRT16 and KRT6a were

more likely to benefit from keratolytics than carriers of muta-

tions in KRT17 (P = 0.04).

DiscussionTreating PC is challenging. PC is clinically multifaceted and the

conventional treatments are directed at the different manifesta-

tions of the disorder. Currently, there are no specific treatments

for PC.16,17 Each patient presents a unique constellation of con-

ditions and a treatment plan must be individually tailored.17

Unfortunately, despite use of numerous approaches to relieve

PC-associated symptoms, little is currently known regarding

their relative efficacy.

Conventional treatment for nail disease in PC includes

mechanical or surgical procedures, such as grooming or surgical

removal of nails. The nails tend to re-grow unless complete

ablation is performed. Follicular hyperkeratosis can be treated

by oral and topical retinoids, keratolytic agents and alpha-

hydroxy acid preparations. Cysts may be treated by incision,

excision, drainage or by intralesional injection of steroids. In

case of infection, oral antibiotics may be indicated.10

Currently, retinoids are considered efficient drugs to treat

hyperkeratotic disorders including PC.9,16 They act via retinoic

acid response elements (RAREs) which are present in the kera-

tin’s gene promoters, and inhibit gene expression.16 Retinoids,

although reducing hyperkeratosis, may also cause thinning of

the epidermis and blistering, leading to pain and possible infec-

tious complications.10,16,18 Contradictory data regarding the effi-

cacy of retinoids in PC have been published. Some case reports

demonstrated an improvement of calluses with retinoid treat-

ment.19–22 Other studies described patients with improvement

of hyperkeratosis with retinoid treatment, but no change in

pachyonychia.21,22 More recently, Gruber et al.9 analysed data

collected in 30 PC patients who received systemic retinoid treat-

ment. They found that 50% and 14% of their patients reported

improvement in palmoplantar hyperkeratosis and pachyonychia

respectively. The mean satisfaction score from the treatment was

found to be 4.5 on a scale of 1–10. All patients reported suffering

from adverse effects and 83% stopped using the drug.9 In con-

trast with these mixed results, others have reported no improve-

ment with retinoids in PC23,24 and, in another series,25 four

patients with palmoplantar keratoderma who received oral reti-

noids reported improvement in the appearance of their skin, but

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

4.01

3.253

2.52.32

2.172.05

1.821.6

1.4 1.38

1.08

erocsssenevitceffE

Mean scores of treatment effect in fingernail involvement

Figure 5 Mean scores of effectiveness of the different treatments used for fingernail involvement (reported by 94 patients). Treatmenteffectiveness colour scale is described in figure legend 1.



had to stop the treatment because of pain that restricted hand

and foot function.

Levels of evidence vary according to the methodology used in

clinical studies, which in turn is often a function of patient pop-

ulation size. Randomized control studies are of course prefera-

ble; however, in diseases as infrequent as PC, such studies are

not always possible.9,18 Alternative methodologies, also adapted

to rare conditions in which controlled studies cannot be readily

performed, rely upon the quantification of patient values and

expectations.

Our study was based on a survey conducted among the largest

group of PC patients ascertained to date for treatment efficacy.

As all patients had been diagnosed with PC on the basis of both

a careful physical examination and a full molecular analysis, we

believe that the data collected faithfully reflect PC patients’

appreciation of conventional therapeutic modalities.

We found that the majority of conventional treatments were

only marginally effective for keratoderma, with mechanical treat-

ments being the most effective.

Palmoplantar keratoderma is a very common manifestation

of PC, usually presenting as a child starts walking and bearing

weight during the first few years of life.10 In a study by Eliason,

et al.1 plantar keratoderma was present in 241 of 254 (95%) of

patients. Of the 13 patients reported as not having plantar kera-

toderma, the oldest was 3-years old and nine were younger than

1 year. Among 241 patients who reported having plantar kerato-

derma, the age of onset ranged from birth to 30 years and the

average age was 4.2 years. In our study, most of the patients who

did not report plantar keratoderma were younger than 5 years

of age.

Patients reported surgical treatments being most effective for

cysts. Mechanical treatments were found to be the most effective

conventional therapeutic approach for follicular hyperkeratosis,

as well as for toenail and fingernail involvement. The other con-

ventional medical treatments were found to be non-effective to

only slightly effective.

In line with a previous study,26 keratolytics, which are widely

used by the patients, were found to be of limited effectiveness

for both palmoplantar keratoderma and nail problems.

Response to treatment was highly individual, underscoring

the need for clinical or molecular predictors of response to ther-

apy. In this regard, the results of our univariate analysis, which

remain to be independently confirmed, suggest a number of

such predictive parameters. For example, our finding that carri-

ers of mutations in KRT16 and KRT6a were more likely to bene-

fit from keratolytics than carriers of mutations in KRT17 may be

explained by the fact that the latter group has milder kerato-

derma than the former groups.1 This finding is consistent with

phenotypic differences.

Overall, current available therapeutic approaches in PC are of

borderline benefit. Therefore, the recent major advances in the

search for PC-specific therapeutic strategies are of great impor-

tance. For example, a mutation-specific siRNA was found

recently to lead to callus recession and pain control in a PC

patient.12–14,16 However, these injections were found to be tre-

mendously painful underscoring the need for new approaches

for more efficient and practical ways of nucleic acid delivery to

the skin.27 Other treatments under investigation for PC patients

are rapamycin and simvastatin, but these therapies, although

providing hope for patients, are not yet applied routinely.10,15,16

In conclusion, although none of the currently available thera-

peutic approaches seem to be ideal, they do provide some relief

to our patients. Mechanical/surgical options are preferred over

medical therapies, such as retinoids, antibiotics or antifungal

agents. These results emphasize the need for more efficient and

targeted therapies.

AcknowledgementsWe thank patients and their families in the International Pachy-

onychia Congenita Research Registry (IPCRR) for their support

and members of the International Pachyonychia Congenita Con-

soritum (IPCC) for development of the treatment survey.

References1 Eliason MJ, Leachman SA, Feng BJ, Schwartz ME, Hansen CD. A review

of the clinical phenotype of 254 patients with genetically confirmed

pachyonychia congenita. J Am Acad Dermatol 2012; 67: 680–686.2 McLean WH, Hansen CD, Eliason MJ, Smith FJ. The phenotypic and

molecular genetic features of pachyonychia congenita. J Invest Dermatol

2011; 131: 1015–1017.3 McLean WH, Smith FJ, Cassidy AJ. Insights into genotype-phenotype

correlation in pachyonychia congenita from the human intermediate

filament mutation database. J Investig Dermatol Symp Proc 2005; 10:

31–36.4 McLean WH, Moore CB. Keratin disorders: from gene to therapy. Hum

Mol Genet 2011; 20: R189–R197.5 Muller C. Zur Kasuistic der kongenitalen onchogryphosis [on the causes

of congenital onychogryposis]. Muenchener Medizinische Wochenschrift

1904; 49: 2180–2182.6 Wilson AG, Cantar MB. Three cases of hereditary hyperkeratosis of the

nail-bed. Br J Dermatol 1904; 17: 13–14.7 Jadassohn J, Lewandowski P. Pachyonychia congenita: keratosis dissemi-

nate circumscripts (follicularis). Tylomata. Leukokeratosis linguae. In

Neisser A, Jacobi E, eds. Ikonographia Dermatologica. Urban and Sch-

warzenberg, Berlin, 1906: 29–31.8 Kumer L, Loos HO. Ueber pachyonychia congenita (typus Riehl)[on

pachyonychia congenita (Riehl type)]. Wien Klin Wochenschr 1935; 48:

174–178.9 Gruber R, Edlinger M, Kaspar RL et al. An appraisal of oral retinoids in

the treatment of pachyonychia congenita. J Am Acad Dermatol 2012; 66:

e193–e199.10 Smith FJD, Hansen CD, Hull PR et al. Pachyonychia congenita. In Pa-

gon RA, Bird TD, Dolan CR, Stephens K, Adam MP, eds. GeneRe-

viewsTM [Internet], University of Washington, Seattle, Seattle (WA),

2006.

11 Swartling C, Karlqvist M, Hymnelius K, Weis J, Vahlquist A. Botulinum

toxin in the treatment of sweat-worsened foot problems in patients with

epidermolysis bullosa simplex and pachyonychia congenita. Br J Dermatol

2010; 163: 1072–1076.12 Kaspar RL, Leachman SA, McLean WH, Schwartz ME. Toward a treat-

ment for pachyonychia congenita: report on the 7th Annual International


6 Goldberg et al.

Pachyonychia Congenita Consortium meeting. J Invest Dermatol 2011;

131: 1011–1014.13 Hickerson RP, Smith FJD, Reeves RE et al. Single-nucleotide-specific siR-

NA targeting in a dominant-negative skin model. J Invest Dermatol 2008;

128: 594–605.14 Leachman SA, Hickerson RP, Hull PR et al. Therapeutic siRNAs for dom-

inant genetic skin disorders including pachyonychia congenita. J Dermatol

Sci 2008; 51: 151–157.15 Hickerson RP, Leake D, Pho LN, Leachman SA, Kaspar RL. Rapamycin

selectively inhibits expression of an inducible keratin (K6a) in human

keratinocytes and improves symptoms in pachyonychia congenita

patients. J Dermatol Sci 2009; 56: 82–88.16 Zhao Y, Gartner U, Smith FJ, McLean WH. Statins downregulate K6a

promoter activity: a possible therapeutic avenue for pachyonychia con-

genita. J Invest Dermatol 2011; 131: 1045–1052.17 Milstone LM, Fleckman P, Leachman SA et al. Treatment of pachyony-

chia congenita. J Investig Dermatol Symp Proc 2005; 10: 18–20.18 Ormerod AD, Campalani E, Goodfield M. British Association of Derma-

tologists guidelines on the efficacy and use of acitretin in dermatology.

Br J Dermatol 2010; 162: 952–963.19 Dupr�e A, Christol B, Bonaf�e JL, Touron P. [Pachyonychia congenita.

Three familial cases. Effects of the treatment by aromatic retinoid (RO

10.9359)]. Ann Dermatol Venereol 1981; 108: 145–149. [French].

20 Carabott F, Archer CB, Griffiths WA. Etretinate-responsive pachyonychia

congenita. Br J Dermatol 1988; 119: 551–553.21 Lim TW, Paik JH, Kim NI. A case of pachyonychia congenita with

oral leukoplakia and steatocystoma multiplex. J Dermatol 1999; 26:

677–681.22 Hoting E, Wassilew SW. [Systemic retinoid therapy with etretinate in

pachyonychia congenita]. Hautarzt 1985; 36: 526–528. [German].

23 Thomas DR, Jorizzo JL, Brysk MM, Tschen JA, Miller J, Tschen EH.

Pachyonychia congenita. Electron microscopic and epidermal glycopro-

tein assessment before and during isotretinoin treatment. Arch Dermatol

1984; 120: 1475–1479.24 Soyuer U, Candan MF. Failure of etretinate therapy in pachyonychia con-

genita. Br J Dermatol 1987; 117: 264.

25 Fritsch P, H€onigsmann H, Jaschke E. Epidermolytic hereditary palmopl-

antar keratoderma. Report of a family and treatment with an oral

aromatic retinoid. Br J Dermatol 1978; 99: 561–568.26 Su WP, Chun SI, Hammond DE, Gordon H. Pachyonychia congenita: a

clinical study of 12 cases and review of the literature. Pediatr Dermatol

1990; 7: 33–38.27 Hickerson RP, Flores MA, Leake D et al. Use of self-delivery siRNAs to

inhibit gene expression in an organotypic pachyonychia congenita model.

J Invest Dermatol 2011; 131: 1037–1044.



THERAPEUTIC HOTLINE

Efficacy of botulinum toxin inpachyonychia congenita type 1:

report of two new cases

J�essica Gonz�alez-Ramos, Elena Sendagorta-Cud�os,

Guillermo Gonz�alez-L�opez, Ander Mayor-Ibarguren,

Rosa Feltes-Ochoa & Pedro Herranz-Pinto

Department of Dermatology, La Paz University Hospital, Madrid, Spain

ABSTRACT: Pachyonychia congenita (PC) is a rare genodermatosis caused by a mutation in keratingenes, which can lead to hypertrophic nail dystrophy and focal palmoplantar keratoderma(predominantly plantar), amongst other manifestations. Painful blisters and callosities, sometimesexacerbated by hyperhidrosis, are major issues that can have a significant impact on patient qualityof life. Many alternative treatments for this condition have been applied with variable and partialclinical response, but a definitive cure for this disease has yet to be discovered. After obtaininginformed consent, two patients with genetically confirmed PC type 1 were treated with plantarinjections of botulinum toxin type A. Both patients showed a marked improvement in pain andblistering with an average response time of one week, a six-month mean duration of effectiveness,and a lack of any side effects or tachyphylaxis.

KEYWORDS: botulinum toxin, hyperhidrosis, pachyonychia congenita

Introduction

Pachyonychia congenital (PC) is a group of auto-somal dominant congenital keratinopathiescaused by mutations in any of five genes: KRT6A,KRT6B, KRT6C, KRT16, or KRT17. With a preva-lence of 1 : 1,00,000 for this condition, there areestimated to be 5,000–10,000 cases worldwide.

Historically PC has been broken down intotwo clinical subtypes: PC type 1 (Jadassohn-Lewandowski) and PC type 2 (Jackson-Lawler), butclinical phenotypes overlap between both types.

PC-1 is characterized by thickened toenailsand fingernails in the first stages, extremely

painful focal areas of hyperkeratosis and blister-ing, particularly on the soles of the feet (plantarkeratoderma), and occasionally by oral leukoker-atosis, follicular hyperkeratosis, laryngealinvolvement, or other ectodermal defects (cystsor natal teeth).

Diagnosis of PC is determined through clinicalexamination and confirmed by molecular genetictesting, which is provided free to all patientsenrolled in the PC registry (PC Project) http://www.pachyonychia.org (1).

Painful foot blistering and callosities are com-mon problems in patients with PC which areoften exacerbated by hyperhidrosis and highambient temperature. Hyperhidrosis can beblocked by plantar injections of botulinum toxin(BTX) (2). We report two patients who experi-enced remarkable improvement in terms ofreduced plantar pain and foot blistering after BTX

Address correspondence and reprint requests to: J�essica

Gonz�alez-Ramos, MD, Department of Dermatology, La Paz

University Hospital, Paseo La Castellana 261, CP 28046,

Madrid, Spain, or email: [email protected].

1

Dermatologic Therapy, Vol. 00, 2015, 00–00

DOI:10.1111/12297VC 2015 Wiley Periodicals, Inc.

DERMATOLOGIC THERAPY

ISSN 1396-0296

http://www.pachyonychia.org


injections without loss of efficacy thus far. Anaes-thesia was achieved in both cases via superficialsedation with spontaneous ventilation.

Case reports

Case 1

The first patient, a 32-year-old woman, had beendiagnosed with PC-1 when she was 3 months old.She presented thickened and discolored nails,focal palmoplantar keratoderma with painful blis-ters and erosions on the soles exacerbated byplantar hyperhidrosis (FIG. 1A), follicular hyper-keratosis on the extensor surfaces of the extrem-ities, oral and laryngeal leukokeratosis causingvocal hoarseness. She had no family history of PCand was otherwise healthy. Foot blisters and cal-losities were so painful that she was unable towalk and required the use of a wheelchair. At theage of 29, blood testing revealed a KRT6A mis-sense mutation (Dundee, Scotland), making thediagnosis of PC type 1 definitive. She had previ-ously been treated with acitretin 25 mg/day,which was later tapered to 10 mg/day, and kera-tolytic agents for more than 10 years with onlypartial effectiveness. In 2010, following informedconsent, she was offered toxin plantar injections.After paring down the callosities by curettage, weadministered intradermal injections of 100 U ofbotulinum toxin type A (BTX-A) (BotoxVR , Allergan,Inc, Irvine, CA) in each sole and 50 U in each

palm. Postinjection clinical improvement beganin week one. Plantar pain and blistering were sig-nificantly mitigated and the patient was able tomobilize without her wheelchair (FIG. 1B). Theeffect of this treatment lasted approximately 6months, so injections were subsequently adminis-tered biannually. In later sessions, the dosage wasreduced (75 U in each sole and 50 U in eachpalm), concentrating the injections below blistersand callosities. The outcome was similar to theprevious technique. Thus, BTX injections have ledto substantial improvement in the patient’s qual-ity of life, allowing her retinoid treatment to bewithdrawn and enabling her to plan a pregnancy.The treatment has shown no reduction in efficacyduring 5 years of follow-up.

Case 2

The second patient, a 27-year-old man, presentedfocal plantar hyperkeratosis with associated hyper-hidrosis, painful blisters on the soles and on theback of the feet (FIG. 2A), thickened nails and oralleukokeratosis. The appearance of lesions beganduring infancy, and at the age of 23, a blood testrevealed a KRT6A missense mutation (Dundee,Scotland). Lesions in palms were less severe. Hehad a son with the condition, although no formalgenetic testing had been conducted on him. Kera-tolytic agents and oral retinoid treatment had pre-viously been applied with poor clinical response.Five months ago we started treatment with BTX-Aat a dose of 150 U for each foot, concentrating the

FIG. 1. Case 1 (A) Focalplantar keratoderma,

blisters, and erosions onthe left plantar surfacebefore botulinum toxin

injections. (B) Improve-ment after plantar injec-

tions of BTX withclearance of blisters anderosions.

Gonz�alez-Ramos et al.

2

injections in the affected areas. A remarkable clini-cal improvement and reduction in plantar painwas seen at Day 7 postinjection (FIG. 2B), with asustained response thus far. He had previouslybeen treated over an 18-month period at anotherhospital with no preinjection curettage of footlesions and a total dose of 100 U, resulting in onlymoderate improvement.

Discussion

Painful plantar hyperkeratosis is a very commonfeature in PC (95% of cases) and the most dis-abling one, reducing quality of life due to plantarpain (1). Currently there is no specific and effec-tive therapy for patients with PC, although certainclinical trials have shown promising results. Tar-geted therapeutic strategies including small inter-fering RNA, topical or systemic rapamycin orsimvastatin have recently been developed, butthey cannot be offered on a regular basis (3–6).Many alternative treatments have previously beenapplied in this condition with variable and partialclinical response. These include: topical emol-lients, keratolytic agents, mechanical removal ofexcessive hyperkeratotic skin, avoidance of physi-cal activity, analgesia, and so forth (7). Among thesystemic agents for treatment of PC, oral retinoidtherapy represents the treatment of choice (8).

Epidermolysis bullosa simplex and PC arecongenital keratinopathies in which painful footblisters and callosities severely reduce patientquality of life. Since 2006, a handful of studieshave begun to report the efficacy of BTX-A intreating both conditions.

In 2010, a retrospective evaluation of 14patients with epidermolysis bullosa simplex and

PC showed a remarkable reduction in plantarblistering and pain after BTX injections (9–11).BTX inhibits eccrine sweat glands by blockingthe acetylcholine pathway, thus reducing hyper-hidrosis, maceration, and blistering of the fragileepidermis. But even patients with no overthyperhidrosis or blisters reported pain relief.This may be explained by a more direct effect ofBTX on nociceptive C-fibers inhibiting neuro-peptide release from the sensory nerve axons.Also, BTX can decrease the release of pain medi-ators including substance P, calcium generelatedpeptide and glutamate, and also inhibit the vaso-dilation induced by the silent nociceptors thatinitiate neurogenic inflammation. These mecha-nisms may explain the effect of BTX on tender-ness in both keratinopathies. Activation ofTRVP3 on keratinocytes leads to the release ofalgogenic and pruritogenic substances inducingcutaneous pain. However, no reports have beenfound to date regarding the effect of BTX-A inthese new receptors (12–15).

The technique applied was similar to treat-ment for axillary and palmar hyperhidrosis, butthe same outcome is achieved when concen-trating the entire dose directly below blistersand callosities. Mechanical removal of callositiesby curettage prior to intradermal injections ofBTX-A may play a role in pain reduction due toreduced friction. The optimal anaesthesiamethod may vary amongst different patients,but superficial sedation with spontaneous venti-lation was applied in our cases. The dose ofBTX-A each session ranged from 75 to 150 Uper foot. Table 1 shows improvement scoresand our results in comparison with those ofprevious studies. The mean effect lasted 6months in both patients, no side effects were

FIG. 2. Case 2 (A) Painful blisters and erosions on the back of the feet. (B) Improvement after BTX injections.

Efficacy of botulinum toxin in pachyonychia congenita type 1

3

reported and effectiveness was sustained overtime.

Conclusion

There is, thus far no curative treatment for PC,and agents previously used to treat this condi-tion have led to variable clinical outcomes. Untiltargeted therapeutic treatment can be offered ona routine clinical basis, our findings support theusefulness of BTX-A plantar injections in provid-ing sustained symptomatic relief to PC patientsand reducing painful foot blistering and callos-ities with good tolerance and lasting effects. Assuch, BTX-A treatment may offer a markedimprovement in the quality of life for patientsaffected by this rare and incapacitating disease.

Acknowledgements

The authors thank Savana Shakir and John Turcanyfor their participation.

Conflict of interests

None of the authors have any conflict of interestto declare.

References

1. Eliason MJ, Leachman SA, Feng BJ, Schwartz ME,

Hansen CD. A review of the clinical phenotype of 254

patients with genetically confirmed pachyonychia con-

genita. J Am Acad Dermatol 2012: 67 (4): 680–686.

2. Schnider P, Moraru E, Kittler H, et al. Treatment of focal

hyperhidrosis with botulinum toxin type A. long-term fol-

low-up in 61 patients. Br J Dermatol 2001: 145: 289–293.

3. Chamcheu JC, Wood GS, Siddiqui IA, et al. Progress

towards genetic and pharmacological therapies for kera-

tin genodermatoses: current perspective and future

promise. Exp Dermatol 2012: 21 (7): 481–489

4. Hickerson RP, Flores MA, Leake D, et al. Use of self-

delivery siRNAs to inhibit gene expression in an organo-

typic pachyonychia congenita model. J Invest Dermatol

2011: 131 (5): 1037–1044

5. Hickerson RP, Leake D, Pho LN, Leachman SA, Kaspar RL.

Rapamycin selectively inhibits expression of an inducible

keratin (K6a) in human keratinocytes and improves

Table 1. Global outcome and details of therapy comparing our results with those of previous studies

Our cases (n 5 2)

Swartlingand Vahlquist

2006 (9) (n 5 3)Swartling et al.2010 (11) (n 5 8)

Type of BTX A (Botox) A (Dysport) 7 A (Dysport),3 B (Neurobloc)*

Dose (U) ofBTX (range)

50 U (each palm)75–150 U (each foot)

125–300 U(each foot)

BTX-A: 200–350(each foot)BTX-B: 2500

Improve incallosities (average)†

1,5 u 2

Improve inblistering (average)†

3 u 1,6

Improve inpain (average)†

2 u 2,1

DLQI scorebefore/after treatment(average)‡

23 (before)/3 (after) u u

Effect duration(range and average)

5–6 months (5, 5) 6 weeks–6 months (3, 5)

2–12 months (3)

Number of treatments(range and average)

1–9 (5) u 1–19 (8)

Follow-up (months) Case 1: 60; case 2: 5 24 60Type of anaesthesia Superficial sedation IVRA§ 3 General, 5 IVRASide effects None None 3/8 mild¶

*Due to treatment resistance, three patients were later switched to BTX B (Neurobloc).†0, no effect; 1, a little better; 2, much better; 3, very much better.‡DLQI (Dermatology Life Quality Index): 0–1: no effect at all on patient’s life; 2–5: small effect on patient’s life; 6–10: moder-

ate effect on patient�s life; 11–20: very large effect on patient�s life; 21–30 extremely large effect on patient’s life.§IVRA: intravenous regional anaesthesia.¶Dysphagia in one case, and dry mouth, accommodation problems and urinary stress incontinence in two cases. n: number

of patients. u: unknown.

Gonz�alez-Ramos et al.

4

symptoms in pachyonychia congenita patients. J Dermatol

Sci 2009: 56 (2): 82–88.

6. Zhao Y, Gartner U, Smith FJ, McLean WH. Statins down-

regulate K6a promoter activity: a possible therapeutic

avenue for pachyonychia congenita. J Invest Dermatol

2011: 131 (5): 1045–1052

7. Goldberg I, Fruchter D, Meilick A, Schwartz ME, Sprecher

E. Best treatment practices for pachyonychia congenita.

J Eur Acad Dermatol Venereol 2014: 28 (3): 279–285.

8. Gruber R, Edlinger M, Kaspar RL, et al. An appraisal of

oral retinoids in the treatment of pachyonychia congen-

ita. J Am Acad Dermatol 2012: 66 (6): e193–e199

9. Swartling C, Vahlquist A. Treatment of pachyonychia

congenital with plantar injections of botulinum toxin. Br

J Dermatol 2006: 154: 763–765

10. Abitbol RJ, Zhou LH. Treatment of epidermolysis bullosa

simplex, Weber-Cockayne type, with botulinum toxin

type A. Arch Dermatol 2009: 145 (1): 13–15

11. Swartling C, Karlqvist M, Hymnelius K, Weis J, Vahlquist

A. Botulinum toxin in the treatment of sweat-worsened

foot problems in patients with epidermolysis bullosa

simplex and pachyonychia congenital. Br J Dermatol

2010: 163 (5): 1072–1076

12. Bentsianov B, Zalvan C, Blitzer A. Noncosmetic uses of

botulinum toxin. Clin Dermatol 2004: 22 (1): 82–88

13. Kr€amer HH, Angerer C, Erbguth F, Schmelz M, Birklein F.

Botulinum Toxin A reduces neurogenic flare but has

almost no effect on pain and hyperalgesia in human skin.

J Neurol 2003: 250 (2): 188–193.

14. Gazerani P, Pedersen NS, Staahl C, Drewes AM, Arendt-

Nielsen L. Subcutaneous botulinum toxin type A reduces

capsaicin-induced trigeminal pain and vasomotor reac-

tions in human skin. Pain 2009: 141 (1–2): 60–69.

15. Nilius B, B�ır�o T, Owsianik G. TRVP3: time to decipher a

poorly understood family member! J Physiol 2014: 592(Pt 2): 295–304

Efficacy of botulinum toxin in pachyonychia congenita type 1

5

ORIGINAL ARTICLE

An appraisal of oral retinoids in the treatmentof pachyonychia congenita

Robert Gruber, MD,a Michael Edlinger, MSc,b Roger L. Kaspar, PhD,c C. David Hansen, MD,d

Sancy Leachman, MD, PhD,d Leonard M. Milstone, MD,e Frances J. D. Smith, PhD,f Alexis Sidoroff, MD,a

Peter O. Fritsch, MD,a and Matthias Schmuth, MDa

Innsbruck, Austria; Santa Cruz, California; Salt Lake City, Utah; New Haven, Connecticut;

and Dundee, United Kingdom

From

M

br

m

D

an

Supp

Re

Conf

Background: Pachyonychia congenita (PC), a rare autosomal-dominant keratin disorder caused bymutations in keratin genes KRT6A/B, KRT16, or KRT17, is characterized by painful plantar keratodermaand hypertrophic nail dystrophy. Available studies assessing oral retinoid treatment for PC are limited to afew case reports.

Objective: We sought to assess overall effectiveness, adverse effects, and patient perspective in patientswith PC receiving oral retinoids.

Methods: In a questionnaire-based retrospective cross-sectional survey of 30 patient with PC assessing oralretinoids (10-50 mg/d for 1-240 months), we determined the clinical score, satisfaction score, visual analogpain scale, and adverse effects.

Results: In 50% of patients there was thinning of hyperkeratoses (average improvement 1.6 on a scalefrom e3 to 13) (95% confidence interval 1.2-1.9, P \ .001). In all, 14% observed amelioration of theirpachyonychia; 79% did not experience any nail change. The self-reported overall satisfaction score withoral retinoid treatment was 2 or greater in 50% of the patients (mean 4.5 on a scale of 1-10). Although 33%reported decreased and 27% increased plantar pain with treatment, 40% did not notice any pain change. Allpatients experienced adverse effects, and 83% reported to have discontinued medication. Risk/benefitanalysis favored lower retinoid doses (# 25 mg/d) over a longer time period ([5 months), compared withhigher doses ([25 mg/d) for a shorter time (# 5 months).

Limitations: The retrospective, cross-sectional study design is prone to a recall bias.

Conclusion: Oral retinoids are effective in some patients with PC. However, many patients discontinuedmedication because adverse effects outweighed the benefits. Careful dose titration is warranted in patientsinformed about potential adverse effects. ( J Am Acad Dermatol 10.1016/j.jaad.2011.02.003.)

Key words: keratins; keratoderma; oral retinoids; pachyonychia congenita.

Pachyonychia congenita (PC) (OnlineMendelian Inheritance in Man [OMIM]#167200 for PC-1, #167210 for PC-2) is a rare

autosomal-dominant ectodermal dysplasia that ischaracterized by hypertrophic nail dystrophy,

the Department of Dermatologya and Department of

edical Statistics, Informatics and Health Economics,b Inns-

uck Medical University; TransDerm Inc, Santa Cruzc; Depart-

ent of Dermatology, University of Utahd; Department of

ermatology, Yale University School of Medicine, New Havene;

d College of Life Science, University of Dundee.f

orted in part by the International Pachyonychia Congenita

search RegistryePachyonychia Congenita Project.

licts of interest: None declared.

extremely painful diffuse or focal symmetrical hy-perkeratosis of palms and soles sometimes associatedwith erosions, follicular keratosis on the extensorsurfaces of the extremities, oral leukokeratosis, andother ectodermal defects.1-3 At the molecular level,

Accepted for publication February 1, 2011.

Reprint requests: Matthias Schmuth, MD, Department of

Dermatology, Innsbruck Medical University, Anichstr. 35, 6020

Innsbruck, Austria. E-mail: [email protected].

Published online May 21, 2011.

0190-9622/$36.00

� 2011 by the American Academy of Dermatology, Inc.

doi:10.1016/j.jaad.2011.02.003

e1

http://dx.doi.org/10.1016/j.jaad.2011.02.003

mailto:[email protected]

http://dx.doi.org/10.1016/j.jaad.2011.02.003

J AM ACAD DERMATOLe2 Gruber et al

PC is caused by dominant-negative mutations inkeratin genes KRT6A, KRT6B, KRT16, andKRT17.4-6 As these keratins are expressed in differ-entiated epithelial structures such as the nail bed,palmoplantar epidermis, and the oral mucosa, theseare the affected tissues in PC-1.2,5 The hitherto com-mon division of PC into PC-1 and PC-2 subtypes

CAPSULE SUMMARY

d Available studies assessing oral retinoidtreatment for pachyonychia congenita(PC), a rare keratin disorder characterizedby painful plantar keratoderma and naildystrophy, are limited to a few casereports.

d Our study shows that althoughtreatment of PC with oral retinoids iseffective in some individuals with PC,increased pain is a common adverseeffect.

d The study presents the benefit/risk ratioof oral retinoids in PC and provides newinsight in favorable dosing regimens.

according to the clinical pre-sentation is being increas-ingly replaced withgenotype-inclusive nomen-clature (eg, PC-K6a, PC-K6b,PC-K16, and PC-K17).7

Treatment of PC is notori-ously difficult. Because PC israre (;1:500,000-1:1000,000),available studies assessingtherapeutic regimen are lim-ited to a few case reports andcase series. Basic measuresinclude topical emollients,keratolytic agents,mechanicalremoval of excessive hyper-keratotic skin, and avoidanceof physical activity. Amongthe systemic agents for treat-ment of PC, the best results
have been reportedwith oral administration of vitaminA derivatives, ie, retinoids.8-11 However, the evidencefor their effectiveness is based on anecdotal reportsand no systematic retrospective or prospective studiesare available. For severe inherited disorders of corni-fication such as ichthyoses and psoriasis, oral retinoidtherapy represents the treatment of choice.12,13 In PC,this therapeutic approach is particularly attractive,because in screening assays, retinoidshavebeennotedto suppress mutant keratin expression (W.H. IrwinMcLean, DSc, FRSE, oral communication, May 2010).We here present a questionnaire-based retrospectivecross-sectional survey of 30 patients assessing effec-tiveness, adverse effects, and overall patient satisfac-tion of oral retinoid therapy for PC. Our goal was toestablish the benefit/risk ratio, identify favorable dos-ing regimens, and determine if a future prospectivetrial for oral retinoid treatment of PC is justified.
METHODSPatients

All individuals presenting with PC with knownmutations in KRT6a, KRT16, or KRT17 whowere enrolled in the International PachyonychiaCongenita Research Registry between 2004 and2010 and previously treated with oral retinoids(acitretin, etretinate, isotretinoin, or vitamin A) atdifferent doses and durations (Table I) were

included in this questionnaire-based retrospec-tive cross-sectional study. The study was con-ducted in accordance with the principles of theDeclaration of Helsinki and written informedconsent was obtained from all 30 patients beforeenrollment.

QuestionnaireQuestionnaire-based pa-

tient scoring was used toevaluate clinical score, satis-faction score, visual analogpain scale, and adverse ef-fects of treatment with oralretinoids by self-assessment.Patients were either inter-viewed in person or via tele-phone. The questionnaireitems are summarized inTable II.

StatisticsAll data were analyzed

with software (SPSS, Version17.0 for Windows, SPSS Inc,Chicago, IL). Statistical differ-ences between groups were

determined by using the Mann-Whitney U test withsignificance conferred when P less than .05. Toassess predictors of the effectiveness of drug treat-ment we estimated odds ratios and 95% confidenceintervals (CIs) with logistic regression modeling; thisanalysis was restricted to the retinoids acitretin andisotretinoin given the small number of cases on otherretinoids.

RESULTSNatural course of plantar hyperkeratoses in PC

As PC is a dynamic disease, 25 of the 30 patients(83%) (Table I) who received oral retinoids reportedspontaneous changes in plantar hyperkeratoseswhile not using any medication. On a scale of e3(much worse) to 13 (much better) plantar thicken-ing was reported to range between e1.8 and 0.9,with an average change of e0.45, ie, the majority ofpatients reported worsening of the disease while nottaking any drugs. These results indicate that withoutmedication plantar hyperkeratoses in PC varies overtime with little spontaneous improvement.

Treatment effectivenessFifteen patients (50%) reported decreased plantar

hyperkeratoses, ie, thinning of calluses, when takingmedication (Fig 1). On a scale frome3 (muchworse)to 13 (complete improvement) the average

Table I. Patient demographics and retinoid therapy

No. Gene Mutation Sex Retinoid Dose, mg/d Duration, mo

1 K6a D432_E470dup F Isotretinoin NA 12 K16 N125D M Isotretinoin 25 243 K6a N172del M Etretinate 50 64 K16 L132P F Acitretin NA 65 K6a N171K F Isotretinoin NA 36 K17 N92S F Isotretinoin 50 37 K16 L132P F Etretinate 12,5 2408 K16 L132P F Acitretin 50 129 K6a L468P F Acitretin 10 2410 K6a L469R F Isotretinoin NA 611 K16 L132P M Acitretin NA 1212 K6a N171Y M Acitretin 25 6013 K16 S130del M Isotretinoin 40 114 K17 N92S F Isotretinoin 40 615 K16 L132P F Isotretinoin 40 616 K6a N172del F Acitretin 25 417 K6a E461K M Isotretinoin NA 318 K16 K15X F Isotretinoin NA 319 K17 M88T F Isotretinoin 40 920 K17 M88T M Acitretin 25 2421 K17 N92S M Isotretinoin NA 322 K16 L124H F Acitretin 30 323 K16 N125S M Acitretin 25 324 K6a L468P F Isotretinoin 40 625 K17 N92S F Isotretinoin NA 226 K16 L132P M Acitretin 25 527 K16 N125S M Acitretin 20 428 K6a N172del M Etretinate 10 229 K6a N172del M Acitretin 25 1230 K16 L132P F Ro-A-Vit 50 1

F, Female; M, male; NA, not applicable.

J AM ACAD DERMATOL Gruber et al e3

improvement was 1.6 (95% CI 1.2-1.9, P \ .001).Although 4 of the 28 patients (14%) for whomdata onnail thickening were available reported ameliorationof their pachyonychia (thinning of nails, lightercolor) with an average improvement of 1.5 on ascale from e3 to 13, the majority of the individuals,ie, 22 (79%), did not experience any change in nailinvolvement and only two patients (7%) reportedworsening of their pachyonychia. The self-reportedoverall satisfaction score with oral retinoid treatmentwas greater than or equal to 2 in 15 patients (50%),with a mean of 4.5 on a scale of 1 (lowest) to 10(highest). Notably, only 7 patients (23%) recommendthe use of oral retinoids to others and even fewer, 5patients (17%), are still using the medication.

Effects on painBefore treatment with oral retinoids, the overall

pain when walking was quantified by a visual analogpain scale (0 meaning no pain and 10 the worst painever experienced) and reported as 6, which signified

dreadful pain. Decreased plantar pain during ther-apy was reported in 10 patients (33%) whereas8 patients (27%) experienced increased pain andthe remaining 12 patients (40%) did not report anychange in their pain.

In the majority of individuals with decreased pain,the improvement occurred within the first 3 to 4weeks of taking oral retinoids. In the 10 patients withdecreased plantar pain, the degree of pain amelio-ration ranged from 1 to 7 on a scale of 1 (minimal) to10 (most), with a mean change of 3.4 (95% CI 1.8-5.1,P = .001). In the 8 patients who experienced in-creased pain, the degree of pain worsening rangedfrom 3 to 10, with a mean change of 7.1 (95% CI5.4-8.8, P\ .001).

Retinoid dosingAmong the participants of this study taking oral

retinoids the dose ranged from 10 to 50 mg/d(Table I). Forty percent of patients who were treatedwith doses of more than 25 mg/d (higher doses),

Table II. Questionnaire

Natural course of PC without treatmentd Did your PC condition change at times when not using any drug treatment?d If yes, indicate range of change on scale of e3 (much worse) to 13 (much better), with 0 being your normal condition

Effectiveness/satisfactiond Was drug effective?d What was your overall satisfaction on scale of 1-10 (1 = lowest, 10 = highest)?d Are you still using drug?d Would you recommend drug to others?

Clinical treatment responsed While taking drug did your PC calluses/nails change?d If yes, did calluses/nails get better or worse?d If calluses/nails got better, what was improvement?d What was clinical improvement/deterioration in your PC calluses/nails on scale of e3 (much worse) to 13 (completeimprovement)?

Paind On scale of 0 (no pain) to 10 (worst pain you have ever experienced), rate your overall pain before taking drugd While on drug, did you notice change in pain?d If yes, did change cause more/less pain?d If yes, indicate when change occurredd If yes, mark change in your pain using scale of 1 (minimal) to 10 (most)

Dose and durationd Which oral retinoid did you use (trade name)?d If you remember, what dose or strength of medication did you use?d How long did you take this medication?d Was dose of your retinoid medication changed during treatment?d If yes, to higher/lower dose?d If yes, why was dose changed?d Did change give more improvement?d Did change create more adverse effects?

Adverse effectsd Did you experience any adverse effects?d Did you experience any dry eyes/dry lips/dry skin/peeling of skin/hair loss/headaches/bone or joint pain/other adverseeffects while taking drug?

d Did your doctor find any liver problems caused by use of retinoid treatment?d Did you think improvement you experienced while taking drug was sufficient that you wanted to continue in spite of anyadverse effects?

d Based on your experience, would you be interested in using oral retinoids again?

PC, Pachyonychia congenita.


reported overall effectiveness and a mean overallsatisfaction score of 1.6 on a scale from 1 (lowest) to10 (highest). In comparison, 73% of patients receiv-ing oral retinoid doses of less than or equal to25 mg/d (lower doses) reported overall effectiveness(P = .14) and a mean overall satisfaction score of4.2 on a scale from 1 to 10 (P = .02). These resultssuggest that although lower doses are not signifi-cantly different in their effectiveness, the ratiosamong effectiveness, pain, and adverse effectswere more favorable with lower doses. Decreasedplantar pain during therapy with oral retinoids wasreported in 50% treated with higher doses and 67% ofpatients treated with lower doses (P = .53), ie, higherretinoid doses were not superior in reducing pain.

Treatment durationThe duration of treatment with oral retinoids

ranged from 1 to 240 months, with 50% of thepatients receiving therapy for longer than 5 months(longer duration) and 50% less than or equal to 5months (shorter duration) (Table I). Of patients whowere treated for a longer duration, 67% reportedoverall effectiveness and a mean overall satisfactionscore of 3.6 on a scale from 1 to 10 compared with33% effectiveness (P = .07) and a score of 1.9 (P = .06)in the patients receiving oral retinoids for a shorterduration. An improvement of PC calluses wasreported in 83% of patients treated longer than5 months and 75% treated for 5 months or less (P =.66); the overall change in plantar hyperkeratosis on

Fig 1. A, Thick plantar hyperkeratosis in patient with pachyonychia congenita beforetreatment with oral retinoids. B, Thinning of calluses while on therapy with acitretin. However,medication had to be discontinued because of adverse effects, ie, peeling of skin and increasedpain and vulnerability of feet when walking.


a scale from e3 (much worse) to 13 (completeimprovement) was 0.7 for the longer duration groupversus 0.3 for the shorter duration group (P = .38).A decrease in plantar pain was reported in 67% ofpatients treated for a longer period and 33% treatedfor a shorter duration, but this again was not statis-tically different (P = .19). Interestingly, the percent-age of patients with increased plantar pain was lowerin the group with longer treatment duration (33%vs 67%).

Retinoid classesOnly patients who had received acitretin (N = 12)

or isotretinoin (N = 14) were further comparedbecause of the small number of patients treatedwith etretinate or vitamin A (Table I). The overalleffectiveness was 58% for acitretin and 36% forisotretinoin (P = .26), the overall satisfaction scorewas 3.5 for acitretin versus 2.1 for isotretinoin (P =.14). Ninety percent of patients in the acitretingroup compared with 57% in the isotretinoin groupreported thinning of calluses (P = .13) (Fig 1); theoverall change on a scale from e3 (much worse) to13 (complete improvement) was 0.9 versus e0.1(P = .05). In all, 63% versus 50% experienceddecreased plantar pain while on acitretin andisotretinoin, respectively (P = .65). Although notsignificantly different, these data indicate that aci-tretin may have a slight edge over isotretinoin intreating PC.

Adverse effectsAll study patients experienced adverse effects.

With the exception of one man all patients reporteddry lips, 15 (50%) dry eyes, 27 (90%) dry skin, 11(37%) peeling of the skin, 9 (30%) hair loss, 6 (20%)headaches, 5 (17%) bone or joint pain, 4 (13%) sunsensitivity, and one patient depression, fatigue, anddeveloping of bone spurs, respectively. In one pa-tient treatment with oral retinoids was stoppedbecause of liver enzyme abnormalities.

Considering retinoid doses, ie, more than25 mg/d versus less than or equal to 25 mg/d, theprevalence of adverse effects such as dry lips (90% vs100%, P = .29), dry eyes (20% vs 64%, P = .05), dryskin (90% vs 91%, P = .94), skin peeling (50% vs 36%,P = .54), hair loss (20% vs 55%, P = .11), headaches(20% vs 18%, P = .92), and bone/joint pain (20% vs36%, P = .42) was comparable. There was nodifference in adverse effects relative to treatmentduration and there was also no significant differencein adverse effects when comparing acitretin withisotretinoin.

Nine patients (30%) decided to continue treat-ment with oral retinoids despite adverse effectsbecause they perceived PC improvement as suffi-cient. Based on their experience, 14 patients (47%)would be interested in using oral retinoids again,primarily because of the overall effectiveness theyexperienced. Sixteen patients (53%) would not useoral retinoids again. However, the question used forthis assessment (Table II) did not address in detail


why patients stated that they would or would notwant to use oral retinoids again.

Predictors of effectivenessTo identify additional patient subsets thatmight be

more likely to benefit from oral retinoid treatment,we used logistic regression modeling. The calculatedodds ratios were 0.13 for female versus male (95% CI0.02-0.89), 1.6 for acitretin versus isotretinoin (95%CI0.3-9.6), and 0.7 for age, per 10 years (95% CI 0.4-1.5). These results indicate that neither patient agenor retinoid type were predictors of effectiveness. Incontrast, a benefit from oral retinoid treatment wasless likely in female than in male patients.

DISCUSSIONThe few available case reports and case series

assessing therapy of PC with oral retinoids yieldedcontradictory results with a tendency toward morefavorable outcomes with treatment. Dupr�e et al8

asserted improvement of PC calluses and decreasedpain in 3 patients treated with an aromatic retinoid,Hoting andWassilew9 reported a remission of palmo-plantar hyperkeratosis but no changes in pachyo-nychia in two patients treated with etretinate 75mg/dand a relapsewhen reducing thedrug to 30mg/d afterseveral months, Carabott et al10 described a patientwho experienced reduced plantar hyperkeratosisafter 3 months of etretinate therapy at a dose of50 mg/d, and Lim et al11 reported amelioration ofcalluses but not of nail changes in a patient treatedwith 30 mg acitretin daily. In contrast, two additionalcase reports did not show any clinical benefit for oralretinoids in the treatment of PC. Thomas et al14

reported a father and his son who did not showimprovement of plantar keratoderma despite therapywith high doses of isotretinoin. Similarly, Soyuer andCandan15 described failure of etretinate in a childwith PC, but the treatmentwasonly administered for 5weeks, and the dose had to be progressively loweredbecause of hypertriglyceridemia. Consistent with thecontradictory findings in these published reports,in the current study involving 30 patients from thePC registry, oral retinoids resulted in thinning ofcalluses (decrease in hyperkeratosis) in only a subsetof study patients.

A very important aspect of PC treatment is thatthinning of calluses does not necessarily imply de-creased plantar pain when walking, as reported forother types of palmoplantar keratoderma. In a familywith keratoderma of the soles associated with blis-tering but lack of pachyonychia, treatment withisotretinoin resulted in callus reduction, but blister-ing worsened and pain increased.16 This was alsoobserved by Fritsch et al,17 who described a dramatic

improvement of hereditary epidermolytic palmo-plantar keratoderma in 4 patients treated with anoral aromatic retinoid for 5 months, resulting innormal-appearing skin. However, therapy had to bediscontinued as the vulnerability and sensitivityrestricted normal function of hands and feet. In thecurrent study roughly only one third of patientsexperienced improvement of pain although 50% ofthe patients reported improved plantar hyperkera-tosis, ie, in some cases even though calluses thinned,there was increased pain.

Recently, mutations in KRT6, KRT16, and KRT17were correlated with characteristic clinical findingsin patients with PC; ie, KRT6B was associated withincreased pain intensity.18 When stratifying our pa-tients by genotypes, because of the small subgroups,no further analysis regarding treatment effectivenesswas possible.

This study has several limitations including itsretrospective, cross-sectional study design, which isprone to a recall bias. Although the measurementswere patient-based and subjective, ie, not assessedby a physician, the study end points are patient-centered in a positive sense, in that they should behighly relevant for reflecting patient perception oftreatment. The lack of laboratory monitoring forpotential adverse effects such as liver function testingmay result in an overestimation of the benefit/riskratio of the treatment modality, ie, our study design isbiased to exclude patients with severe adverseeffects. In the current study, discontinuation of oralretinoid therapy was only necessary in one patientbecause of elevated liver transaminases. This is inaccordance with two previous studies, in whichsimilar retinoid doses have been used for the treat-ment of various forms of ichthyoses and psoriasis,and no severe adverse effects were reported.12,13

This study demonstrates a potential advantage oftreatment with lower doses of acitretin for a longerduration compared with therapy with higher doses,shorter duration, and isotretinoin. Recently it wasshown that in the treatment of patients with psoriasislow-dose acitretin (25 mg/d) was associated withfewer common adverse effects than high-dose aci-tretin (50 mg/d).13 Because lower doses may havea better risk/benefit ratio, it might be beneficialto begin treatment at a lower dose (eg, acitretin10-25 mg/d) with further dose adjustments based onpatient’s response. Alternatively, treatment may beinitiated at a higher dose and subsequently adjusteddepending on pain and adverse effects. It is impor-tant that patients are fully informed about potentialadverse effects before initiation of therapy includingthe possibility of increased pain when on oralretinoids.


In conclusion, the results of our study confirm thattreatment of PC with oral retinoids is effective insome individuals with PC. Randomized, controlled,prospective clinical trials with both objective andpatient-centered subjective end points are warrantedto further define the patient subsets that most benefitfrom this treatment option.

We are indebted to the participating patients, andto Mary Schwartz and the members of the PC ProjectMedical Scientific Advisory Board for their valuableadvice.

REFERENCES

1. Feinstein A, Friedman J, Schewach-Millet M. Pachyonychia

congenita. J Am Acad Dermatol 1988;19:705-11.

2. Leachman SA, Kaspar RL, Fleckman P, Florell SR, Smith FJ,

McLean WH, et al. Clinical and pathological features of

pachyonychia congenita. J Investig Dermatol Symp Proc

2005;10:3-17.

3. Jackson AD, Lawler SD. Pachyonychia congenita; a report of

six cases in one family, with a note on linkage data. Ann Eugen

1951;16:142-6.

4. Smith FJ, Jonkman MF, van Goor H, Coleman CM, Covello SP,

Uitto J, et al. A mutation in human keratin K6b produces a

phenocopy of the K17 disorder pachyonychia congenita type

2. Hum Mol Genet 1998;7:1143-8.

5. McLean WH, Rugg EL, Lunny DP, Morley SM, Lane EB,

Swensson O, et al. Keratin 16 and keratin 17 mutations cause


6. Bowden PE, Haley JL, Kansky A, Rothnagel JA, Jones DO,

Turner RJ. Mutation of a type II keratin gene (K6a) in


7. Eliason MJ. A review of the clinical phenotype in patients with

pachyonychia congenita. Submitted for publication.

8. Dupr�e A, Christol B, Bonafe JL, Touron P. Pachyonychia con-

genita: three familial cases; effects of the treatment by aromatic

retinoid (RO 10.9359). Ann Dermatol Venereol 1981;108:145-9.

9. Hoting E, Wassilew SW. Systemic retinoid therapy with etret-

inate in pachyonychia congenita [in German]. Hautarzt 1985;

36:526-8.

10. Carabott F, Archer CB, Griffiths WA. Etretinate-responsive

pachyonychia congenita. Br J Dermatol 1988;119:551-3.

11. Lim TW, Paik JH, Kim NI. A case of pachyonychia congenita

with oral leukoplakia and steatocystoma multiplex. J Dermatol

1999;26:677-81.

12. Verfaille CJ, Vanhoutte FP, Blanchet-Bardon C, van Steensel

MA, Steijlen PM. Oral liarozole vs acitretin in the treatment of

ichthyosis: a phase II/III multicenter, double-blind, random-

ized, active-controlled study. Br J Dermatol 2007;156:965-73.

13. Pearce DJ, Klinger S, Ziel KK, Murad EJ, Rowell R, Feldman SR.

Low-dose acitretin is associated with fewer adverse events

than high-dose acitretin in the treatment of psoriasis. Arch

Dermatol 2006;142:1000-4.

14. Thomas DR, Jorizzo JL, Brysk MM, Tschen JA, Miller J, Tschen

EH. Pachyonychia congenita: electron microscopic and epi-

dermal glycoprotein assessment before and during isotreti-

noin treatment. Arch Dermatol 1984;120:1475-9.

15. Soyuer U, Candan MF. Failure of etretinate therapy in pach-

yonychia congenita. Br J Dermatol 1987;117:264.

16. Baden HP, Bronstein BR, Rand RE. Hereditary callosities with

blisters: report of a family and review. J Am Acad Dermatol

1984;11:409-15.

17. Fritsch P, Honigsmann H, Jaschke E. Epidermolytic hereditary

palmoplantar keratoderma: report of a family and treatment

with an oral aromatic retinoid. Br J Dermatol 1978;99:561-8.

18. Eliason MJ. IPCRR Data 2010. Paper presented at: International

PC Consortium Symposium; May 2010, Atlanta, GA.

original article© The American Society of Gene & Cell Therapy

Molecular Therapy 1

The rare skin disorder pachyonychia congenita (PC) is an autosomal dominant syndrome that includes a dis-abling plantar keratoderma for which no satisfactory treatment is currently available. We have completed a phase Ib clinical trial for treatment of PC utilizing the first short-interfering RNA (siRNA)-based therapeutic for skin. This siRNA, called TD101, specifically and potently tar-gets the keratin 6a (K6a) N171K mutant mRNA without affecting wild-type K6a mRNA. The safety and efficacy of TD101 was tested in a single-patient 17-week, prospec-tive, double-blind, split-body, vehicle-controlled, dose-escalation trial. Randomly assigned solutions of TD101 or vehicle control were injected in symmetric plantar calluses on opposite feet. No adverse events occurred during the trial or in the 3-month washout period. Sub-jective patient assessment and physician clinical efficacy measures revealed regression of callus on the siRNA-treated, but not on the vehicle-treated foot. This trial represents the first time that siRNA has been used in a clinical setting to target a mutant gene or a genetic dis-order, and the first use of siRNA in human skin. The cal-lus regression seen on the patient’s siRNA-treated foot appears sufficiently promising to warrant additional studies of siRNA in this and other dominant-negative skin diseases.

Received 19 June 2009; accepted 19 October 2009; advance online publication 24 November 2009. doi:10.1038/mt.2009.273

IntroductIonThe emergence of short-interfering RNA (siRNA) as a powerful tool to reduce target gene expression in vitro and in animal model systems has led to recent therapeutic trials of siRNAs for macular degeneration, diabetic macular edema, solid tumors, respiratory syncytial virus, hepatitis B, and human immunodeficiency viral infections.1–5 However, these trials have not yet been published. To date, the only published clinical trial reporting the use of a siRNA is a safety and tolerability study for respiratory syncytial

virus.6 This phase I siRNA trial for respiratory syncytial virus demonstrated few side effects and promising signs of efficacy. The siRNA trial reported herein is the first-in-man siRNA trial for a skin disorder as well as the first to target a mutated gene causing an inherited disease.

Pachyonychia congenita (PC) is an ultrarare (less than a few thousand cases worldwide7), highly disabling, autosomal domi-nant inherited disorder that affects the nails, skin, oral mucosae, hair, and teeth.8,9 Manifestations are regionally variable but focally persistent and do not spontaneously resolve. The most disabling feature of PC is painful plantar calluses for which no satisfactory treatment is currently available. Although PC symptoms and pain levels vary between patients, many are unable to walk without the aid of crutches at least intermittently or must use a wheelchair. PC patients often walk on their knees while at home to avoid contact with the plantar calluses. Although it is not possible to effectively or safely remove PC calluses completely, patients routinely use pumice stones and razor blades to groom the calluses to help alleviate pain. These calluses are so exquisitely sensitive that patients rarely allow others, even family members, to touch their feet. PC patients could benefit enormously from an effective, locally administered therapy.

PC is caused by mutations in either keratin K6, K16, or K17 that act by a dominant-negative mechanism to cause the disease symptoms.8,9 Selective depletion of the mutated keratin has the potential to directly target the molecular etiology of the disease, and there is compelling evidence from animal models, at least in the case of a similar keratin disorder, epidermolysis bullosa simplex (due to keratin 14), that even partial reduction of mutant keratin expression may have a beneficial clinical effect.10 Further, substan-tial redundancy among PC-related keratins, as demonstrated in knockout mice,11 reduces the likelihood of a severe adverse event if a single keratin is eliminated (e.g., if both wild-type and mutant keratin 6a (K6a) were inhibited by the siRNA). Overall, the focal nature of PC, our understanding of the underlying molecular defects of the disorder, the lack of effective PC therapies, and the ability to visually observe changes during treatment make PC a particularly good human skin disease model for testing siRNA in a proof-of-concept trial for genetic disorders.

Correspondence: Sancy A Leachman, Huntsman Cancer Institute, Department of Dermatology, 2000 Circle of Hope, Salt Lake City, Utah 84112-5550, USA. E-mail: [email protected]

First-in-human Mutation-targeted siRNA Phase Ib Trial of an Inherited Skin DisorderSancy A Leachman1, Robyn P Hickerson2, Mary E Schwartz3, Emily E Bullough1, Stephen L Hutcherson4, Kenneth M Boucher1, C David Hansen1, Mark J Eliason1, G Susan Srivatsa5, Douglas J Kornbrust6, Frances JD Smith7, WH Irwin McLean7, Leonard M Milstone8 and Roger L Kaspar2

1Department of Dermatology Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA; 2TransDerm Inc., Santa Cruz, California, USA; 3PC Project, Salt Lake City, Utah, USA; 4Visionary Therapeutics Corporation, Richmond, Virginia, USA; 5ElixinPharma, Encinitas, California, USA; 6Preclin-sight, Reno, Nevada, USA; 7Division of Molecular Medicine, Medical Sciences Institute, University of Dundee, Dundee, UK; 8Department of Dermatology, Yale University, New Haven, Connecticut, USA

3http://www.nature.com/doifinder/10.1038/mt.2009.273


2 www.moleculartherapy.org

© The American Society of Gene & Cell TherapysiRNA Phase Ib Trial of an Inherited Skin Disorder

Preclinical studies have demonstrated that the TD101 siRNA is safe, as well as highly potent and specific.12,13 This siRNA has been shown to specifically target the cytosine-to-adenine single nucleotide K6a mutation (resulting in the amino-acid change N171K) in patient-derived immortalized keratinocytes.13 It has also been shown to reverse the mutant phenotype of cells in a dominant-negative tissue culture model by restoring their abil-ity to form a structurally intact keratin intermediate filament network.12,13 Furthermore, the TD101 siRNA has been tested in a mouse model using bicistronic reporter constructs consisting of firefly luciferase linked to either wild-type or N171K mutant K6a. Co-delivery of these constructs and the mutation-specific siRNA resulted in potent inhibition of the mutant (but not the wild-type) version of the gene, as assayed by in vivo biolumi-nescence imaging12 (and unpublished results). In a compari-son of unmodified and modified siRNA, we found that some modifications eliminated the single nucleotide specificity, and no increase in efficacy was observed using modified ver-sions (data not shown). Furthermore, we reasoned that if any unmodified siRNA were to enter the bloodstream, it would be quickly degraded, increasing the safety profile. For these rea-sons, unmodified TD101 was used in this trial. A mouse toxicity study demonstrated a lack of serious toxicity when the TD101 siRNA was delivered at high-dose levels by intradermal injec-tion.13 Thus, preclinical studies in in vitro and in vivo model systems demonstrated both safety and effective inhibition of N171K K6a by the TD101 siRNA.

The clinical efficacy and safety of TD101, administered by intralesional injection into a plantar callus, was evaluated in a single patient using a prospective, double-blind, split-body, vehicle-controlled, dose-escalation study design. Treatment was completed after 17 weeks of twice-weekly injections and was followed by a 3-month washout period (see Table 1 for dosing

schedule). Efficacy and safety measurements are detailed in the Materials and Methods section, as well as the Supplementary Materials and Methods.

resultsAt the conclusion of the washout period, the blinding code was broken and revealed that the right foot had received TD101 siRNA, whereas the left foot had received the vehicle-control solu-tion. Both subjective patient data and physician-derived clinical data suggest that in similar symmetric calluses, there was a posi-tive effect of the injection of TD101 in the right foot, but not in the vehicle control–injected left foot.

During the first 2 months of the trial, no dramatic differences (subjective or objective) between feet were noted by either the patient or physician. At this point in the trial, there were no visible responses in the calluses of either foot that would indicate either significant injury or efficacy from the drug. At approximately day 70 of the trial (dose = 2 ml; 3 mg/ml), the patient’s subjective eval-uation of the injected callus (“If you are receiving a study medica-tion, evaluate if it is working and improving your PC symptoms.” 0 = definitely working; 10 = definitely not working) began to indi-cate a marked difference in the right foot, but no change in the left foot (Figure 1). Measurements of the injected calluses also began to show a statistically significant decrease in length of the callus on the right foot only (Figure 2). On day 98 of the trial, after dose 28 (dose = 2 ml; 5.0 mg/ml), the callus at the site of injection on the right foot began to fall away and revealed healthy, pink skin. The underlying skin was remarkably nontender to palpation, whereas surrounding areas of callus retained sensitivity (Figure 3a). This type of behavior had never been observed by the patient previously (Figure 1 and patient personal communication). This reduction in tenderness is the most dramatic clinical observation in the trial. By day 115, not only was the reduced length of the callus obvious,

table 1 dose-escalation schedule

Week dose no. days Volume (ml)concentration of td101 (mg/ml)

total dose td101 (mg)

1 1–2 1–7 0.1 1.0 0.10

2 3–4 8–14 0.25 1.0 0.25

3 5–6 15–21 0.50 1.0 0.50

4 7–8 22–28 1.0 1.0 1.0

5 9–10 29–35 1.5 1.0 1.5

6 11–12 36–42 2.0 1.0 2.0

7 13–14 43–49 2.0 1.5 3.0

8 15–16 50–56 2.0 2.0 4.0

9 17–18 57–63 2.0 2.5 5.0

10 19–20 64–70 2.0 3.0 6.0

11 21–22 71–77 2.0 3.5 7.0

12 23–24 78–84 2.0 4.0 8.0

13 25–26 85–91 2.0 4.5 9.0

14 27–28 92–98 2.0 5.0 10.0

15 29–30 99–105 2.0 6.0 12.0

16 31–32 106–112 2.0 7.0 14.0

17 33 113–119 2.0 8.5 17.0

Molecular Therapy 3


but there was also an area clinically free of hyperkeratosis in the center of the injection site (Figure 3a). Subjective and objective changes in the right foot began returning toward baseline after the drug was discontinued and reached baseline ~30–50 days after the last dose. Figure 2 shows that the trend to shortening of the cal-lus length occurred prior to day 98 when the callus began peeling away from the injection site.

Because of the dynamic nature of callus development and res-olution, it is unclear at what dose the callus first began to regress. The cellular turnover and retention in PC calluses have never been measured, so it is difficult to surmise whether the lower doses of TD101 began to have a cumulative effect that was not observed until later or if the response at later time-points was due to an increased dose at that time. Future investigation with a single-dose level over a prolonged period of time may help to address these questions.

There were no clinical signs of a systemic response to the TD101 injections (i.e., outside the injection site) in the skin, nails, or oral mucosa of the patient. Not unexpectedly (given the small treatment area), the patient reported no significant changes in overall quality of life during the treatment period (P = 0.16). There were no clinical signs of local or systemic toxicity at intral-esional doses up to and including the highest TD101 dose admin-istered (17 mg). Similarly, no laboratory values suggested toxicity (Supplementary Tables S1–S4).

dIscussIonOn the basis of preclinical testing, and the dramatic and specific response of the patient’s treated callus to TD101, we have every reason to believe, but cannot prove, that the mechanism of the clinical effect was through RNA interference. We were unable to

obtain biopsy tissue for measurement of allele- specific mRNA levels because the protocol required repeated local adminis-tration of drug, and the safety evaluation arm of our protocol might have been compromised by repeated biopsies of the foot in an individual prone to blisters and infection. Recent data from animal studies of a siRNA for macular degeneration sug-gest that some of the clinical response may be a nonspecific reaction to the siRNA.14 Once an animal model of PC is avail-able, scrambled siRNAs and tissue biopsies will be important mechanistic controls for future studies. However, there is no evidence from our preclinical studies, where nonspecific siRNA controls were used at every stage, that TD101 is acting in a non-specific manner unrelated to selective degradation of mutant K6a mRNA.12,13,15

The degree of pain experienced by the patient at the time of injection is a significant concern. Although pain related to the injection did not persist longer than a few hours after injection, the intense pain experienced at the time of injection will limit the utility of the drug by this delivery method. At the incep-tion of this trial, the intradermal delivery route was selected to maximize the probability of observing an effect based on pre-clinical studies demonstrating reduced reporter gene expres-sion after intradermal injection of specific siRNA in mice.15,16 Future efforts must focus on improved delivery methods for TD101, such as pharmaceutical formulations for noninvasive topical delivery.

Despite our understanding of the molecular basis of PC,17 cur-rent treatment is limited to mechanical removal of thick calluses, nonspecific topical keratolytics and oral retinoids, none of which alleviates blistering or plantar pain satisfactorily.8 We believe the callus regression in this single-patient clinical trial of siRNA in PC is sufficiently promising to warrant additional studies of siRNA in this and other dominant-negative skin diseases.

Study day

Impr

ovem

ent s

core

Dos

e (m

g)

−50

2

4

6

8

10

0

5

10

15

20

0 50 100 150 200

VehicleTD101Dose

Figure 1 Patient assessment demonstrates subjective improvement in the right foot (td101, blue) but not the left foot (vehicle, red) as determined by daily diary entries. Note that the scores for the left foot have been slightly offset so that the left and right foot scores do not overlap at baseline. The improvement scores and a curve fit through the scores are both plotted. The corresponding dose (gray) is indicated by a separate graph. An improvement score of 10 represents “definitely not working,” whereas a score of 0 represents “definitely working.” The improvement returns to baseline after treatment is completed.

Dos

e (m

g)

0

5

10

15

20

Study day

Cal

lus

leng

th (

nm)

−50 0 50

70

80

90

100

110

100 150 200

VehicleTD101Dose

Figure 2 the length of the callus on the right foot (td101, blue), but not the left foot (vehicle, red), decreased significantly during the dosing period (day 0 to day 118) (drug versus vehicle, P = 0.004). The measured callus length (dots and open circles) and a piecewise lin-ear fit through the callus lengths are both plotted (see Materials and Methods). The fit has a change in slope at the end of the dosing period. The corresponding dose is indicated by a separate graph.

4 www.moleculartherapy.org


MaterIals and MethodsPatient enrollment and study design. After providing informed con-sent, an adult participant with PC carrying a KRT6A N171K mutation was enrolled in the phase Ib trial according to a protocol approved by the University of Utah Institutional Review Board and the Food and Drug Administration (IRB no. 24013 and IND no. 77504; ClinicalTrials.gov reg-istration no. NCT00716014; GMP (Good Manufacturing Practice) drug manufactured by Agilent Technologies, Santa Clara, CA). The patient was a 39-year-old female with no history of medical problems other than her PC symptoms. The patient served as her own control, with randomization of TD101 or vehicle control for intradermal injection to symmetric cal-luses on opposite feet. The test agents were packaged and labeled accord-ing to a computer-generated randomization list that assigned vehicle control or drug to the left or right foot. The decoded list of test agents was held in a secure place and not made available to the Principal Investigator, patient, or other study personnel until the conclusion of the trial.

The study evaluated safety and tolerance of multiple injections of escalating doses of TD101. Intradermal injections were given twice

weekly over 17 consecutive weeks for a total of 33 injections in each foot (Table 1). Two symmetric calluses were selected for treatment—one on each foot. Test agent or vehicle-control solution was injected as indicated by the randomization list. The central region of each callus was marked and injected at the same site for each treatment; other locations on the calluses were never treated. The injection was performed using a 30-gauge needle, inserted with a single needle-stick to penetrate to the level of the superficial dermis. This depth of injection was determined by the dramatic decrease in resistance that occurred in the subepidermis. The 2 ml injections produced ~2 cm subepidermal blisters, which corresponds to the central region of response on the treated callus (Figure 3a).

Beginning on day 29, in response to intense injection-related pain, the patient was premedicated with 2.5 mg diazepam and 5.0/325 mg hydrocodone/acetaminophen prior to each treatment. In addition, beginning on day 32, the patient also received bilateral posterior tibial nerve blocks with 2% preservative-free lidocaine. The treatment sites were each evaluated for adverse reactions before injections.

TD101 was administered on a volume and dose-escalation schedule (Table 1). The optimal dosing schedule for unmodified siRNA in skin is not known. We based the frequency of our dosing on the stability of TD101 siRNA in skin as demonstrated in our preclinical studies.15 We designed our treatment protocol to spread the injections out over a time period to optimize response and minimize the burden on the subject given the significant pain experienced by the subject during each injection. Initially, 0.1 ml of a 1.0 mg/ml solution of TD101 or vehicle alone (Dulbecco’s phosphate-buffered saline without calcium or magnesium) was administered to symmetric calluses. Six rising dose-volumes were completed without an adverse reaction to the increases: 0.1, 0.25, 0.5, 1.0, 1.5, and 2.0 ml of a 1.0 mg/ml solution of TD101 solution per injection. As the highest planned volume (2.0 ml) was well tolerated, the concentration of TD101 was then increased each week from 1 mg/ml up to a final concentration of 8.5 mg/ml. The pH of the placebo and stock study drug (10 mg/ml) was identical (7.0); furthermore, saline dilutions of up to 40-fold had no effect on pH (data not shown). The patient was followed for 3 months after the final injection, at which point the study was unblinded to both the patient and the Principal Investigator.

Study end points for safety. The maximum tolerated volume and the maximum tolerated dose were defined on the basis of the patient having a grade 2 or higher injection site reaction (erosion, unacceptable pain, or ulceration), or any adverse experience reported by the patient that resulted in discontinuation of the study (see Supplementary Materials and Methods for details regarding clinical safety definitions). Safety evalu-ations included assessments of adverse experiences by targeted clinical examination and clinical laboratory analyses. Clinical laboratory tests for safety were performed before first dosing (baseline), and on days 1, 46, 92, 106, 114 (final injections), and 2 weeks after the final injections. These tests included hemogram, serum chemistry panel, antinuclear antibodies, C3a and Bb (complement split products), activated partial thromboplas-tin time, prothrombin time, dipstick urinalysis, and a urine pregnancy test (see Supplementary Tables S1–S4 for study days and values of each test). No adverse clinical or laboratory events were noted during treatment or in the 3-month follow-up period.

Study end points for efficacy. Measures of efficacy included weekly stan-dardized digital photography, callus and nail plate length and width mea-surements during each clinic visit (carbon fiber composites digital caliper; Fisher Scientific, Pittsburgh, PA), an online, time and date stamped, sub-jective pain diary twice daily, and weekly completion of the Dermatology Life Quality Index12 (permission for use, AY Finlay). To evaluate poten-tial systemic effects, an assessment of the degree of follicular keratoses on the forearm and oral leukokeratosis was made at each clinic visit (better, worse, or the same). In an effort to minimize any inter-rater variability, clinical measurements were obtained by a single investigator (S.A.L.),

a

b

TD101-Treated (right foot)

Vehicle control (left foot)

Day 4 Day 115 Day 115

Day 4 Day 115 Day 115

Figure 3 Improvement of pachyonychia congenita symptoms follow-ing td101 administration. Callus regression is seen on the right foot at the site of injection of (a) TD101 (center arrow), but not at the site of injection of (b) vehicle on the left foot (arrows). Note that relative to the first injection, the callus on the right foot (but not on the left) developed a clearing of callus around the site of injection. The third photo in each panel is an enlargement of the site of injection from the day 115 photos. The callus on the right foot also shows some regression near the instep of the foot resulting in a shortening of the total callus length.

Molecular Therapy 5


with the exception of five measurements on days 15, 50, and 114, and two follow-up visits. The actual measure of the callus required the rater to visu-alize the point at which the callus ended and normal skin began. Because this change is gradual, the investigator had to carefully examine the skin, and then use their best judgment to determine where the callus actually began and ended.

Statistical analysis. All statistical analysis was performed using the R sta-tistical software version 2.6.0 (The R Foundation for Statistical Computing, Vienna, Austria). Scatter plots for improvement scores were augmented with smooth curves produced by the “LOESS” function in R. The differ-ence in callus length between the right and left foot was analyzed using an autoregressive model of order one, with a time-trend term. This model uses the previously occurring value as a predictor of the current value. A likeli-hood ratio test was used to determine statistical significance of the tem-poral trend during the treatment period. To plot temporal trends in callus length, we fit autoregressive models of order one to data from each foot separately. The models were piecewise linear, with a change in slope at the end of the dosing period, and were fit by maximum likelihood methods.

suPPleMentarY MaterIalTable S1. Hemogram Values.Table S2. Serum Chemistries.Table S3. Urinalysis.Table S4. Coagulation and Complement Parameters.Materials and Methods.

acKnoWledGMentsWe are indebted to the pachyonychia congenita (PC) patient that made this study possible, as well as PC Project and the membership of the International Pachyonychia Congenita Consortium for their unfail-ing enthusiasm and support. We thank Manuel Flores for assistance with preparation of figures and Kristina Heintz for her nursing support. We also acknowledge financial sponsorship of the clinical trial by PC Project and FDA (US Food and Drug Administration) OOPD (Office of Orphan Products Development) grant 1-R01-FD-003553-01 (to S.A.L.). This work was further supported by NIH (National Institutes of Health) grant 1R43ARO56559 (to R.L.K.), a fellowship grant from PC Project (to F.J.D.S.), and by grants to W.H.I.M. and F.J.D.S. from the Dystrophic Epidermolysis Bullosa Research Association, the UK Medical

Research Council (G0700314), and the British Skin Foundation. S.A.L. accepts full responsibility for the data presented in this manuscript. R.L.K., R.P.H., F.J.D.S., and W.H.I.M. have filed patents relating to short-interfering RNA therapy for PC. We thank Huntsman Cancer Institute for the use of clinical facilities for this trial. This work was completed in Salt Lake City, UT.

reFerences1. Novobrantseva, TI, Akinc, A, Borodovsky, A and de Fougerolles, A (2008). Delivering

silence: advancements in developing siRNA therapeutics. Curr Opin Drug Discov Devel 11: 217–224.

2. Nguyen, T, Menocal, EM, Harborth, J and Fruehauf, JH (2008). RNAi therapeutics: an update on delivery. Curr Opin Mol Ther 10: 158–167.

3. Whitehead, KA, Langer, R and Anderson, DG (2009). Knocking down barriers: advances in siRNA delivery. Nat Rev Drug Discov 8: 129–138.

4. Haussecker, D (2008). The business of RNAi therapeutics. Hum Gene Ther 19: 451–462.

5. Castanotto, D and Rossi, JJ (2009). The promises and pitfalls of RNA-interference-based therapeutics. Nature 457: 426–433.

6. DeVincenzo, J, Cehelsky, JE, Alvarez, R, Elbashir, S, Harborth, J, Toudjarska, I et al. (2008). Evaluation of the safety, tolerability and pharmacokinetics of ALN-RSV01, a novel RNAi antiviral therapeutic directed against respiratory syncytial virus (RSV). Antiviral Res 77: 225–231.

7. Kaspar, RL (2005). Challenges in developing therapies for rare diseases including pachyonychia congenita. J Investig Dermatol Symp Proc 10: 62–66.

8. Leachman, SA, Kaspar, RL, Fleckman, P, Florell, SR, Smith, FJ, McLean, WH et al. (2005). Clinical and pathological features of pachyonychia congenita. J Investig Dermatol Symp Proc 10: 3–17.

9. Smith, FJD, Kaspar, RL, Schwartz, ME, McLean, WHI and Leachman, SA (2006). Pachyonychia congenita. GeneReviews <www.genetests.org/profiles/pc>.

10. Cao, T, Longley, MA, Wang, XJ and Roop, DR (2001). An inducible mouse model for epidermolysis bullosa simplex: implications for gene therapy. J Cell Biol 152: 651–656.

11. Wong, P, Domergue, R and Coulombe, PA (2005). Overcoming functional redundancy to elicit pachyonychia congenita-like nail lesions in transgenic mice. Mol Cell Biol 25: 197–205.

12. Hickerson, RP, Smith, FJ, Reeves, RE, Contag, CH, Leake, D, Leachman, SA et al. (2008). Single-nucleotide-specific siRNA targeting in a dominant-negative skin model. J Invest Dermatol 128: 594–605.

13. Leachman, SA, Hickerson, RP, Hull, PR, Smith, FJ, Milstone, LM, Lane, EB et al. (2008). Therapeutic siRNAs for dominant genetic skin disorders including pachyonychia congenita. J Dermatol Sci 51: 151–157.

14. Kleinman, ME, Yamada, K, Takeda, A, Chandrasekaran, V, Nozaki, M, Baffi, JZ et al. (2008). Sequence- and target-independent angiogenesis suppression by siRNA via TLR3. Nature 452: 591–597.

15. Hickerson, RP, Vlassov, AV, Wang, Q, Leake, D, Ilves, H, Gonzalez-Gonzalez, E et al. (2008). Stability study of unmodified siRNA and relevance to clinical use. Oligonucleotides 18: 345–354.

16. Gonzalez-Gonzalez, E, Ra, H, Hickerson, RP, Wang, Q, Piyawattanametha, W, Mandella, MJ et al. (2009). siRNA silencing of keratinocyte-specific GFP expression in a transgenic mouse skin model. Gene Ther 16: 963–972.

17. Smith, FJ, Liao, H, Cassidy, AJ, Stewart, A, Hamill, KJ, Wood, P et al. (2005). The genetic basis of pachyonychia congenita. J Investig Dermatol Symp Proc 10: 21–30.

editorial

© 2011 The Society for Investigative Dermatology www.jidonline.org 995

Pachyonychia Congenita: Cast in TranslationJournal of Investigative Dermatology (2011) 131, 995. doi:10.1038/jid.2011.52

assembling a keratin network is no mean feat. The process of combining acidic and basic keratin monomers, stacking them

in an orderly fashion, and then polymerizing the bundles into rope-like intermediate filaments is an intricate operation, and one that relies on numerous cellular and subcellular processes. In many ways, the same organizational complexity is reflected in the International Consortium that over the past eight years has been assembled to decode the mysteries of the autosomal dominant keratin disorder pachyonychia congenita (PC). In this issue of JID, we present a collection of eight papers that detail the major clinical, diagnostic, mechanis-tic, and therapeutic advances that have emerged in recent years that were presented at the annual meeting of the International PC Consortium (IPCC) in May 2010.

The earliest clinical descriptions of PC appeared more than 100 years ago, and the first caus-ative mutations were reported in the mid 1990s. Subsequently, PC has been shown to involve heterozygous mutations in the KRT6A, KRT6B, KRT16, and KRT17 genes that encode keratins K6a, K6b, K16, and K17, respectively. Of course, a similar tale of careful clinical definition followed by rigorous molecular dissection has emerged for several other Mendelian skin diseases. But where the story of PC differs from that of most other gen-odermatoses is in what happened next.

Establishing the molecular basis of disease pro-vides a platform for creating in vitro and in vivo disease models, as well as translational benefits in terms of improved diagnostics and genetic coun-seling, but often pushing the translational envelope fails to overcome many of the obstacles blocking major benefits for patients, particularly toward the development of novel therapies. Thankfully for PC investigators and patients, however, substantial progress has been made, and key to this success has been the assembly of a multifunctional profes-sional cast, each with subspecialist skills sufficient to overcome therapeutic inertia or stalling.

Fundamental to the translational push has been the activity of the patient advocacy group PC Project (http://www.pachyonychia.org), which helped establish the IPCC in 2004. Working

together, the consortium subsequently assembled a network of clinicians, clinician–scientists, and scientists from a range of molecular biology, cell biology, imaging, chemistry, physics, and pharma-cological backgrounds, collectively tasked with improving understanding of the pathophysiology of PC and driving forward new therapies that can be delivered to patients.

Central to all activities, however, has been the PC patient. The IPCC has formulated a registry for patients with PC and facilitated molecular screen-ing. This has led to a significant expansion in the database of PC gene mutations, refinements in gen-otype–phenotype correlation, a new classification for PC, and a greater understanding of the impact of PC on patient quality-of-life issues, such as severity of plantar pain. But what perhaps was needed most was a clear strategy of how to develop therapies.

Modeling of PC established that mutant allele-specific silencing using RNAi approaches might be a suitable method for treating PC, and in 2010 the first human trial of siRNA for an inherited skin disease was carried out with clear clinical benefits in the treated area. Evidence was also established for some functional redundancy among certain keratins, indicating that a more generic approach in completely silencing a defective keratin was also likely to be a rational therapeutic endeavor in some other PC cases. Overhanging much of the molecular targeting, however, has been the major obstacle of effective delivery to target keratino-cytes. This is a current priority for the IPCC and a focus for its assembled crew of “delivery” experts.

As a model for how to perform translational research, the PC work has established a new paradigm for progress. Germane to all advances, however, has been the close engagement with the patient advocacy group PC Project, as well as PC patients themselves, and the multidisciplinary group of clinicians and scientists. Assembling an impressive cast of capable performers has been a considerable achievement, and now the stage is set. An expectant audience of patients and inves-tigators eagerly awaits the next act.

John A. McGrathDeputy Editor

http://www.jidonline.org

http://www.nature.com/doifinder/10.1038/jid.2011.52


The Phenotypic and Molecular Genetic Featuresof Pachyonychia CongenitaW.H. Irwin McLean1, C. David Hansen2, Mark J. Eliason2 and Frances J.D. Smith1

Pachyonychia congenita (PC) is an autosomal domi-nant genodermatosis caused by heterozygousmutations in any one of the genes encoding thedifferentiation-specific keratins K6a, K6b, K16, or K17.The main clinical features of the condition includepainful and highly debilitating plantar keratoderma,hypertrophic nail dystrophy, oral leukokeratosis, and avariety of epidermal cysts. Although the conditionhas previously been subdivided into PC-1 and PC-2subtypes, the phenotypic characterization of 1,000mutation-verified PC patients enrolled in the Interna-tional PC Research Registry, coordinated by thepatient advocacy group PC Project, shows that thereis considerable overlap between these subtypes.Thus, a new genotypic nomenclature is proposed, inwhich PC-6a represents a patient carrying a mutationin the K6a gene, etc. Although a rare disorder, PCrepresents a good model for therapy development,and international efforts are ongoing to develop anddeliver siRNA, gene, correction, small molecule, andother strategies to treat this painful, disablingskin condition. The special relationship between PCProject and the PC research community has greatlyaccelerated the development pathway from geneidentification to clinical trials in only a few years andrepresents a paradigm of hope for other orphandiseases.

Journal of Investigative Dermatology advance online publication, 24 March2011; doi:10.1038/jid.2011.59

INTRODUCTIONPachyonychia congenita (PC) is an uncommon autosomaldominant disorder of keratinization caused by mutations inany one of a number of keratin genes that are expressedin differentiated epithelial tissues. The condition was firstdescribed in the early twentieth century (Jadassohn and

Lewandowski, 1906; Jackson and Lawler, 1951) but it wasnot until the early 1990s, with the emergence of moleculargenetics technology, that the causative gene in a largeScottish PC family was mapped to one of the keratin geneclusters (Munro et al., 1994). Shortly thereafter, the causativemutations were identified in several PC patients in the KRT6A,KRT6B, KRT16, and KRT17 genes, encoding the keratinproteins K6a, K6b, K16, and K17, respectively (Bowdenet al., 1995; McLean et al., 1995; Smith et al., 1998).

Keratins are the intermediate filament proteins specificallyexpressed by epithelial cells, in which they form a densecytoplasmic network (Irvine and McLean, 1999; Omary et al.,2004). The primary function of the keratin cytoskeleton is toimpart mechanical strength and resilience to epithelial cellsand tissues. Disruption of this cytoskeletal system due to agenetic mutation in a keratin gene leads to extreme fragility ofthe epithelial cells and tissues in which the mutated keratin isexpressed. Similar to several other keratin disorders, thevast majority of causative mutations in the PC-related keratinsare heterozygous missense mutations or small insertion/deletion mutations that disrupt cytoskeletal function viadominant-negative interference and lead to epithelial cellfragility (McLean et al., 2005). In PC, this is manifest ascytolysis and hyperkeratosis in the subset of differentiatedepithelial tissues in which K6a, K6b, K16, and K17 arepredominantly expressed (Lane, 1993), specifically thepalmoplantar epidermis, nail bed, mucosae, and the pilose-baceous unit. Thus, the cardinal phenotypic featuresof PC are palmoplantar (predominantly plantar) keratoderma;hypertrophic nail dystrophy; oral leukokeratosis; and avariety of cysts arising from hyperkeratosis of pilosebaceousapparatus (Figure 1).

A MOLECULAR CLASSIFICATION FOR PC SUBTYPESIn 2003, a patient advocacy group—Pachyonychia CongenitaProject—was established to support those affected by PCand to both encourage and fund research into a cure for thecondition (www.pachyonychia.org). To achieve this goal,the International PC Consortium (IPCC) was founded in early2004. This is a group of clinicians and scientists activelyresearching the causes of PC and importantly, the developmentof new treatments for PC. The IPCC has met annually since2004 and its membership is listed at www.pachyonychia.org.

An important part of the ongoing PC research program isthe International PC Research Registry (IPCRR), in whichdetailed phenotypic data are collected from patients andlinked to genetic data. At the time of writing, close to 1000PC patients have been identified by the PC Project. This has

& 2011 The Society for Investigative Dermatology www.jidonline.org 1

REVIEW

Received 26 August 2010; revised 2 February 2011; accepted 11 February2011

1Division of Molecular Medicine, University of Dundee, Dundee, UK and2Department of Dermatology, University of Utah, Salt Lake City, Utah, USA

Correspondence: W.H. Irwin McLean, Division of Molecular Medicine,Medical Sciences Institute, University of Dundee, Dundee DD1 5EH, UK.E-mail: [email protected]

Abbreviations: IPCC, International Pachyonychia Congenita Consortium;IPCRR, International Pachyonychia Congenita Research Registry; K, keratinprotein; KRT, keratin gene; PC, pachyonychia congenita

http://dx.doi.org/10.1038/jid.2011.59

www.pachyonychia.org




led to the largest collection of linked clinical and geneticinformation yet assembled for a rare keratin disorder.Historically, PC has been split into two subtypes (PC-1, orJadassohn–Lewandowski subtype; and PC-2, or the Jackson–-Lawler subtype) on the basis of subtle differences inphenotype, primarily the presence or absence of pilosebac-eous cysts (Jadassohn and Lewandowski, 1906; Jacksonand Lawler, 1951). At present, with analysis of hundreds ofpatients in the IPCRR, limitations in the older classification,which was based on only a handful of non-genotyped cases,have become clear. In particular, many PC patients,regardless of genotype, have some form of epidermal cysts(see Wilson et al., 2011). Therefore, on the basis of the morecomprehensive IPCRR data, a more rational and usefulclassification based on the mutated gene was proposed atthe 2010 IPCC Symposium and has been adopted throughoutthe research papers in this issue of the JID. The newclassification is PC-6a, PC-6b, PC-16, and PC-17, for a patientwith a mutation in the gene encoding K6a and others proteins(the complete data set underlying this new nomenclaturewill be published elsewhere; Eliason et al., unpublished data).In cases in whom PC is suspected but no mutation has beenfound (or not looked for), the term PC-U (for unknown) willbe used.

The predominant symptom in PC is plantar pain

Although hypertrophic nail dystrophy is the phenotypicfeature that gave rise to the name of the condition, the most

problematic symptom reported by PC patients is focal plantarkeratoderma that is associated with severe pain. The plantarpain in PC is often highly debilitating and has considerablenegative effect on quality of life. The reason for the pain is notfully understood but is thought to be related to blisterformation deep underneath the thick callus that developsover the pressure points of the plantar surface (see Figure 1a).Plantar blistering, together with accompanying pain, is acommon feature of PC that is under-reported in the literature(Eliason et al., unpublished data).

Nail dystrophy (Figure 1b), which can occur from a veryearly age, is variable in severity and in many cases not all 20nails are affected. Toenails are more commonly affected thanfingernails, which could be because of greater trauma exertedfrom shoes. Another feature of PC is oral leukokeratosis(Figure 1c). This is often one of the first signs of PC in babiesand may lead to difficulty in feeding and is often mistaken forcandidiasis in infants. Follicular keratoses are present inmany cases of PC. Some individuals also develop cysts in theform of steatocysts (steatocystomas) and/or pilosebaceouscysts (Figure 1d). This feature is particularly associated withpatients with a K17 mutation (see Wilson et al., this issue), inwhom sometimes it is necessary to remove cysts surgically.The severity of the clinical features of PC can vary quitewidely both among and within families. This may partly bebecause of individual lifestyle and care of PC and could alsobe because of the specific type of mutation, as well as othergenetic and/or environmental factors.

a b

d

c

Figure 1. The cardinal clinical characteristics of PC. (a) Focal plantar keratoderma, with recurrent blistering underneath the callus, is the main source of

pain and disability in PC. This individual is a heterozygous carrier of the K16 mutation L132P (p.Leu132Pro). (b) Typical hypertrophic nail dystrophy that

gives the condition its name. The nail changes are quite variable in PC families, even among people with the same mutation. In some cases, the fingernails

are spared. This patient carries the K17 mutation L95Q (p.Leu95Gln). (c) Oral leukokeratosis is a common feature of PC, readily seen here as lingual

leukokeratosis in a patient carrying the most common PC mutation, N172del (p.Asn172del) in K6a. (d) PC patients suffer from a variety of epidermal cysts,

including follicular keratoses and pilosebaceous cysts that can resemble steatocysts or epidermoid cysts. The latter are more abundant in patients with

K17 mutations, as shown here in a patient carrying the K17 mutation N92D (p.Asn92Asp). PC, pachyonychia congenita.

2 Journal of Investigative Dermatology

W.H. Irwin McLean et al.Clinical and Genetic Features of PC

Rapid therapy development in PCAlthough it is a rare condition, PC is at the forefront ofgenetic therapy development in the dermatology field.In particular, the dominant-negative genetic mechanism inPC contributes to therapeutic strategies based on RNAinterference (RNAi), especially in the form of short interferingRNA (siRNA). It has been demonstrated that mutant keratinalleles differing from wild type by a single-nucleotide pointmutation can be potently and specifically silencedby carefully designed siRNA (Hickerson et al., 2008). Thismutation-specific siRNA therapy approach has been pro-gressed into the recently reported small-scale human clinicaltrial, in which efficacy was demonstrated (Leachman et al.,2010). This was the first time that siRNA had been used totreat a human skin disorder. The keratins involved in PC alsoshow considerable functional redundancy, in particular whenK6 is involved. Humans have three copies of a nearlyidentical KRT6 gene, encoding the K6a, K6b, and K6cproteins. Mouse knockout experiments strongly suggest thatloss of one of these keratins may be tolerated (Wong et al.,2000; Wojcik et al., 2001) and therefore an alternativetherapeutic approach would be to completely silence thedefective keratin, regardless of mutation. To this end, highlypotent gene-specific siRNA has been developed for PC (Smithet al., 2008). The major technical hurdle yet to overcome inboth these therapeutic approaches is the development of asafe, effective, and patient-friendly method for routinedelivery of siRNA into the epidermis. This is currently amajor goal of the IPCC research groups, in addition todevelopment of alternative therapies that include genecorrection methodology, small molecule therapy, and otherstrategies (Kaspar et al., this issue).

CONCLUSIONOver the past 7 years, the PC research field represents a greatexample of how a small group of highly motivated patients andtheir families, together with a group of interested clinicians andscientists, can rapidly progress research from knowing only theidentity of a gene defect to having new therapies that showefficacy in cells, in animal models, and in patients. Hopefully,this sustained, highly focused effort will shortly lead to asuccessful and widely applicable treatment for PC and thelessons learned along the way can be translated to other geneticskin disorders.

CONFLICT OF INTERESTDr McLean and Dr Smith filed a patent on therapeutic siRNA for PC. Theother authors state no conflict of interest.

ACKNOWLEDGMENTSWe thank Pachyonychia Congenita Project for their continued enthusiasm,constant encouragement, and financial support of their research.

REFERENCES

Bowden PE, Haley JL, Kansky A et al. (1995) Mutation of a type II keratin gene(K6a) in pachyonychia congenita. Nat Genet 10:363–5

Hickerson RP, Smith FJD, Reeves RE et al. (2008) Single-nucleotide-specificsiRNA targeting in a dominant-negative skin model. J Invest Dermatol128:594–605

Irvine AD, McLean WHI (1999) Human keratin diseases: the increasingspectrum of disease and subtlety of the phenotype-genotype correlation.Br J Dermatol 140:815–28

Jackson ADM, Lawler SD (1951) Pachyonychia congenita: a reportof six cases in one family with a note on linkage data. Ann Eugen16:142–6

Jadassohn J, Lewandowski F (1906) Pachyonychia congenita: keratosisdisseminata circumscripta (follicularis). Tylomata. Leukokeratosis lin-guae. vol. 1. Berlin: Urban and Schwarzenberg, 29

Kaspar RL, Leachman SA, McLean WHI, Schwartz ME (2011) Toward aTreatment for Pachyonychia Congenita: Report on the 7th AnnualInternational Pachyonychia Congenita Consortium Meeting. J InvestigDermatol 131:1011–4

Lane EB (1993) Keratins. In Connective Tissue and its Heritable Disorders.Molecular, Genetic and Medical Aspects. Royce PM, Steinmann B (eds).New York: Wiley-Liss Inc, 237–47

Leachman SA, Hickerson RP, Schwartz ME et al. (2010) First-in-humanmutation-targeted siRNA phase Ib trial of an inherited skin disorder.Mol Ther 18:442–6

McLean WHI, Rugg EL, Lunny DP et al. (1995) Keratin 16 and keratin17 mutations cause pachyonychia congenita. Nat Genet 9:273–8

McLean WHI, Smith FJD, Cassidy AJ (2005) Insights into genotype-phenotype correlation in pachyonychia congenita from the humanintermediate filament mutation database. J Investig Dermatol Symp Proc10:31–6

Munro CS, Carter S, Bryce S et al. (1994) A gene for pachyonychia congenitais closely linked to the keratin gene cluster on 17q12-q21. J Med Genet31:675–8

Omary MB, Coulombe PA, McLean WHI (2004) Intermediatefilament proteins and their associated diseases. N Engl J Med 351:2087–100

Smith FJD, Hickerson RP, Sayers JM et al. (2008) Development oftherapeutic siRNAs for pachyonychia congenita. J Invest Dermatol 128:50–8

Smith FJD, Jonkman MF, van Goor H et al. (1998) A mutation in humankeratin K6b produces a phenocopy of the K17 disorder pachyonychiacongenita type 2. Hum Molec Genet 7:1143–8

Wilson NJ, Leachman SA, Hansen CD et al. J Invest Dermatol; e-pub ahead ofprint 17 February 2011

Wojcik SM, Longley MA, Roop DR (2001) Discovery of a novel murinekeratin 6 (K6) isoform explains the absence of hair and nail defects inmice deficient for K6a and K6b. J Cell Biol 154:619–30

Wong P, Colucci-Guyon E, Takahashi K et al. (2000) Introducing a nullmutation in the mouse K6alpha and K6beta genes reveals their essentialstructural role in the oral mucosa. J Cell Biol 150:921–8

www.jidonline.org 3

W.H. Irwin McLean et al.Clinical and Genetic Features of PC


FEATURE ARTICLE

Pachyonychia Congenita ProjectA Partnership of Patient and Medical Professional

Mary E. Schwartz, Gail M. Zimmerman, Frances Smith, Eli Sprecher

ABSTRACT: A rare disease like pachyonychia congenita(PC) poses barriers to the patient, medical professional,and scientist. The patient has challenges connecting toinformation, the medical professional has challengesconnecting to patient experience, and the scientist haschallenges connecting to a sufficient number of pa-tients to do meaningful research. Recent collaborationbetween these groups has transformed our under-standing of PC and its symptoms and method of diag-nosis. PC Project is at the center of this collaborationand is providing new insights for the dermatologist anddermatology nurse, enabling better diagnosis of PCand counseling of a PC patient. The PC patient, medi-cal professional, and scientist have an internationaladvocate in PC Project, a patient-led, nonprofit projectcommitted to connecting all these communities to thetools they need to improve the lives of those living with PC.Key words: Blisters, Cysts, Keratoderma, Nail dystrophy,Pachyonychia, Partnership

‘‘I was one proud mama! I watched myson hand PC brochures out to people (atour PC Awareness Day Event). When theyasked questions, he answered them. If mygrandmother was still alive she would be so

proud to know how far we’ve come. No longerare we sitting on fingers at the dinner table,hiding our PC as she didIinstead we aresharing with anyone information about PC,proud that we have an organization thatstands by us. And, most importantly, we arenot alone with PC. It may be rareIbut wehave met friends with it thanks to last year’sPC Patient Support Meeting. We are notalone!’’ (Jessica, pachyonychia congenita[PC] patient).

These words of joy reflect the power that cancome from shared experienceVknowing youare part of a larger community. This joy ofknowing can be especially empowering whenliving with a rare disease like PC.

PC is an ultra-rare skin disorder that affects 2,000Y10,000people worldwide. The rarity of PC means that a personwith PC usually never meets anyone else with PC otherthan affected family members. It means that researchersare challenged to find a sufficient number of PC patientsto do meaningful research. It means that medical pro-fessionals do not have easy access to broad patient expe-rience onwhich to base diagnosis or to learn if a treatmentreally works.

In 2004, PC Project [a patient-led 50l(c)(3) charity basedin Salt Lake City, Utah] set out to eliminate these barriersof isolation by creating an international collaborative net-work of patients, medical professionals, and scientists tobe a catalyst to find effective treatments for the disease.Using high-technology tools, including custom softwarefor the PC registry and database, an interactive Web site(www.pachyonychia.org), Webinars, and Web meetings(as well as E-mail, conference calls, and VoIP services orSkype), PC Project has connected researchers interestedin keratin disorders, multidisciplinary specialists, and der-matologists to conduct basic and clinical research. Thisgroup of specialists is known as the International PCConsortium (IPCC). PC Project has also identified andrecruited patient volunteers to provide personal historiesand has in turn provided physician consultations and

42 Journal of the Dermatology Nurses’ Association

Mary E. Schwartz, AA, Pachyonychia Congenita Project, SaltLake City, Utah.Gail M. Zimmerman, BA, Pachyonychia Congenita Project, SaltLake City, Utah.Frances Smith, PhD, Division of Molecular Medicine, Universityof Dundee, Dundee, United Kingdom.Eli Sprecher, MD, PhD, Department of Dermatology, Tel AvivSourasky Medical Center, Tel Aviv, Israel, and Sackler Faculty ofMedicine, Tel Aviv University, Ramat Aviv, Israel.

Conflicts of interest and sources of funding: There are no conflictsof interest. PC Project is a 501(c)(3) U.S. public charity. Fundingsources are from donations as well as grants from the NationalInstitutes of Health.

Correspondence concerning this article should be addressed toMary E. Schwartz, AA, Pachyonychia Congenita Project, 2386 E.Heritage Way, Suite B, Salt Lake City, UT 84109.E-mail: [email protected]

DOI: 10.1097/JDN.0b013e31827d9ed5

Copyright © 2013 Dermatology Nurses' Association. Unauthorized reproduction of this article is prohibited.


genetic testing for these patients through the InternationalPC Research Registry (IPCRR). PC Project continues toseek dermatologists and dermatology nurses to be part-ners in this international community.

Through this collaborative effort, researchers have madeseveral discoveries that have transformed the understandingof PC and treatment for PC. These new insights have sig-nificance for the dermatologist and dermatology nurse indiagnosing and counseling a PC patient.

PC: WHAT WE HAVE LEARNEDThe disease is characterized by accumulation of keratinin the skin and nails, which manifests as calluses, thick-ened nails, and cysts (see Figures 1Y3). Under the callusesare extremely painful blisters on the soles and sometimeson the palms. Pain is one of the most consistent features ofPC and a key in differential diagnosis (Eliason, Leahman,Feng, Schwartz, & Hansen, 2012). PC is caused by a sin-gle mutation in one of at least five keratin genes, KRT6A,KRT6B, KRT6C, KRT16, or KRT17 (Akasaka et al.,2011; Wilson et al., 2010, 2011). As PC is an autosomal-dominant disorder, there is a 50% chance of passing onthe mutation with each conception. However, more than45% of PC cases appear spontaneously where there is nofamily history of the disease.

The condition was first described in the early 20th cen-tury (Jadassohn & Lewandowski, 1906) as ‘‘pachyo-nychia,’’ which means ‘‘thickened nails.’’ However, PC

refers to a spectrum of symptoms, which is determined byboth the location and the nature of the causative mutationas well as by yet unknown additional genetic and envi-ronmental factors (which explain the fact that individualscarrying the very same mutation can display divergent clin-ical features). From detailed questionnaires gathered fromnearly 500 patients participating in the IPCRR, those withgenetically confirmed PC are consistently found to have atriad of features including nail dystrophy, palmar/plantarkeratoderma (e.g., thickening of the skin), and pain.

PC shares symptoms with a number of disorders likeepidermolysis bullosa simplex and some connexin disor-ders (e.g., Clouston syndrome). In PC, the unrelentingpain from blisters under the thick calluses on the soles ofthe feet is the principal life-altering feature for most withthis disease. The callus usually begins when the child withPC first begins towalk, and the pain is usually constant byage of 10 years. It requires regular trimming of the callusand activity planning to limit time on one’s feet. Manymust use canes, crutches, or wheelchairs or must crawl ontheir knees to manage the pain. In some forms of PC, theprevalent cysts are the most painful feature.

Documenting the variability of the symptoms acrossmutations and genes has led to a new classification systemof PC to help clinicians improve their diagnostic and prog-nostic accuracy and improve therapeutic development.Rather than refer to PC-l and PC-2, which inaccuratelygroups PC patients, the new nomenclature, a diagnosis of

FIGURE 1. Focal plantar keratoderma, with painful blistering underneath the callus, is the main source of pain anddisability in PC. Palmar keratoderma may also be found in patients with PC. Abbreviation: PC = pachyonychiacongenita.

VOLUME 5 | NUMBER 1 | JANUARY/FEBRUARY 2013 43


PC-K6a, PC-K6b, PC-K6c, PC-K16, and PC-K17, corre-sponds to mutations in the KRT6A, KRT6B, KRT6C,KRT16, and KRT17 genes, respectively, and PC-U indi-cates thosewith an unconfirmed geneticmutation (McLean,Hansen, Eliason, & Smith, 2011).

THE ROLE OF THE DERMATOLOGY NURSEAlthough there is no effective treatment for PC at thistime, the dermatology nurse can be a very helpful partnerto the PC patient by helping with diagnosis, care tech-niques, and provision of accurate information. Those withPC may require medical assistance when they experiencean infection of the nails or cysts. A good relationship witha dermatology nurse can be extremely beneficial to pa-tients with PC.

Also, the dermatology nurse can effectively assist thepatient in participating in the IPCRR. Through the IPCRR,the patient can obtain genetic testing to determine whetherthe patient has a mutation in one of the genes associatedwith PC. Details regarding the gene and the specific mu-tation are providedwith the test results, and genetic counsel-ing is available. If the patient is found not to have PC,genetic testing is conducted for a number of other similarconditions with the overall goal to assist the patient andmedical providers with a definitive answer regarding thecondition. All PC Project services are provided at no costto the patient and referring specialist.

The IPCC experts welcome the opportunity to supportthe nurse and/or doctor in diagnosis, treatment options,and care. The dermatologist or dermatology nurse may

contact us directly or refer the patient to PC Project. Indi-vidual consultations for patients, physicians, and derma-tology nurses treating PC patients may be scheduled withphysicians serving on the PC Project Medical and Scien-tific Advisory Board.

Once the diagnosis of PC is confirmed, the PC patient’sde-identified data will be made available to researchersaround the world (while preserving patient privacy andanonymity), and the patient will be eligible to participatein future studies and clinical trials.

DiagnosisIt is not uncommon for a person to reach his or her 40s or50s before getting a correct diagnosis. Data from patientsparticipating in the IPCRR have now revealed that plantarpain is a key diagnostic clue. In a recent study of 254 PCpatients, plantar pain was reported by 225 of 254 (89%)surveyed patients. Only three patients older than 10 yearsold did not report plantar pain. The researchers concludedthat plantar pain is the most important feature of PC af-fecting quality of life. The pain is related to the underlyingblisters, and the thickness or extent of the visible callusmay not reflect the degree of pain a patient experiences(Eliason et al., 2012).

Main Features of PCBecause of the IPCRR, the clinician who only rarely en-counters these disorders now has better guidance and amore robust framework tomake a clinical diagnosis (Irvine,2012, p. 1758).

FIGURE 2. Nail changes in PC are quite varied across PC patients even among family members or those with the samemutations. Abbreviation: PC = pachyonychia congenita.

FIGURE 3. PC patients experience a variety of epidermal cysts. Those with PC-K17 have the greatest abundance ofsteatocystomas. Abbreviation: PC = pachyonychia congenita.



� Nail dystrophy (or thickening) often does not affectall 10 fingernails or all 10 toenails.

� Only toenails may be affected with fingernails re-maining normal.

� Calluses on the soles of feet have underlying hiddenblisters and are usually extremely painful with plantarpain being the number one concern for PC patients.

� Cysts are the second most common cause of pain inPC, and pain may also be from infected nails or fol-licular hyperkeratosis.

� Both steatocystoma and pilosebaceous cysts are foundin nearly all types of PC, although those with PC-K17have a greater number of steatocystomas.

� Nail infections may be initiated by nail trauma or ex-cessive trimming.

Other Features of PC

� Follicular hyperkeratosis (most prominent in chil-dren and young teens)

� Oral leukokeratosis (often misdiagnosed as thrush orleukoplakia)

� Prenatal or natal teeth (usually PC-K17)� Acute pain related to ‘‘first bite syndrome’’ (often mis-diagnosed as ‘‘ear’’ pain)

� Laryngeal problems: thickening or nodules on thevocal chords causing hoarseness or, sometimes, dif-ficulty in breathing (Treatment of the larynxmay causeincreased overgrowth but may sometimes be neces-sary to avoid obstruction.)

The rarity of the disease and its overlapping symptomswith other skin disorders make diagnosis a challenge.Commonly, people with PC may be misdiagnosed withonychomyciosis or fungal infection of the nails or withother causes for palmar/plantar keratoderma. At the sametime, people with only thickened or dystrophic nails maybe told that they have PC. Furthermore, previously mis-attributed features such as deafness, mental retardation,diabetes, bony abnormalities, early menarche, corneal le-sions, and cataracts can be safely excluded from the canonof PC manifestations (Irvine, 2012, p. 1758).

Genetic testing can confirm the clinical diagnosis of PCand is the only way to verify that the patient’s condition isin fact PC and not a related disorder.

TreatmentReview of the experience of PC patients in the IPCRR hasshown that, although traditional therapeutics such asurea, salicylic acid, or oral retinoids may soften or reducecalluses, most patients abandon those therapies for lack ofsufficient benefit (Eliason et al., 2012). When oral reti-noids were recently assessed, findings show that, for mostpatients, there was no benefit and, instead, increased painor the adverse side effects outweighed the benefits (Gruberet al., 2011). Because we cannot predict which patients

may benefit from oral retinoids, an empirical trial withvariable dosing is being evaluated as well as a topical ret-inoid application for PC.

Patients typically manage their own symptoms throughcareful mechanical trimming of the calluses to ensure a‘‘not too thick and not too thin’’ result. Aggressive debride-ment may increase pain. Frequent filing and trimming ofthe nails is also necessary. Patients who experience PCwithnumerous cysts find that these must be drained or the cystsmay need to be surgically removed because of pain orinfection.

The results of a formal survey of patient experience withtreatment and self-care will also be published soon. Thesurvey collected detailed responses on treatment and careused by PC patients for specific conditions including ker-atoderma; cysts; follicular hyperkeratosis; and fingernails,toenails, and nail infections. The results will be publishedshortly and will provide a good reference for both thedermatologist and dermatology nurse.

Patients may need one or more medical services on aregular basis including quick access to prescriptions forantibiotics when infections arise, removal of cysts, painmedication, or other care related to the varied symptomsof PC. The dermatology nurse/dermatologist may need tohelp the PC patient find treatment for one ormore of theseissues.

PC PROJECT: A RESOURCE FOR THE PC PATIENTAND MEDICAL PROFESSIONALMajor benefits for PC patients and medical professionalsare available through the PC Project, the IPCRR, andIPCC members. Participation in the IPCRR provides ac-cess to clinical trials, information on care techniques, publi-cations from dermatology journals, annual patient supportmeetings, andWebinars. Through the IPCC, medical pro-fessionals have a team of support and information for theirpatients’ care.

Through the Web site (www.pachyonychia.org), boththe patient and medical professional can stay informedabout opportunities to participate in educational meet-ings, Webinars, and clinical trials. The Web site featuresthe latest research news, extensive images, a complete bib-liography of scientific articles, patient education brochures,a quarterly scientific newsletter, and a monthly news briefas well as an annual report. PC Project also maintains aFacebook page through which PC patients in the IPCRRcan connect with each other.

Patient success with various care techniques does vary.To help PC patients find what may work for them, PCProject has catalogued patient reports into a PCWiki sec-tion available on theWeb site. Techniques used to managethe symptoms of PC are shown on a ‘‘Caring For PC’’DVD, which is available upon request. The DVD and allprinted materials are provided at no charge to patients andmedical professionals.




The annual PC Patient Support Meeting (in Europe orthe United States) is an especially important way a PC pa-tient can meet, connect, and share with others who havePC. To help every PC patient who wants to attend, PCProject offers scholarships to patients in the IPCRR toattend the meeting.

To learn directly from physician experts about PC, in-terested dermatology nurses can sign up for one of thequarterly educational Webinar sessions sponsored by PCProject. There are also educational brochures specificallyfor medical professionals. In addition, for patients in theIPCRR, medical experts are available to provide counsel-ing with a physician or nurse to individual patients.

We recognize that most medical professionals will rarelysee a PC patient, so PC Project has set up a resource forthose medical professionals wanting to confirm diagnosisor get the latest advice on management of the disease orclinical trials that may be ongoing.

WORKING TO CHANGE THE FUTURE: MAINTAININGRESEARCH MOMENTUMPC Project is collaborating on a number of research strat-egies to develop an effective PC treatment. One of theseresearch strategies is gene silencing. By inactivating themutant keratin gene, researchers hope to eliminate PCsymptoms. PC Project, through its biotech partner Trans-Derm, has completed a Phase 1b, FDA-approved clinicaltrial of a gene silencing strategy using siRNA therapy(Leachman et al., 2010). A second clinical trial of an im-proved siRNA developed by TransDerm will begin in2013 (Hickerson et al., 2011). This second trial will in-volve use of dissolvable microneedles developed to de-liver drugs in a more patient-friendly manner (Gonzalezet al., 2010). Two additional clinical studies (oral statinsand topical rapamycin) will also enroll patients in 2013.

PC Project provides fellowship and grant funding to avariety of universities for the support of PC research. Since2004, when the IPCC was formed with 23 physicians andresearchers, PC Project has recruited 150 members of theconsortium, each with a pledge to collaborate to improvetreatment for PC. A number of ground-breaking basic andclinical research reports have been published in the lastcouple of years by members of the IPCC in leading der-matology journals. These reports are accessible to every-one through a searchable bibliography on the PC Project’sWeb site or can be requested on a CD or in booklet format.

Topics of articles, which will be published shortly basedon the results of current studies, include PC best practices,life history of PC, pathology of PC nails, pathology of PCcysts, and over 50 additional case studies including novelmutations as well as a revised PC summary article. TheNational Institutes of Health Office of Rare Disease Re-search and National Institutes of Health/National Instituteof Arthritis and Musculoskeletal and Skin have been veryhelpful to PC Project in our research and outreach efforts.

RAISING RARE DISEASE AWARENESSAs PC is ultra-rare, the public and medical community aregenerally not aware of PC or the challenges it can present.This lack of awareness contributes to the isolation of manyPC patients. The empathy and understanding of the generalpublic will create a more supportive environment for thoseexperiencing rare diseases like PC and generatemore publicsupport of rare disease research.

Raising funds for rare disease research and patient sup-port has been challenging in terms of recruiting volunteersand supporters. However, because of the profound impactthis disease can have on the life of both children and adults,parents, spouses, and family members are highly moti-vated to help improve their future. PC Project launched itsfirst annual PC Awareness Day in 2012 to begin connect-ing and empowering the PC patient community in itssupport of public awareness. This first international effortresulted in dozens of local events in 10 countries andreached thousands around the world through print, TV,and radio media. PC Project just completed a 5- to 6-minute public awareness video on PC that can be foundonYouTube. PCAwareness Day provided a new source offunds as well as an opportunity to increase awareness ofPC. All 2012Y2013 donations are matched $2-for-$1 byan anonymous individual sponsor, which triples each dollarreceived.

PC Project participates with other nonprofit groups,which specialize in areas important to PC research andpatient support. These include Genetic Alliance (focuseson genetic disorders), National Organization for RareDisorders (focuses on rare disorders), and the Coalitionof Skin Diseases (focuses on skin disease research andpatient advocacy). The American Academy of Dermatol-ogy and the Society of Investigative Dermatology areimportant partners in the effort to raise awareness andprovide support for skin disease research. The best partof PC Project is the partnershipsVhelping people con-nect with each other and to connect the patients andscientists. PC Project was started to help one person, butnow, it serves and unites more than 1,000 people with PCin over 50 countries. People with PC need to know that,by sharing information andworking with others in the PCcommunity, they can advance research and change thefuture. The growing number of patients, physicians, andscientists in our network of collaborators will move usmore rapidly to an effective, patient-friendly treatment. h

REFERENCES

Akasaka, E., Nakano, H., Nakano, A., Toyomaki, Y., Takiyoshi, N.,Rokunohe, D., & Sawamura, D. (2011). Diffuse and focal palmo-plantar keratoderma can be caused by a keratin 6c mutation. BritishJournal of Dermatology, 165(6), 1290Y1292. doi: 10.1111/j.1365-2133.2011.10552.x.

Eliason, M. J., Leachman, S. A., Feng, B. J., Schwartz, M. E., & Hansen,C. D. (2012). A review of the clinical phenotype of 254 patients withgenetically confirmed pachyonychia congenita. Journal of the AmericanAcademy of Dermatology, 67, 680Y686. doi: 10.1016/j.jaad.2011.12.009.



Gonzalez-Gonzalez, E., Speaker, T. J., Hickerson, R. P., Spitler, R., Flores,M. A., Leake, D., & Kaspar, R. L. (2010). Silencing of reporter geneexpression in skin using siRNAs and expression of plasmid DNA de-livered by a soluble protrusion array device (PAD). Molecular Therapy,18(9), 1667Y1674. doi: 10.1038/mt.2010.126.

Gruber, R., Edlinger, M., Kaspar, R. L., Hansen, C. D., Leachman, S.,Milstone, L. M., & Schmuth, M. (2011). An appraisal of oral retinoidsin the treatment of pachyonychia congenita. Journal of the AmericanAcademyofDermatology, 66, e193Y199. doi: 10.1016/j.jaad.2011.02.003.

Hickerson, R. P., Flores, M. A., Leake, D., Lara, M. F., Contag, C. H.,Leachman, S. A., & Kaspar, R. L. (2011). Use of self-delivery siRNAsto inhibit gene expression in an organotypic pachyonychia congenitamodel. Journal of Investigative Dermatology, 131(5), 1037Y1044. doi:10.1038/jid.2010.426.

Irvine, A. D. (2012). Double trouble: Homozygous dominant mutationsand hair loss in pachyonychia congenita. Journal of Investigative Der-matology, 132(7), 1757Y1759. doi: 10.1038/jid.2012.121.

Jadassohn, J. L. F. (1906). Pachyonychia congenita: Keratosis disseminata

circumscripta (follicularis). In Tylomata. Lukokeratosis linguage (Vol. 1,p. 29). Berlin, Germany: Urban and Schwarzenberg.

Leachman, S. A., Hickerson, R. P., Schwartz, M. E., Bullough, E. E.,Hutcherson, S. L., Boucher, K. M., & Kaspar, R. L. (2010). First-in-human mutation-targeted siRNA phase 1b trial of an inherited skin dis-order. Molecular Therapy, 18(2), 442Y446. doi: 10.1038/mt.2009.273.

McLean, W. H., Hansen, C. D., Eliason, M. J., & Smith, F. J. (2011). Thephenotypic and molecular genetic features of pachyonychia congenita.Journal of Investigative Dermatology, 131(5), 1015Y1017. doi: 10.1038/jid.2011.59.

Wilson, N. J., Leachman, S. A., Hansen, C. D., McMullan, A. C.,Milstone, L. M., Schwartz, M. E., & Smith, F. J. (2011). A large mu-tational study in pachyonychia congenita. Journal of InvestigativeDermatology, 131(5), 1018Y1024. doi: 10.1038/jid.2011.20.

Wilson, N. J., Messenger, A. G., Leachman, S. A., O’Toole, E. A., Lane, E.B., McLean, W. H., & Smith, F. J. (2010). Keratin K6c mutations causefocal palmoplantar keratoderma. Journal of Investigative Dermatology,130(2), 425Y429. doi: 10.1038/jid.2009.215.



Pachyonych Congenita Overview

• la

The inherited nail dystrophy is a~sociated with painful plantar keratoderma.

MARY E. SCHWARTZ, LLD, C DAVID HANSEN, MD, AMY S. PALLER, MD, FRANCESJ D. SMITH, PHD, AND ELI SPRECHER, MD, PHD

36 April 20 14 I THE DERMATOLOGIIT" I www.the-dermotologist.com

Pachyonychia congenita (PC) is a . rare skin disorder caused by muta

tions affectmg a group of keratins found in specific regions of the epidermis. Although originally classified as a nail dystrophy, its major impact on adu lt patients is from painful plantar keratoderma. Other manifestations also commonly occur. This article reviews the clinical presentation, genetic diagnosis, pathogenesis and current and future treatment options for Pc.

CLINICAL PRESENTATION Data ga thered by the International

PC Research R egistry (IPCRR) on n1.ore than 600 individuals with genetically confirmed PC show that PC always includes at least lather feature along with nail dystrophy. I

The most debilitating condition for those with PC is exquisitely painful plantar keratoderma. In some cases, this is the predominant clinical presentation ' with little or no nail dystrophy.2.3 Other COlTIJnon manifestations of PC are extensive cysts including steatocysts, leukokeratosis, follicular hyperkeratosis and palmar keratoderma (Figures 1-7) .1 However, only thickened nails may be evident in neonates and infants with PC4 Natal teeth may also be present at birth, predominantly in one PC subtype.

Leukokeratosis is another finding for PC infants and is often misdiagnosed and treated as thrush. Although florid leukokeratosis has often been incriminated as the cause of difficulty in feeding during il"lfancy, especially with laryngeal involvement, an alternative underlying cause is a painful "first bite syndrome" experienced by some PC children. This is being assessed in a series of unpublished cases in the IPCRR. In each of these patients, a change to soft rupples with large holes inU11.ediately resolved the feeding problem.

Blisters or callus on the feet usually begin when a child with PC fIrSt begins to walk and the age of onset of plantar keratoderma is a fimction of the extent of weight on the feet. The pain is usually constant by age 10.4 Many adults with PC rely on canes, crutches or wheelchairs or even resort to crawling on their knees to avoid increased plantar pain by walking. Utilizing ultrasound linages, researchers have recently captured images of the

Pachyonychia Congenita Overview The inherited nail dystrophy is associated with painful plantar keratoderma.

IWRY E. SCHWARTZ, LLD, C. DAVID HANSEN, MD, AMY S. PALLER, MD, FRANCES J. D. SMITH, PHD, AND ELI SPRECHER, MD, PHD

36 April 2014 I THE DERMATOLOGllTo I www.the-dermatolog ist. com

Pachyonychia congenita (PC) is a rare skin disorder caused by mutations affecting a group of keratins

found in specific regions of the epidermis. Although originally classified as a nail dystrophy, its major impact on adult pati ents is from painful plantar keratoderma . Other manifestations also commonly occur. This article reviews the clinical presentation, genetic diagnosis, pathogenesis and current and future treatment op tions for Pc.

CLINICAL PRESENTATION D ata gathered by the International

PC Research Registry (IPCRR) on more than 600 individuals with genetically confirmed PC show that PC always includes at least 1 other feature along with nail dystrophy. I

The most debilitating condition for those with PC is exquisitely painful plantar keratoderma. In some cases, this is the predorninant clinical presentation ' with little or no nail dystrophy.2.3 Other conunon manifestations of PC are extensive cysts including steatocysts, leukokeratosis, follicular hyperkeratosis and palmar keratoderma (Figures 1-7).1 However, only thickened nails may be evident in neonates and infants with pc. 4 N atal teeth may also be present at birth, predominantly in one PC subtype.

Leukokeratosis is another finding for PC infants and is often misdiagnosed and treated as thrush. Although florid leukokeratosis has often been incriminated as the cause of difficulty in feeding during infancy, especially with laryngeal involvement, an alternative underlying cause is a painful "first bite syndrome" experienced by some PC children. This is being assessed in a series of unpublished cases in the IPCRR. In each of these patients, a change to soft nipples with large holes immediately resolved the feeding problem.

Blisters or callus on the feet usually begin when a child with PC first begins to walk and the age of onset of plan tar keratoderma is a function of the extent of weight on the feet. T he pain is usually constant by age 10.4 Many adults with PC rely on canes, crutches or wheelchairs or even resort to crawling on their knees to avoid increased plantar pain by walking. Utilizing ultrasound images, researchers have recently captured images of the

underlying plantar blisters in PC patients. T hese are not found in other asymptomatic calluses of patients witll other conditions that have a similar appearance. This study has contributed to our understanding of the source of the incessant pain associated with PC plantar keratoderma s

From age 4 to 14 years, children with PC may experience extensive follicular hyperkera tosis especially in areas of friction aro und the waist, knees and elbows. In some types of PC, cysts are the dominant feature, characterized by milia in infa ncy and childhood and extensive body cysts at puberty continuing throughout adult life.

PATHOGENESIS Keratins are structural proteins that

promote the integrity of epithelial cells. As a result mutations in the genes encoding keratins lead to cell fragility6.7 The skin expresses the largest number of keratin genes of any organ. Widely distributed lesions in keratin disorders, as occurs in epidermolysis bullosa simplex, result £i.-om mutations in genes expressed throughout the epidermis. P C is caused by mutations in 5 keratin genes KRT6a , KRT6b, KRT6c, KRT16 and KRT1 7 w hich are expressed only in palmoplantar skin, the nail bed, pilosebaceous unit and oral mucosa, leading to selective involvement of these sites in pc. 3.7.8

GENETIC DIAGNOSIS PC is an autosomal-dominant disor

der, which has been reported worlwide with approximately equal prevalence in males and females. M ore than 45% of cases appear spontaneously with no fa mily history of pc. I Given the overlapping clinical presentation with other genetic disorders, only genetic testing can confirm the P C diagnosis.

With nearly 100 distinct PC mutations now identified , correlating the signs of PC with specific mutations and geiles has led to a new classification system of p c. While in the past, PC has been classified according to pheno typic features into PC-l and PC-2, the disorder is now classified into 5 subgro ups corresponding to the underlying genetic defect: PC-K6a, PC-K6b, PC-K6c,PC-K16 and PC-K17 .'·

8

As treatment development is focused on specific genes and mutations, free ge-

PACHYONYCHIA CONGENITA OVERVIEW

Figures 1-7. Typical characteristics of pachyonychia congenita include (0) facial cysts (b and c) plantar keratoderma (d) leukokeratosis (e) follicular hyperkeratosis (I) fingernail dystrophy (g) toenail dystrophy.

Apri.1 2014 I THE DERMATOLOGllTo I www.the-dermatologist.com . 37

PACHYONYCHIA CONGENITA OVERVIEW

netic testing is provided to each patient through the IPCRR sponsored by the PC Project (www.pachyonychia.org). Genetic testing not only confirms diagnosis but also aids genetic counseling.

TREATMENT Currendy there is no specific therapy

for PC so the main aim of treatment is to alleviate the pain caused by the plantar keratoderma. M echanical methods to remove the callus are most effective.9 The " not too thick, not too thin" motto is essential in caring for keratoderma. Bleach baths can reduce the onset of infections.

Many conUl10n treatments recommended by dermatologists (such as urea or salicylic acid- based emollients) are not useful in managing the PC kerato-

In a clinical trial, inj ection into plantar skin of a small intelfering RNA (siRNA) that specifically suppressed mutant KRT6a reduced the keratoderma at the inj ection site.12 H owever, the pain of treatment highlighted the need for alternative delivery methods particularly because such trea tment requires regular application to sustain the clinical result .

A clinica l trial of KRT6a siRNA, delivered by micro needles, is undergoin g regulatory approval. R apa mycin has been shown to inhibit the translation of K6a mRNA but has significant toxicity in its o ral fo rmuIation. 13 A trial o f topically-applied rapamycin fo r the plantar keratoderma is under way.

Currently there is no specific therapy for PC so the main aim of treatment is to alleviate the pain caused by th~ plantar keratoderma. Mechanical methods to remove the callus are most effective. The "not too thick, not too thin" motto is essential in caring for keratoderma. Bleach baths can reduce the onset of infections.

derma and al:e inferior to at least weekly trinmling in most types of Pc. Retinoid treatments, effective fo r some of the other keratin disorders, are also ineffective for PC plantar keratoderma and may increase pain .lo Mechanical treatment for nails is also favored and surgical removal of cysts is often required.9

An important aspect of patient ca re is recognizing the feelin g of isolation associated with this rare and highly visible skin disorder. Encouraging patients to becom e part of the IPCRR can provide tremendous emotional support because it connec ts them with others w ho understand the pain of PC and the functional and psychological affect of the diso rder. II This can be especially important for patients who have no other affected fa mily members.

More effective treatments are under investigation in preclinical and clinical trials. Physician members of the International PC Consortium (IPCC) have access to the latest PC research results and w ill be invaluable partners for PC patients as therapies are emerging and clinical trials results become available.

CONClUSION PC is a rare genetic diso rder for

w hich there are very few therapeutic options. By building a patient community through the IPCR..R and a physician and researcher community through the IPCC, PC Project is moving research forward to better understand the condition and to develop effe ctive trea tments.

Working alone, a single patient or physician canno t solve the qu estions of a rare disease. Sinlilarly experimental tr ials on individual pati ents w ill no t yield the data l:equired to set standards of practi ce to provide effec tive treatment to aU P C patients. Only by working together can we make ~ differenc e.We invite all patients, resea rchers and dermatologists to j oin w ith us in a cooperative effort to make progress in finding effective trea tments for this pa inful condition . •

Mary Schwartz is director if Pachyonychia Congenita Project in Salt Lake CitJ\ UT

D,: Hansen is a dermatologist at the University if Utah in Salt Lake Cit)\ UT

38 April 2014 I THE DERMATOLOGIIT' I www.the-dermatol?g isl.com

Dr. Paller is a pediatric dermatologist at Northwestern University in Chicago} IL.

Dr. Smith is a senior research fe llow at the University if Dundee in Dllndee} Scotland.

Dr. Sprecher is director if the dermatology departlnent at TeIAviv SoU/'asky Medical Centre in Tel Aviv, Israel.

Disclosure: The authors report no relevant financial relationships.

References 1. Eliason MJ, Leachman SA, Feng BJ, Schwartz ME, Hansen Co. A review of the cl inical phenotype of 254 patients with genetically confirmed pachyonychia congenita. ) A lii Acad Derlllatol. 2012;67(4) :680-686. 2. Smith FJ , Fisher MP, Healy E, et a!. Novel keratin 16 mutations and protein expression studies in pachyonyc hia congeni ta type 1 and focal paLnoplantar keratoderma. Exp Derlllato/. 2000;9(3): 170-177. 3. Wilson NJ, Messenger AG, Leachman SA, et a!. Keratin K6c mutations cause foca l palmoplantar keratoderma. ) il lIJest Derlllato /. 2010; 130(2) :425-4299 .

4. Shah S, Boen M, Kenner-Bell B, Schwartz M, Rademaker A, Paller AS. Pachyonyc hia congenita in pediatric patients: natural history, features, and impact.jAJ\.1A Derlllato/. 2014;150(2): 145-153. 5. Goldberg I, Sprecher E, Schwa rtz ME, Gaitini 0. Comparative study of high- resolution multi frequency ultrasound of the plantar skin in patients with various types of hereditary palmoplantar keratoderma. Derlllatology. 2013;226(4):365-370. 6. Coulombe PA, Lee C H . Defining keratin protein fun ction in skin ep ithelia: epidermolysis bullosa simplex and its aftermath.) fl lIJest Derlllatol. 2012;132(3 Pt 2):763-775. 7. McLean WH, Hansen CD, Eli ason MJ, Smith FJ. The phenotypic and molecular genetic features of pachyonychia congeni ta.) It west Derlllatol. 20 11 ;131(5):1015-10 17. 8. Wilson NJ, Leachman SA, Hansen CD, et a!. A large mu tational study in pachyonychia congenita. ) It llJest Denl/otol. 2011;13 J (5):1018-1024. 9. Goldberg I, Fruchter 0 , Meilick A, Schwartz ME, Sprecher E . Best treatment practices for pachyonychia congenita.j Ellr Acad Denl/otol Vel/ereol.2014;28(3) :279-285.

10. Gruber R , Edlinger M , Kaspar R.L, et al. An appra isal of oral retinoids in the trea tment of pachyonychia congenita . ) A lii Acad Derlllotol. 2012;66(6):eI 93-eI99. 11 . Schwartz ME, Z inunerman GM, Smith FJ, Sprecher E. Pac hyo nchia Congenita Project: a partnership of patient and medical professional.) Derlllatol N ll rses} Assoc. 2013;5(,1 ):42-47 . 12. Leachman SA, Hickerson RP, Schwartz ME, et a!. First-in- human mutation-ta rgeted siRNA phase Ib trial of an inherited ski n disorder. Mol Ther. 2010;18(2):442-446.

13. Hickerson RP, Leake D, Pho LN, Leachman SA, Kaspar R.L. Rapamycin selectively inhibits expression of an inducible keratin (K6a) in human keratinocytes and improves symptoms in

pachyo nychia congenita patients. ) Derlllotol Sci. 2009;56(2) :82-88.

Pachyonychia Congenita in Pediatric PatientsNatural History, Features, and ImpactSonal Shah, MD; Monica Boen, MD; Brandi Kenner-Bell, MD; Mary Schwartz, PhD; Alfred Rademaker, PhD;Amy S. Paller, MD

IMPORTANCE Nail dystrophy in early childhood often suggests a diagnosis of pachyonychiacongenita (PC). No previous investigation has focused on the early signs of PC and the naturalcourse of the disease.

OBJECTIVES To determine the course of pediatric PC, correlate the disease course with theclinical appearance and specific gene mutations, and assess the effect of pediatric PC onquality of life.

DESIGN, SETTING, AND PARTICIPANTS One hundred one patients or families with geneticallyconfirmed PC from the International Pachyonychia Congenita Research Registry whocompleted a survey on the general clinical features of PC and an auxiliary questionnaire onthe clinical presentation and quality-of-life issues related to pediatric PC.

EXPOSURE Individuals with pachyonychia congenita.

MAIN OUTCOMES AND MEASURES Completion of both surveys.

RESULTS At birth, toenail changes were present in 47.5% of patients; fingernail changes in40.6%; and plantar keratoderma in 6.9%. By 5 years of age, these 3 key manifestations werefound in 81.2%, 74.2%, and 75.3%, respectively, of individuals with genotype-confirmed PC.The correct diagnosis was made during the first year of life in 26.7% of patients despite thepresence of toenail dystrophy in more than 65.3%. Clinical differences that distinguished PCsubtypes included (1) later onset and less frequent occurrence of nail dystrophy andkeratoderma in PC-K6b, PC-K6c, and PC-K16; (2) concurrent fingernail and toenail thickeningin PC-K6a and PC-K17; (3) more palmar keratoderma in PC-K16; (4) cysts primarily in PC-K17and follicular hyperkeratoses primarily in PC-K6a; (5) hoarseness and/or oral leukokeratosesin the first year of life most often in PC-K6a; and (6) natal teeth exclusively in PC-K17. Amongpediatric patients, PC affected the social interactions and function of adolescents mostprofoundly.

CONCLUSIONS AND RELEVANCE Among patients with a detectable mutation, PC manifestswith nail thickening and plantar keratoderma before school age in more than three-quartersof affected children, allowing early diagnosis. The highly visible nail changes and painfulplantar thickening exert a psychosocial effect on most affected adolescents.Phenotype-genotype correlations in children with PC validate the new classification based onthe affected gene.

JAMA Dermatol. doi:10.1001/jamadermatol.2013.6448Published online October 16, 2013.

Supplemental content atjamadermatology.com

Author Affiliations: Department ofDermatology, NorthwesternUniversity Feinberg School ofMedicine, Chicago, Illinois (Shah,Boen, Kenner-Bell, Paller);Department of Pediatrics,Northwestern University FeinbergSchool of Medicine, Chicago, Illinois(Kenner-Bell, Paller); PachyonychiaCongenita Project, Salt Lake City,Utah (Schwartz); Department ofPreventive Medicine, NorthwesternUniversity Feinberg School ofMedicine, Chicago, Illinois(Rademaker).

Corresponding Author: Amy S.Paller, MD, Department ofDermatology, NorthwesternUniversity Feinberg School ofMedicine, 676 N St Clair, Ste 1600,Chicago, IL 60611 ([email protected]).

Research

Original Investigation

E1

Downloaded From: http://archderm.jamanetwork.com/ by a University of Utah User on 10/28/2013

P achyonychia congenita (PC) constitutes a group of al-most exclusively autosomal dominant disorders ofpaired keratins of the nails and skin. Since PC was ini-

tially reported in 1906 by Jadassohn and Lewandowsky,1 morethan 500 cases have been registered or otherwise described.Pachyonychia congenita manifests as nail dystrophy, painfulfocal palmoplantar keratoderma, follicular keratoses, muco-sal leukokeratoses, hoarse voice, cystic lesions, and, rarely, na-tal teeth.2,3

Underlying keratin gene mutations have been described inthe 5 keratin genes, KRT6A (OMIM 148041), KRT6B (OMIM148042), KRT6C (OMIM 612315), KRT16 (OMIM 148067), andKRT17 (OMIM 148069), which alter keratins 6a, 6b, 6c, 16, and17, respectively.4-9 These genes are expressed in the nail bed,palmoplantar epidermis, and mucosa. Keratins play a key rolein epidermal cell integrity and mechanical strength. Muta-tions in these 5 keratin genes cause epidermolysis and com-pensatory hyperkeratosis at these sites. Historically, 2 major sub-types were based on clinical characteristics. The Jadassohn-Lewandowsky PC type 1 (PC-1) often showed associated oralleukokeratoses,1 and the Jackson-Lawler PC type 2 (PC-2) of-ten showed cysts and occasionally natal teeth.3,10 Pachyo-nychia congenita type 1 was originally linked to mutations in thetype II keratin gene KRT6A and its type I expression partnerKRT16 and PC-2 with mutations in KRT6B and KRT17.3,4,6,8,11

Pachyonychia congenita has been genotyped at no cost inindividuals who enroll in an international registry, enablingcomprehensive genotype-phenotype analysis.12-16 Pheno-typic overlap among PC genotypes has now made obsolete thedesignations of PC-1 and PC-2. Instead, a new classificationbased on mutations in the keratin-encoding genes KRT6A,KRT6B, KRT6C, KRT16, and KRT17 divides PC into subtypesPC-K6a, PC-K6b, PC-K6c, PC-K16, and PC-K17, respectively.16

Features of PC usually manifest during the first 3 years oflife,12 allowing the diagnosis to be considered. However, littleattention has been paid to the disease course, early diagnos-tic features, and effect on quality of life of PC in children. Tofacilitate early diagnosis and increase our understanding aboutthe impact of PC in children, affected families and patients werepolled about pediatric-specific issues.

MethodsTwo questionnaires were administered to families participat-ing in the International Pachyonychia Congenita Research Reg-istry (IPCRR) through the Pachyonychia Congenita Project (ww-w.pachyonychia.org). The study and questionnaires wereapproved by Western Institutional Review Board (WIRB Studynumber 1057496; protocol number 20040468). The first ques-tionnaire asked general questions about PC features, their ef-fect on daily life, and interventions after registry enrollment12

(Supplement [eAppendix]). The diagnosis of PC was con-firmed by dermatologists from the Pachyonychia CongenitaProject medical and scientific advisory board through assess-ing family-provided questionnaire data, photographs of skinand nail changes, and a 1-hour patient/family telephone con-sultation.

An auxiliary 48-question survey (approved by the IRB at Annand Robert H. Lurie Children’s Hospital of Chicago) was sent bythe Pachyonychia Congenita Project to 254 registry families withgenotype-confirmed PC (Supplement [Appendix]) and ad-dressed pediatric-specific issues, early signs, and the natural his-tory of PC. Parents completed the survey for preteenaged pa-tients with input from children as appropriate; patients of all ageswere encouraged to consult with their parents to answer ques-tions related to the disorder early in life. Informed consent wasobtained from all participants. The results of both question-naires were sent to the Pachyonychia Congenita Project, whichsorted data by keratin mutation and provided de-identified datafor compilation and statistical analysis at Northwestern Uni-versity. We performed Fisher exact testing to determine statis-tical significance (defined as P < .05) in comparing clinical fea-tures with underlying keratin gene mutations. All statisticalanalyses were performed with commercially available soft-ware (SPSS, version 15.0 [SPSS Inc], and Stata, version 10.0[StataCorp]). Because PC-K6c was first termed PC after the aux-iliary questionnaire was introduced (2012), only data from thefirst questionnaire were available from patients with this sub-type. Given its mild clinical features, PC-K6c was excluded instatistical analyses to distinguish among PC subtypes. Data fromindividuals with mutations in the GJB6 gene (OMIM 604418),also known as connexin 30, were derived from the originalquestionnaire.

ResultsOf 254 patients enrolled in the IPCRR who completed the origi-nal questionnaire and had genetically confirmed PC, 101 re-sponded to the addendum questionnaire (response rate, 39.8%).The demographic features of these 101 PC patients and the 8 PC-K6c patients who responded to the original questionnaire aredescribed in Table 1. Of the returned questionnaires, 78.0% werecompleted by adult patients who were able to report the onsetof features and impact of PC throughout the first 18 years of life,whereas 22.0% of the returned questionnaires reflected the ex-perience to date of affected individuals currently in their first 2decades of life. Among the respondents, 42.2% had mutationsin KRT6A (PC-K6a), and an additional 28.4% had mutations inKRT16 (PC-K16). Almost 60% in the registry had a family his-tory of PC, reflecting the high rate of spontaneous mutation inkeratin genes. The diagnosis of PC by a physician was made be-fore 1 year of age in 27 patients (26.7%, of whom 12 [44.4%] hada known family history) despite the presence of toenail and fin-gernail dystrophy in approximately 60% of the affected in-fants (see below). By 5 years of age, the correct diagnosis wasmade in 43 patients (42.6%, of whom 18 [41.9%] had a knownfamily history) despite toenail dystrophy in 81% (82 of 101), fin-gernail dystrophy in 74% (75 of 101), and plantar keratodermain 75% (76 of 101).

Toenail DystrophyThe earliest and most common clinical characteristic of PC wastoenail dystrophy (Figure 1A), noted to involve at least 2 dig-its in 98.2% of patients by the time of reporting; the only ex-

Research Original Investigation Pachyonychia Congenita in Pediatric Patients

E2 JAMA Dermatology Published online October 16, 2013 jamadermatology.com


ception was absence of toenail dystrophy in 2 of the 8 PC-K6cpatients (25.0%) (Table 1). Of the patients with toenail involve-ment, all 10 toenails were affected in 74.3%, 98.0% had in-volvement of toenails of the fifth digit, and 98.0% had changesof the hallucal nails by the time of reporting. Toenail abnor-malities were present at birth in 39.0% of respondents over-all, although they appeared most often in neonates with PC-K6a and PC-K17 (P < .001) (Supplement [eFigure, A]). By 1 and5 years of age, nail dystrophy was noted in 65.3% and 80.2%of all respondents, respectively. By 5 years of age, all 46 chil-dren with PC-K6a, the most common subset, showed toenailchanges. In contrast, toenail changes did not appear in chil-dren with PC-K6b until at least 1 year of age and progressivelyincreased in occurrence thereafter. In 99.0% of patients withtoenail dystrophy, more than 1 nail became dystrophic con-currently, and 70.3% had all 10 nails become dystrophic at the

same time; patients with PC-K6a were more likely to have all10 toenails affected at onset than were patients with PC-K16or PC-K6b (P < .001). The hallucal nail was the most commonof the toenails to first become affected (89.1% of PC patientswith toenail dystrophy). The most common initial toenailchange was thickening (77.2% of all patients), and 65.3% alsoshowed toenail discoloration at onset. Toenail thickening pro-gressed throughout the first decade of life in most of the pa-tients. The nail dystrophy occurred before 6 years of age in 5of the 6 PC-K6c patients with this feature (83.3%), but the dys-trophy was mild, affecting only 1 toenail bilaterally (usually thefifth toenail) or, in 1 case, multiple toenails unilaterally. The 2PC-K6c patients without nail involvement were adults.

Fingernail changes occurred overall in 76.1% of patientsand, as with toenail changes, were most severe in PC-K6a. Over-all, 40.6% of patients had fingernail changes at birth. Finger-

Table 1. Demographics of Registry Patients and Distinguishing Clinical Features Among PC Subtypesa

Feature

All(N = 109

[100.0%])b

PC Subtype

P Valuec

PC-K6a(n = 46

[42.2%])

PC-K6b(n = 10[9.2%])

PC-K6c(n = 8

[7.3%])

PC-K16(n = 31

[28.4%])

PC-K17(n = 14

[12.8%])Demographic

Current age, y

Mean (SD) 36.0 (19.9) 32.4 36.1 37.6 43.6 30.1>.05

Median (range) 35.5 (0-81) 33 41 44 43 27

Age group, y (0-63 y) (9-54 y) (6-72 y) (1-81 y) (3-68 y)

0-5 9 (8.3) 5 (10.9) 0 0 1 (3.2) 3 (21.4)

6-10 8 (7.3) 4 (8.7) 1 (10.0) 2 (25.0) 0 1 (7.1)

11-17 7 (6.4) 2 (4.3) 1 (10.0) 0 3 (9.7) 1 (7.1)

≥18 85 (78.0) 35 (76.1) 8 (80.0) 6 (75.0) 27 (87.1) 9 (64.3)

Sex

Female 61 (56.0) 26 (56.5) 2 (20.0) 5 (62.5) 17 (54.8) 11 (78.6)>.05

Male 48 (44.0) 20 (43.5) 8 (80.0) 3 (37.5) 14 (45.2) 3 (21.4)

Family history positive for PC 65 (59.6) 21 (45.7) 8 (80.0) 8 (100.0) 20 (64.5) 8 (57.1) >.05

Keratin gene mutation KRT6A KRT6B KRT6C KRT16 KRT17 >.05

Clinical

Dystrophy

Toenail 107 (98.2) 46 (100.0) 10 (100.0) 6 (75.0) 31 (100.0) 14 (100.0) >.05

Fingernail 84 (77.1) 46 (100.0) 4 (40.0) 0 21 (67.7) 13 (92.9) <.001

Keratoderma

Plantar 107 (98.2) 45 (97.8) 10 (100.0) 8 (100.0) 31 (100.0) 13 (92.9) >.05

Palmar 47 (43.1) 17 (37.0) 4 (40.0) 0 21 (67.7) 5 (35.7) <.05

Paind

Plantar 100 (91.7) 43 (93.5) 10 (100.0) 8 (100.0) 30 (96.8) 9 (64.3) <.05

Palmar 23 (21.1) 11 (23.9) 1 (10.0) 0 9 (29.0) 2 (14.3) <.05

Oral leukokeratosis 81 (74.3) 45 (97.8) 4 (40.0) 0 17 (54.8) 5 (35.7) <.001

Cyst 71 (65.1) 41 (89.1) 7 (70.0) 1 (12.5) 9 (29.0) 13 (92.9) <.001

Follicular hyperkeratosis 54 (49.5) 37 (80.4) 6 (60.0) 0 4 (12.9) 7 (50.0) <.001

Natal teeth 14 (12.8) 2 (4.3) 0 0 0 12 (85.7) <.001

Hoarseness 17 (15.6) 14 (30.4) 0 0 1 (3.2) 2 (14.3) <.05

Abbreviation: PC, pachyonychia congenita.a Unless otherwise indicated, data are expressed as number (percentage) of

patients. Percentages have been rounded and may not total 100.b Includes the 101 patients who responded to both questionnaires and the 8

PC-K6c patients who responded to the original questionnaire only.

c Statistical analysis compares subtypes PC-K6a, PC-K6b, PC-K16, and PK-17.P < .05 indicates statistical significance.

d Indicates percentages with pain among patients with plantar or palmarkeratoderma.

Pachyonychia Congenita in Pediatric Patients Original Investigation Research

jamadermatology.com JAMA Dermatology Published online October 16, 2013 E3


nail involvement occurred in most of the neonates with PC-K6a and PC-K17 but infrequently in neonates with PC-K16 andnever in neonates with PC-K6b (P < .001) (Supplement [eFig-ure, B]). Fingernail changes never developed in 5 patients withPC-K6b (50.0%), 11 patients with PC-K16 (35.5%), 1 patient withPC-K17 (7.1%), and the 8 patients with PC-K6c (100.0%). By 5years of age, all children with PC-K6a and 13 children with PC-K17 (92.9%) showed fingernail dystrophy, in addition to toe-nail dystrophy. Fingernail dystrophy developed simultane-ously in all 10 nails in 68.7% of PC patients; only 6.0% reportedinvolvement in only 1 nail, with no consistency as to the in-volved digit. The initial change in fingernails was nail thick-ening in 65 of the 86 patients with nail changes (75.6%), usu-ally in combination with changes in color (41 [63.1%]). All

patients with fingernail dystrophy, regardless of PC subtype,had toenail involvement. However, patients with PC-K6a andPC-K17 were more likely to develop dystrophy of their finger-nails and toenails concurrently, whereas patients with PC-K6b and PC-K16 were more likely than other subtypes to de-velop toenail dystrophy first (P < .001).

The toenails and fingernail dystrophy varied in appear-ance from thickened, shortened, friable nails to nails withmarked subungual thickening and a typical pinched, V-shaped curvature (Figure 1A and B). We found no correlationbetween the appearance of the nails and the PC subtype.

Periungual infections occurred in 76.6% of PC patientsoverall but more often in those with PC-K6a (43 of 46 [93.5%])than those with other subtypes (P < .05). Most patients with

Figure 1. Representative Images of Clinical Features of Pachyonychia Congenita and Genotype in AffectedChildren

AA B

C D

E F G

A. Subungual hyperkeratosis andV-shaped thickening of the toenails ina toddler with a KRT17 M88Kmutation. B. Discolored andthickened distal aspect of allfingernails owing to a KRT16 R127Pmutation. C, Severe plantarkeratoderma in a child with a KRT16S130del mutation. D, Mild plantarkeratoderma in a child with a KRT6CE472K mutation. E, Oralleukokeratosis of the tongue in aninfant with a KRT6A L468P mutation.Leukokeratosis was misdiagnosedinitially as a candidal infection. F, Oralleukokeratoses of the tongue in anadolescent with a KRT6A N172delmutation. G, Follicular keratoses onthe knee owing to a KRT6A N172delmutation.




nail infections (52 of 73 [71.2%]) never sought treatment by aphysician. Most of these patients treated nails by soaking them(38 of 61 [62.3%]), lancing purulent areas or trimming the nails(35 of 61 [57.4%]), or using topical medication (28 of 61 [45.9%]).Nail infection or its clearance did not lead to a change in ap-pearance of the dystrophic nail.

Painful Plantar KeratodermaThe feature of PC that has the most profound effect on qual-ity of life is painful plantar keratoderma (Figure 1C and D).12

Although present at birth in fewer than 10% of individuals withPC, 24.8% of PC patients overall noted plantar keratoderma by1 year of age, 75.3% by 5 years of age, and 89.1% within the firstdecade of life (Supplement [eFigure, C]). Of the 27 patients di-agnosed with PC before 1 year of age, 12 (44.4%) had plantarkeratoderma by the time of diagnosis. In patients with PC-K6a, PC-K16, and PC-K17, the onset of plantar keratoderma usu-ally occurred before age 5 years, whereas in patients with PC-K6b and PC-K6c, onset was usually after age 5 years. The mostcommon initial locations of the plantar keratoderma were atpressure points on the heel (66 of 98 [67.3%]) and ball (63 of98 [64.3%]) of the foot. During the first decade of life, 70 ofthe 73 patients with keratoderma (95.9%) had plantar pain,which compromised their function; pain occurred later in chil-dren with PC-K6b than the other subtypes (P < .05). Most pa-tients with plantar keratoderma also had local skin infections(47 of 99 [47.5%]).

Palmar keratoderma occurred in only 45.5% of patientsoverall by the time of the response to the questionnaire. Ofthose who developed palmar keratoderma, 24 of 47 (51.1%) sawchanges by 5 years of age, and 32 of 47 (68.1%) by 10 years(Supplement [eFigure, D]). Palmar keratoderma was more of-ten reported in PC-K16 than in any other subtype (67.7%;P < .05) and was often complicated by painful erosions, bul-lae, or fissures of the palms, usually before 5 years of age.

Other Clinical ManifestationsAlthough PC-K6b and PC-K6c were often distinguishable fromother forms because of their more limited manifestations, fea-tures other than nail dystrophy and keratoderma were help-ful in differentiating among the PC-K6a, PC-16, and PC-17 sub-types in children. In particular, oral leukoplasia, cysts, andkeratoses varied by PC subtype.

Oral LeukokeratosesThe oral leukokeratoses occurred in 70.3% of PC patients andwere more strongly associated with PC-K6a than with any othersubtype (P < .001). Of those affected, the median age at onsetwas 3 weeks, and 26 of 71 (36.6%) experienced a first occur-rence during the first year of life. Oral leukokeratoses were of-ten mistaken for thrush (Figure 1E) but failed to respond to an-ticandidal therapy. Oral leukokeratoses were most commonlynoted on the tongue (Figure 1E and F) (68 of 71 [95.8%]).Hoarseness was noted in 12.9% of patients overall, and PC-K6a patients were more likely to develop hoarseness than PC-K6b and PC-K16 patients (P < .05) but not PC-K17 patients. Theonset of hoarseness was variable but always present before 3years of age in the affected patients. Of the PC patients who

developed hoarseness, 16 (93.3%) concurrently showed oralleukokeratoses. Natal teeth virtually clinched the diagnosisof PC-K17 (86.0% [P < .001]) but were noted in 2 of 46 infants(4.3%) of infants with PC-K6a. The teeth were described assoft or crumbly and were rapidly lost or were described asnormal in appearance and persistent until the deciduousteeth erupted.

CystsCysts were noted overall in 69.3% of patients with PC. Mostpatients who developed cysts had PC-K6a, PC-K6b, or PC-K17, without a statistically significant difference in the risk fordeveloping cysts among these subgroups. Patients with the PC-K16 subtype were the least likely to develop cysts (P < .05), andcysts did not develop in PC-K6c patients. The onset of cystsoccurred most often from 6 to 10 (31.6%) and 11 to 20 (36.8%)years of age. Patients primarily treated their cysts by lancingthem (37 of 54 [68.5%]) or applying topical antibiotic oint-ment (26 of 54 [48.1%]).

Follicular Hyperkeratoses and HyperhidrosisFollicular hyperkeratoses were described in more than half ofthe PC patients, although only in 26 (25.7%) by preschool age(Figure 1G). They occurred most often in PC-K6a (80.4%) andPC-K6b (42.9%) and least commonly in PC-K16 (12.9%; P < .001compared with PC-K6a). In patients with PC-K6a, 14 of 37(37.8%) developed cysts at 1 to 5 years of age and 23 of 37 (62.1%)showed follicular hyperkeratoses by the second decade of life(Supplement [eFigure, E]). Only 1 PC-K16 patient developedfollicular hyperkeratoses during childhood, and 27 of 31 pa-tients with PC-K16 (87.1%) never developed follicular hyper-keratoses by the time of reporting. Hyperhidrosis was de-scribed in 51.5% of respondents of all ages, but in only 5 of 22children (22.7%). Alopecia was not an issue in children withPC in the first decade of life, and its association with PC is ques-tionable. In the original survey of 254 PC patients, 15 patientsranging in age from 15 to 81 years had hair loss. Of these pa-tients, 10 were male and most had no other hair abnormality,raising the question of androgenic alopecia as the cause. Allbut 1 of these individuals had PC-K6a or PC-K16.

Effect on Quality of Life in AdolescentsPlantar keratoderma in PC was characteristically painful by thesecond decade of life and led to the greatest effect on qualityof life. More than 50% of children found that the plantar kera-toderma affected walking and playtime; however, less than halfof patients also found impedance with crawling, schoolwork,and chores (Figure 2A). The effect on function more often be-gan after 5 years of age, peaked during adolescence, and oc-curred most often with PC-K6a. Pachyonychia congenita af-fected the social life of virtually all patients of school age orolder. Most experienced limitations related to wearing clothesand playing sports (Figure 2A), experienced teasing, and wereembarrassed by their nails, especially during adolescence(Figure 2B and Table 2). Of the 84 PC patients with fingernailinvolvement, 66 (78.6%) concealed their nails, especially bykeeping the fingers curled (50 [59.5%]) or crossing the arms (46[54.8%]). Other techniques included keeping hands in the pock-




ets (31 [36.9%]), using nail polish (25 [29.8%]), using artificialnails (9 [10.7%]) and wearing gloves (7 [8.3%]).

PC-Like Early Nail Dystrophy and Connexin 30 MutationsOnly patients with gene-confirmed PC subsets completed thepediatric-specific questionnaire. However, among patients inthe original registry questionnaire, 7 with nail dystrophy andclinically presumed PC had mutations in the connexin 30 gene(GJB6) (Table 3). Of these, 5 (71.4%) had abnormalities of thetoenails and fingernails at birth, with the other 2 developingdystrophy of the fingernails and toenails concurrently at 2 and4 years of age. Two additional features found commonly with

connexin 30 mutations, but not PC, were hearing loss and alo-pecic patches or sparseness, with hair that was described asthin and sometimes brittle.

DiscussionPachyonychia congenita constitutes a group of primarily auto-somal dominant inherited disorders caused by mutations inpaired keratins. Genotyping has been provided since 2004 as aservice for families enrolled in the IPCRR and has yielded awealth of information about PC characteristics and genotype-

Figure 2. Functional Impairment and Extent of Embarrassment by Pachyonychia Congenita (PC) Subtype

0.0Crawling Walking Sports Playtime School Chores

Freq

uenc

y of

Impa

irmen

ta

Activities of Daily Life

1.5

1.0

0.5

PC-K6a

PC-K6b

PC-K16

PC-K17

A

2.0

2.5

0.01-5 6-10 11-20 21-30 >30

2.0

Mea

n Fr

eque

ncy

of E

mba

rras

smen

ta

Age Group, y

1.5

1.0

0.5

PC-K6a

PC-K6b

PC-K16

PC-K17

B

2.5

A, Effects of plantar or palmarkeratoderma on activities of daily life.B, Age at embarrassment about theappearance of nails. Given its mildclinical features, the PC-K6c subtypewas excluded from the analysis.aPatients or families gradedfrequency on a 4-point scale, where0 indicates never; 1, little effect; 2,moderate effect; and 3, always/worstburden.

Table 2. Effects of PC on Social Life of School-aged Children

EffectAll, No. (%)

(n = 92)

PC Subtype, No. (%) Reporting an Adverse Effect on Social Lifea

P ValuebPC-K6a(n = 41)

PC-K6b(n = 10)

PC-K16(n = 30)

PC-K17(n = 14)

Teasing 69 (75.0) 37 (90.2) 4 (40.0) 20 (66.7) 8 (72.7) <.01

Difficulty wearing certain clothes/accessories 79 (85.9) 36 (87.8) 5 (50.0) 29 (96.7) 9 (81.8) <.01

Difficulty participating in recreationalactivities

63 (68.5) 36 (87.8) 6 (60.0) 26 (86.7) 8 (72.7) .13

Dating problems 40 (43.5) 22 (52.6) 3 (33.3) 12 (40.0) 5 (45.5) .68

Abbreviation: PC, pachyonychia congenita.a None of the patients with PC-K6c reported an adverse effect on their social

life.

b Statistical analysis compares subtypes. P < .05 indicates statisticalsignificance.




phenotype correlations. By pooling data collected through theIPCRR questionnaire and an auxiliary questionnaire, we wereable to address the early features of PC in an effort to aid earlydiagnosis and bring attention to the profound effect this geno-dermatosis has on the quality of life of affected children and ado-lescents.

Our data confirm the frequent misdiagnosis of PC in pe-diatric patients, showing that most children manifest the keyfeatures in the first year of life, but the diagnosis is made inonly about 25%. This delay in diagnosis may lead to inappro-priate management (eg, topical or oral antifungals for pre-sumed fungal infection, potent topical corticosteroids for pre-sumed psoriasis) or incorrect information about prognosis andinheritance (eg, mistaking hidrotic ectodermal dysplasia withconnexin 30 mutations for PC). The unifying feature of PC isnail dystrophy,17 although the clinical appearance of nails canbe variable, even within families, and does not always showthe classic V-shaped thickening. During the first year of life,dystrophy of the fingernails and toenails occurs in most of the

affected infants, providing an initial clue. By 5 years of age,plantar keratoderma is seen in 75.3% of children in additionto the nail dystrophy and is often painful. Thus, the diagnosisof PC should easily be suspected before kindergarten. Al-though genotyping should be performed through the registryto subclassify the disease, the combination of data about ageat onset, concurrent dystrophy of fingernails and toenails, pal-mar keratoderma, and the presence of oral leukokeratosisand/or hoarseness, cysts, follicular keratoses, and natal teethhelps the practitioner to suspect a specific PC subtype andcounsel families, even before genotyping is completed. For ex-ample, the presence of nail dystrophy at birth, especially in-volving all nails, predicts PC-K6a or PC-K17 (P < .001); the con-comitant development of oral leukokeratosis and oftenhoarseness during the first year of life suggest the diagnosisof PC-K6a (P < .001); and the concurrence of natal teeth indi-cates PC-K17 (P < .001). In contrast, the development duringchildhood of palmar keratoderma, especially with later onsetof other features, may signal PC-K16. The presence of an iso-lated dystrophic fingernail or toenail is quite uncommon in PC(77 patients with fingernail involvement overall and 6 [5.5%]with only 1 fingernail involved; 106 with toenail involvementand 1 with only 1 toenail involved [0.9%]); the exception is PC-K6c, in which localized nail involvement is common.18,19

These features, although helping to differentiate amongthe PC subtypes, also allow us to reject the old classifica-tions of PC-1 and PC-2 in pediatric PC. For example, cystsand natal teeth are most common in PC-K17 (formerly clas-sified as PC-2) but were both described in individuals withPC-K6a (formerly PC-1) in our pediatric cohort and otherpublished series.12,13 Hair disorders, at one time attributedto PC-2 KRT6B and KRT17 mutations, do not seem to beassociated with autosomal dominant PC more often than inthe general population. Alopecia has recently beendescribed in association with severe PC manifestations in apatient with homozygous dominant missense mutations(from each affected parent) in keratin 17.20 These data sup-port restructuring of the classification of PC from 2 differentsubtypes to a system that categorizes the disease based onspecific keratin mutations.12,16,21

As a keratinopathy, PC is associated with increased cellu-lar fragility and compensatory epidermal thickening at the sitesof gene expression (particularly plantar keratoderma and naildystrophy). The greater dystrophy of toenails vs fingernails andof the hallucal and fifth toenails likely reflect the propensitytoward more pathological features with trauma. Natal teeth,which occurred in 13.9% of patients with PC overall and 86%of patients with PC-K17, have similarly been described in epi-dermolysis bullosa simplex, which results from mutations inkeratins 5 or 14.22 The role of keratin abnormalities in tooth for-mation is poorly understood.

The genetic disorder that is most commonly confusedwith PC is hidrotic ectodermal dysplasia (Clouston syn-drome), which results from mutations in connexin 30. Fiveof the 7 individuals from 2 families with Clouston syndromewho were enrolled in the PC registry for genotyping alsoshowed multiple toenails and fingernails affected at birth,and several individuals developed painful plantar kerato-

Table 3. Demographics and PC-Like Clinical Characteristics of 7Participants With Mutations in the Connexin 30 Genea

Feature DataDemographic

Current age, y

Mean (SD) 48.3 (30.5)

Median (range) 37 (6-92)

Age group, y

0-5 0

6-10 1 (14.3)

11-17 0

≥18 6 (85.7)

Sex

Female 3 (42.9)

Male 4 (57.1)

Family history positive for PC 7 (100.0)

Clinical

Dystrophy

Toenail 7 (100.0)

Fingernail 7 (100.0)

Keratoderma

Plantar 3 (42.9)

Palmar 3 (42.9)

Pain

Plantar 2 (28.6)

Palmar 2 (28.6)

Hearing loss 3 (42.9)

Abnormal hair 4 (57.1)

Oral leukokeratoses 1 (14.3)

Cysts 1 (14.3)

Hyperhidrosis 2 (28.6)

Hypohidrosis 2 (28.6)

Learning disabilities 1 (14.3)

Abbreviation: PC, pachyonychia congenita.a Unless otherwise indicated, data are expressed as number (percentage) of

patients.




derma. However, the presence in hidrotic ectodermal dys-plasia of hearing loss (a common feature of connexin genedefects) and thin, sparse hair during childhood is not typicalof PC. Another genetic disorder with which PC could be con-fused results from mutation of FZD6. The FZD6 geneencodes frizzled 6, a Wnt-signaling pathway receptor that islocalized to the nail matrix; autosomal recessive mutationsin FZD6 lead to hypertrophic nail dystrophy from birthwithout plantar or palmar keratoderma.23,24

Our study emphasizes the negative effect of the nail andskin changes of PC in preteenaged and adolescent patients.Most patients reported embarrassment, teasing, an effect ondating, and limitations in participation in physical activitieswith classmates. Early diagnosis and discussion allow proac-tive management of psychosocial issues, including how a childcan comfortably inform peers about the disorder or how a teen-

ager can improve the appearance of nails and keratoderma,thus improving patient coping.

This study was limited by its retrospective nature, lead-ing to the risk of recall bias, particularly when inquiring aboutdisease characteristics at onset during the pediatric years giventhat most of the patients were well into their adult years whenthey responded to the questionnaire. Nevertheless, the datain this registry database show that PC can be diagnosed dur-ing early childhood based on the constellation of clinical fea-tures and genotyping. Genotyping is currently performed atno cost on a research basis (ie, not by a Clinical Laboratory Im-provement Amendment–approved laboratory) by registeringwith the IPCRR (www.pachyonychia.org). The many genotype-phenotype and subtype-phenotype correlations allow for earlyclassification, prediction of clinical features and their age atonset, and optimal management.

ARTICLE INFORMATION

Accepted for Publication: June 27, 2013.

Published Online: October 16, 2013.doi:10.1001/jamadermatol.2013.6448.

Author Contributions: Dr Paller had full access toall the data in the study and takes responsibility forthe integrity of the data and the accuracy of thedata analysis.Study concept and design: Kenner-Bell, Paller.Acquisition of data: Shah, Boen, Schwartz, Paller.Analysis and interpretation of data: Shah, Boen,Rademaker, Paller.Drafting of the manuscript: Shah, Boen, Schwartz,Paller.Critical revision of the manuscript for importantintellectual content: Shah, Boen, Kenner-Bell,Rademaker, Paller.Statistical analysis: Shah, Boen, Rademaker, Paller.Administrative, technical, and material support:Boen, Paller.Study supervision: Boen, Paller.

Conflict of Interest Disclosures: Dr Paller is amember of the International PachyonychiaCongenita Consortium without financialcompensation. No other disclosures were reported.

Funding/Support: The genotyping for the IPCRR isconducted under grant 315.811099 from thePachyonychia Congenita Project to the Universityof Dundee McLean/Smith laboratory.

Role of the Sponsor: The funders had no role in thedesign and conduct of the study; in the analysis,and interpretation of the data; or in thepreparation, review, or approval of the manuscript.The Pachyonychia Congenita Project assisted in thecollection of data for the manuscript.

Additional Contributions: Genotyping wasperformed in the laboratory of W. H. Irwin McLean,DSc, FRSE, and Frances J. D. Smith, PhD, Universityof Dundee, Scotland.

REFERENCES

1. Jadassohn J, Lewandowsky P. Pachyonychiacongenita: keratosis disseminata circumscripts(follicularis): tylomata: leukokeratosis linguae.Ikonographia Dermatol. 1906:29-31.

2. Irvine AD, McLean WH. Human keratin diseases.Br J Dermatol. 1999;140(5):815-828.

3. Leachman SA, Kaspar RL, Fleckman P, et al.Clinical and pathological features of pachyonychiacongenita. J Investig Dermatol Symp Proc.2005;10(1):3-17.

4. Bowden PE, Haley JL, Kansky A, Rothnagel JA,Jones DO, Turner RJ. Mutation of a type II keratingene (K6a) in pachyonychia congenita. Nat Genet.1995;10(3):363-365.

5. Cogulu O, Onay H, Aykut A, et al. Pachyonychiacongenita type 2, N92S mutation of keratin 17 gene.Eur J Pediatr. 2009;168(10):1269-1272.

6. Covello SP, Smith FJ, Sillevis Smitt JH, et al.Keratin 17 mutations cause either steatocystomamultiplex or pachyonychia congenita type 2. Br JDermatol. 1998;139(3):475-480.

7. McLean WH, Rugg EL, Lunny DP, et al. Keratin 16and keratin 17 mutations cause pachyonychiacongenita. Nat Genet. 1995;9(3):273-278.

8. Smith FJ, Jonkman MF, van Goor H, et al. Amutation in human keratin K6b produces aphenocopy of the K17 disorder pachyonychiacongenita type 2. Hum Mol Genet.1998;7(7):1143-1148.

9. Smith FJ, Liao H, Cassidy AJ, et al. The geneticbasis of pachyonychia congenita. J InvestigDermatol Symp Proc. 2005;10(1):21-30.

10. Clementi M, Cardin de Stefani E, Dei Rossi C,Avventi V, Tenconi R. Pachyonychia congenitaJackson-Lawler type. Br J Dermatol.1986;114(3):367-370.

11. Munro CS. Pachyonychia congenita. Br JDermatol. 2001;144(5):929-930.

12. Eliason MJ, Leachman SA, Feng BJ, SchwartzME, Hansen CD. A review of the clinical phenotypeof 254 patients with genetically confirmedpachyonychia congenita. J Am Acad Dermatol.2012;67(4):680-686.

13. Fu T, Leachman SA, Wilson NJ, Smith FJ,Schwartz ME, Tang JY. Genotype-phenotypecorrelations among pachyonychia congenitapatients with K16 mutations. J Invest Dermatol.2011;131(5):1025-1028.

14. McLean WH, Hansen CD, Eliason MJ, Smith FJ.The phenotypic and molecular genetic features ofpachyonychia congenita. J Invest Dermatol.2011;131(5):1015-1017.

15. McLean WH, Smith FJ, Cassidy AJ. Insights intogenotype-phenotype correlation in pachyonychiacongenita from the human intermediate filamentmutation database. J Investig Dermatol Symp Proc.2005;10(1):31-36.

16. Wilson NJ, Leachman SA, Hansen CD, et al. Alarge mutational study in pachyonychia congenita.J Invest Dermatol. 2011;131(5):1018-1024.

17. Ward KM, Cook-Bolden FE, Christiano AM,Celebi JT. Identification of a recurrent mutation inkeratin 6a in a patient with overlapping clinicalfeatures of pachyonychia congenita types 1 and 2.Clin Exp Dermatol. 2003;28(4):434-436.

18. Wilson NJ, Messenger AG, Leachman SA, et al.Keratin K6c mutations cause focal palmoplantarkeratoderma. J Invest Dermatol. 2010;130(2):425-429.

19. Akasaka E, Nakano H, Nakano A, et al. Diffuseand focal palmoplantar keratoderma can be causedby a keratin 6c mutation. Br J Dermatol.2011;165(6):1290-1292.

20. Wilson NJ, Pérez ML, Vahlquist A, et al.Homozygous dominant missense mutation inkeratin 17 leads to alopecia in addition to severepachyonychia congenita. J Invest Dermatol.2012;132(7):1921-1924.

21. Spaunhurst KM, Hogendorf AM, Smith FJ, et al.Pachyonychia congenita patients with mutations inKRT6A have more extensive disease compared withpatients who have mutations in KRT16. Br JDermatol. 2012;166(4):875-878.

22. Liu HH, Chen CJ, Miles DA. Epidermolysisbullosa simplex. ASDC J Dent Child.1998;65(5):349-353.

23. Naz G, Pasternack SM, Perrin C, et al. FZD6encoding the Wnt receptor frizzled 6 is mutated inautosomal-recessive nail dysplasia. Br J Dermatol.2012;166(5):1088-1094.

24. Perrin C, Langbein L, Schweizer J. Expressionof hair keratins in the adult nail unit. Br J Dermatol.2004;151(2):362-371.




Clinical dermatology • Original article CEDClinical and Experimental Dermatology

Can skin disease cause neuropathic pain? A study in pachyonychiacongenita

T. Wallis,1 C. D. Poole2 and B. Hoggart3

1University Hospitals Southampton, Southampton General Hospital, Southampton, Hampshire, UK; 2Department of Primary Care & Public Health, Cardiff

University, Cardiff, Glamorgan, UK; and 3Pain Management Research, Solihull Hospital, Heartlands NHS Foundation Trust, Solihull, UK

doi:10.1111/ced.12723

Summary Introduction. Pachyonychia congenita (PC) is a rare skin disorder caused by an

autosomal dominant mutation in one of five genes encoding keratin (K6a, K6b, K6c,

K16 or K17; each defining one PC subtype). Pain is a prominent symptom, but its

severity and type are poorly characterized.

Methods. In total, 35 genotyped US patients with PC consented to clinical assess-

ment including the quality of life (QoL) questionnaire EQ-5D-3L, the Brief Pain

Inventory (BPI) and painDETECT. Abbreviated quantitative sensory testing (QST)

was also performed, and included mechanical detection threshold (MDT), mechanical

pain threshold (MPT), wind-up pain ratio (WUR) and vibration detection threshold

(VDT).

Results. Significant pain in patients with PC was confirmed, as indicated by mean

BPI severity and interference of 4.2 � 1.7 and 4.4 � 2.2, respectively, as well as

QoL impairment, as indicated by mean EQ-5D index of 0.69 � 0.18. PD identified

neuropathic pain in 62% of patients, the remainder being nociceptive. The pain-

DETECT score was most significantly related to EQ-5D index (R2 = 0.26, P = 0.02).

The K17 and K6a subtypes exhibited significantly worse QoL (0.584 and 0.613

respectively) than the K16 and K6b subtypes (P = 0.02). In QST analysis, abnormal

pressure pain (assessed as MPT) was frequently observed, with more than half of

patients with PC affected (54%), and 57% of patients with K17 also exhibiting

abnormality in minimum touch threshold (assessed as MDT, P < 0.05). Very few

patients were receiving analgesic therapy appropriate for neuropathic pain.

Conclusion. Significant neuropathic pain was observed in PC, which warrants

appropriate treatment. The health states observed in this sample are at a level that

the average US citizen would forfeit one-third of their remaining lifespan to avoid.

Introduction

Pachyonychia congenita (PC) is a rare skin disorder

caused by an autosomal dominant mutation in one of

at least five keratin genes, KRT6A (encodes K6a pro-

tein), KRT6B (K6b), KRT6C (K6c), KRT16 (K16) and

KRT17 (K17).1–3 These mutations classify PC clinical

subtypes as PC-K6a, PC-K6b, PC-K6c, PC-K16 and PC-

K17, respectively.4 There are currently 619 genetically

confirmed cases of PC worldwide.5 PC prevalence in

western developed nations is 0.9 cases per million,6

and extrapolation suggests a worldwide PC population

of 6500, consistent with previous estimates.7

The clinical phenotype of PC is a triad of nail dys-

trophy, plantar keratoderma (Fig. 1) and plantar

pain.4,8 PC keratoderma is exquisitely painful, espe-

cially on weight-bearing areas. Other common clinical

manifestations include: cysts, follicular hyperkeratosis,

oral leucokeratosis and palmar keratoderma.

Correspondence: Dr Tim Wallis, University Hospitals Southampton,

Southampton General Hospital, Tremona Road, Southampton, Hampshire,

SO16 6YD, UK

E-mail: [email protected]

Conflict of interest: the authors declare that they have no conflicts of

interest.

Accepted for publication 11 March 2015

Clinical and Experimental Dermatology 1ª 2015 British Association of Dermatologists

Keratins are key structural proteins that impart

structural strength and integrity to epithelial cells and

tissues. Defective processing of the keratin cytoskeleton

can cause fragility in epithelial cells and tissues in

which the defective keratin is expressed.9 PC keratins

are predominantly expressed in keratinocytes of the

nail, palmoplantar skin and oral mucosa.

Physical pain is either nociceptive or neuropathic.

Nociceptive pain arises from actual or threatened tis-

sue damage, and involves the activation of nocicep-

tors, whereas neuropathic pain (NeP) arises from

damage or disease to the somatosensory nervous sys-

tem.10 Patients with NeP may experience abnormal

sensations such as burning, tingling or numbness, in

addition to persistent or paroxysmal pain independent

of painful stimuli. The treatment of NeP is often unre-

sponsive to typical agents used for nociceptive pain.11

Pain is an over-riding symptom of PC, but there has

been little research into its nature. In this study, we

investigated pain in PC, including its characteristics,

severity and effect on quality of life (QoL). Validated

patient-reported outcome questionnaires (PROs) and

clinical assessment measured the prevalence of neuro-

pathic pain and QoL within PC subtypes. A better

understanding of the nature of pain in PC and the

associated burden of illness should enable more appro-

priate management.

Methods

This observational study had full ethics approval from

the institutional review board [WIRB Study number

IPCRR (registry): 20040468, WIRB Study number for

the pain study: 20111060, Western IRB, Olympia,

WA, USA], and all recruited subjects provided

informed written consent.

Selection criteria and participants

Study subjects had to meet all of the following inclu-

sion criteria: (i) age 18–90 years inclusive, (ii) prior

diagnosis of PC with confirmed genotype and (iii) abil-

ity to understand and comply with the study as judged

by the investigator (BH). Patients were ineligible if

they met any of the following exclusion criteria: (i)

lack of consent capacity, (ii) secondary skin infections

of the feet, (iii) diabetes-related or other distal sensory

neuropathy, (iv) NeP conditions caused by any other

injury, (v) any unstable disease incompatible with the

study objectives or (vi) any psychiatric disorder con-

founding reliable information-gathering.

In total, 35 adult patients (17 men, 18 women;

mean � SD age 45.8 � 16.0, range 18–84 years)

with genetically confirmed PC registered in the Interna-

tional PC Research Registry (IPCRR)12 and attending a

patient support meeting focusing on pain in PC were

invited to participate in the study. The study comprised

three different components: (i) self-assessment question-

naires [the Brief Pain Inventory ((BPI),13 a neuropathic

pain symptom inventory (painDETECT)14 and a generic

QoL instrument (EQ-5D-3L)15]; (ii) standardized quanti-

tative sensory testing (QST);16 and (iii) clinical evalua-

tion by an experienced pain physician. The clinical

assessments were conducted within a fully air-

conditioned hotel, in Philadelphia (USA) during August

2010. Patients continued all their regular medications

including analgesics during the study period (Table 1).

Questionnaires

Brief Pain Inventory. The short-form BPI (BPI-SF)13 is

a validated questionnaire frequently used for measur-

ing pain, and is suitable for either patient self-report-

ing or interviewer administration.17 BPI-SF records

the severity of pain and its effect on daily function-

ing. Each BPI question is scored from 0 to 10, from

which two indices, pain severity (ranging from ‘no

pain’ to ‘worst imaginable pain’) and pain interfer-

ence with daily life (from ‘does not interfere’ to ‘com-

pletely interferes’), are derived.

(a) (b)

(c) (d)

Figure 1 (a–d) Callus state of plantar kertoderma in pachyony-

chia congenita evident in a selection of research subjects with

different keratin subtypes: (a) K16, (b) K17, (c) K6a and (d) K6b.

ª 2015 British Association of Dermatologists2 Clinical and Experimental Dermatology

Can skin disease cause neuropathic pain? � T. Wallis et al.

painDETECTTM. The painDETECT questionnaire is a

validated patient-reported outcome (PRO) instrument

with high sensitivity and specificity for predicting

NeP.14 Four sections assess the intensity, localization,

pattern and quality of pain. Summary scores ≤ 12

indicate that NeP is unlikely, scores of 13–18 suggest

pain of uncertain/mixed aetiology and scores ≥ 19

denote prominent NeP.18

EQ-5D. EQ-5D-3L assesses health-related (HR)QoL15

and consists of a five-item questionnaire (mobility, self-

care, usual activities, pain/discomfort and anxiety/

depression) and a visual analogue scale (VAS). Each

question has three levels of response (‘no problem’,

‘some problems’ or ‘severe problems’). Individual

patient responses to the EQ-5D index questionnaire

were converted to a single summary societal prefer-

ence measure of health utility using the US tariff.19

The EQ-5D VAS is a linear score, with 100 represent-

ing ‘best imaginable health state’ and 0 representing

‘worst imaginable health state’.

Quantitative sensory testing

QST is a noninvasive method for testing the integrity

of sensation in neurological disorders.16 We used a

four-stage paradigm to measure both loss of sensation

and hypersensitivity in the lower limbs. Time con-

straints limited these tests to those expected to have

the greatest sensitivity in this population, namely:

Table 1 Subject characteristics by PC subtype.*

Parameter

PC (keratin) subtype

Overall PK6a K6b K16 K17

n 11 3 14 7 35

Sex (M/F), % 55/46 67/33 64/36 14/86 51/49 0.16†Age, years 45 (8) 44 (23) 52 (19) 41 (17) 47 (16) 0.44‡BMI, kg/m2 25.6 � 6.2 23.5 � 2.4 27.2 � 4.9 27.8 � 5.2 26.5 � 5.2 0.60‡BPI severity 4.7 � 1.5 3.4 � 0.6 4 � 1.8 4.2 � 1.9 4.2 � 1.7 0.60‡BPI interference 5.3 � 2.4 3.1 � 1.8 3.5 � 1.7 5.1 � 2.5 4.4 � 2.2 0.13‡EQ-5D index 0.61 � 0.20 0.87 � 0.12 0.76 � 0.11 0.58 � 0.21 0.70 � 0.18 0.02‡EQ-5D VAS 75.4 � 15.3 94 � 3.6 79.4 � 11.8 64.8 � 25.3 77 � 17 0.08‡painDETECT score 19.1 � 6.5 10.7 � 10.3 12.2 � 6.4 17.3 � 7.3 15 � 7 0.07‡painDETECT class, %

Nociceptive 27 67 50 14 37 0.02†Mixed 9 0 36 71 31

Neuropathic 64 33 14 14 31

Clinical examination, %

Nociceptive 9 67 57 43 40 0.33†Mixed 18 0 21 14 17

Neuropathic 73 33 21 43 43

QST, %

MDT abnormal 9 0 14 57 20 0.05†MPT abnormal 55 0 64 57 54 0.25†WUR abnormal 27 33 29 29 29 0.10†VDT abnormal 9 0 7 29 11 0.44†

QST abnormality, %

None 18 67 14 14 20 0.18†1 55 33 36 14 37

2+ 27 0 50 71 43

Painkiller used, %

Opiate 0 0 7 43 11 0.03†Anticonvulsant 0 0 0 14 3 0.25†Antidepressant 18 0 7 14 11 0.76†NSAID 55 0 71 71 57 0.12†Aspirin/paracetamol 18 0 7 0 8 0.52†Topical analgesia 18 0 7 0 8 0.52†Other analgesia 9 0 7 0 5 0.82†

BPI, Brief Pain Inventory; MDT, mechanical detection threshold; MPT; mechanical pain threshold; NSAID, nonsteroidal anti-inflammatory

drug; PC, pachyonychia congenita; QST, quantitative sensory testing; VAS, visual analogue score; VDT, vibration detection threshold;

WUR; wind-up pain ratio. *Data are mean � SD unless otherwise specified; †v² test for proportions; ‡ANOVA.



(i) mechanical (touch) detection threshold (MDT); (ii)

pressure-evoked pain (mechanical pain threshold;

MPT; (iii) repeated tapping of the skin using a non-

painful filament (wind-up pain ratio; WUR); and (iv)

vibration detection threshold (VDT). Thermal testing

of patients with PC was considered inappropriate

because of the dense plantar hyperkeratosis. Operators

were fully competent in the application of QST, and

patients received practice and training prior to data

collection.

The QST protocol was similar to that developed by

Rolke et al.,16 except that only the feet (the primary

site for PC pain) were assessed, in line with recom-

mended practice for bilateral NeP conditions. QST

scores were converted to z-scores using published

population mean reference values specific to sex, age

group and anatomical site.16

Clinical examination

A clinical examination taking 30 min was carried out

by an experienced consultant specializing in the man-

agement of chronic pain (BH).

Statistical analysis

Statistical comparisons between PC subtypes were

made by ANOVA for continuous variables and the v²test for categorical variables. Correlations between

continuous variables were made with curve estimation

(a)

(c) (d)

(b)

Figure 2 Individual patient quantitative sensory testing (QST) parameter scores by pachyonychia congenita (PC) subtype. (a) Mechani-

cal detection threshold (MDT) (green, K6a; purple, K6b; blue, K16; orange K17). (b) Mechanical pain threshold (MPT) (solid, right foot;

clear, left foot). (c) wind-up ratio (WUR). Z-scores represent individual score standardized for population reference values specific to sex,

age and anatomical site. Scores within � 1.96 SD of the age-/sex-/site-specific population mean are considered to be ‘normal’ (grey

shading), while scores > 1.96 SD represent hypersensitivity to evoked stimuli and scores < 1.96 SD represent loss of function. (d) Vibra-

tion detection threshold (VDT).



regression. All analyses were conducted using IBM

SPSS Statistics (v20; IBM Inc., Armonk, NY,USA).

Results

Subjects

Subject numbers in each gene classification were: K6A

n = 11, K6B n = 3, K16 n = 14 and K17 n = 7, and

mean body mass index (BMI) was 26.5 � 5.2 kg/m2.

Comorbidity was generally low in this cohort of rela-

tively young active adults. There were no statistically

significant demographic differences between PC sub-

types (Table 1).

Pain characteristics

BPI pain severity and pain interference were similar

across subtypes, with overall means of 4.2 � 1.7 and

4.4 � 2.2, respectively.

A trend for higher painDETECT scores was observed

in the K6a and K17 subtypes (mean scores of

19.1 � 6.5 and 17.3 � 7.3 respectively) compared

with K6b or K16 subtypes (mean scores of 10.7 �10.3 and 12.2 � 6.4, respectively; P = 0.07). This

was reflected in a higher proportion of NeP cases in

the K6a group (64%) (P = 0.02). QoL appeared to be

lowest in the K17 group, with mean EQ-5D index and

VAS scores of 0.58 � 0.21 (P = 0.05) and 64.8 �25.3 (P < 0.08), respectively.

Figure 3 Relationship between painDETECT score and quality of

life (QoL) as represented by EQ-5D index (US tariff). painDETECT:

final score ≤ 12 indicates that neuropathic pain is unlikely,

scores of 13–18 indicate pain of uncertain/mixed aetiology and

and scores ≥ 19 indicate a significant neuropathic component to

the patient’s pain. EQ-5D index: US-specific societal preference for

health states. A score of 1 indicates ‘perfect health’, i.e. no

impairments; a score of 0 indicates a state of health equivalent

to death i.e. the ‘average’ US citizen would trade all their

remaining lifespan to avoid such health states. Best fit trend line

represent cubic function (R2 = 0.26, P = 0.02),

(a) (b)

Figure 4 Association of EQ-5D index (US tariff) with Brief Pain Inventory (BPI) indices: (a) BPI Severity (quadratic function R2 = 0.19,

P = 0.121) and (b) BPI Interference (linear function R2 = 0.12, P < 0.05).



QST indicated that most patients with PC experi-

enced abnormal detection of pressure-invoked pain;

55% of K6a, 64% of K16, and 57% of K17 patients

showed altered MPT function, whereas this was not

the case for the K6b subtype. In addition, 57% of K17

patients exhibited abnormal detection threshold for

touch (assessed by MDT) (P < 0.05). Variation in QST

parameters is illustrated in Fig. 2.

The predominant (by 57%) type of pain relief used

by these patients was nonsteroidal anti-inflammatory

drugs (NSAIDs), although opiates were used by

nearly half of K17 patients (43%) (P = 0.03). Few

patients took medications considered helpful for

neuropathic pain (antidepressant 11%, anticonvul-

sant 3%).

Correlations

There was a significant cubic correlation (P = 0.02)

between painDETECT score and EQ-5D index (Fig. 3),

but not BPI severity (P = 0.121). A weak negative

linear relationship between EQ-5D index and BPI pain

interference (Fig. 4) was also observed. QST abnormal-

ity was not discriminated by painDETECT score

(a) (b)

(c) (d)

Figure 5 Association between quantitative sensory testing (QST) item abnormality and painDETECT score. (a) mechanical detection

threshold (t-test P = 0.54); (b) mechanical pain threshold (t-test P = 0.23); (c) wind-up ratio (t-test P = 0.98); (d) vibration detection

threshold (t-test P = 0.85). For each parameter, ‘1.00’ denotes presence of an abnormal score, i.e. patient has at least one z-score either

> 1.96 SD or > �1.96 SD the age-/sex-/site-standardized population mean. ‘0.00’ denotes no abnormal score recorded.



(Fig. 5), although a nonsignificant trend (P < 0.08)

was seen for variation in painDETECT scores across

clinical investigator assignment of nociceptive pain,

mixed pain and NeP (Fig. 6).

Discussion

The nature of pain in PC (NeP or nociceptive pain)

and a quantitative assessment of its effect on QoL

has not been reported previously. As NeP is poorly

recognized,20 understanding the varied aetiology of

pain in PC will improve research to guide pain

management. All groups in this study reported mod-

erate to severe pain as assessed by the BPI. Pain

interfered with daily life in all PC subgroups of PC

and there was weak evidence to suggest that the

K17 and K6a groups may have been more severely

affected, although this difference was not statistically

significant (P = 0.13).

One-third of patients had predominately NeP while

another third had a mixture of NeP and nociceptive

pain, suggesting a five-fold greater prevalence of NeP in

patient with PC than in the general population.21,22

Despite this, only a minority of patients with PC were

receiving medications considered to be helpful in allevi-

ating NeP.

The mean EQ-5D index observed in this study

(0.67) is equivalent to that of patients with cardiac ill-

ness.23 Our analysis showed the poorest QoL in the

K17 and K6a patients, which were the groups with

the highest prevalence of NeP.

Patients with PC often experience severe pain on

walking. The majority of patients in our study had

increased sensitivity in the feet on QST testing, sug-

gesting that some of this discomfort is neuropathic in

origin. This was particularly evident in the K6a and

K17 patients.

Time constraints and limited patient availability

necessitated a reduced profile of QST testing. This

might be a potential weakness of our study; neverthe-

less, others have shown that NeP can be detected prior

to and following knee surgery using a similarly

reduced profile of QST tests.24,25

The triad for diagnosing NeP includes clinical exam-

ination. In this study, the diagnosis of NeP by clinical

examination correlated with the painDETECT question-

naire, indicating that this instrument might prove use-

ful for clinicians less experienced in diagnosing NeP in

this and other skin diseases.11

Conclusion

We have shown that NeP is an appreciable problem in

patients with PC. Recognizing NeP is important, as it

is known to be associated with significant impairment

of QoL and requires appropriate medication.26 The

painDETECT questionnaire combined with clinical

assessment will aid diagnosis of NeP in skin disease

and improve patient care.

Acknowledgements

We thank the QST operators J. Clapham and R. Dug-

gan for their assistance in undertaking this study, and

R. Knaggs for his help with reviewing the article. We

are grateful to the Pachyonychia Congenita Project for

funding, and to M. Schwartz (Director) for help with

the project. We are indebted to all the patients with

PC who participated in the study; it was a privilege to

work with them.

What’s already known about this topic?

● PC is a rare skin disorder caused by an autoso-

mal dominant mutation in keratin-encoding

genes.

● Pain is a significant symptom, and negatively

affects QoL.

Figure 6 painDETECT scores (PD_FINALSCORE) by clinical

assessment classification (ANOVA P < 0.08). Diagnostic clinical

classification (DX_CLINICAL_C): ‘No’, no clinical evidence of neu-

ropathic pain; ‘Mixed’, mixed nociceptive and neuropathic pain;

‘Yes’, predominantly neuropathic pain.



What does this study add?

● Pain is a primary symptom of PC, and a signifi-

cant proportion of this paitn is neuropathic in

nature.

● The effect of PC on QoL in adults has been

quantified.

● Understanding the aetiology of pain in PC will

enable more appropriate treatment.

References

1 Bowden PE, Haley JL, Kansky A et al. Mutation of a type

II keratin gene (K6a) in pachyonychia congenita. Nat

Genet 1995; 10: 363–5.2 McLean WH, Rugg EL, Lunny DP et al. Keratin 16 and

keratin 17 mutations cause pachyonychia congenita. Nat

Genet 1995; 9: 273–8.3 Smith F. A mutation in human keratin K6b produces a

phenocopy of the K17 disorder pachyonychia congenita

type 2. Hum Mol Genet 1998; 7: 1143–8.4 McLean WHI, Hansen CD, Eliason MJ, Smith FJD. The

phenotypic and molecular genetic features of

pachyonychia congenita. J Invest Dermatol 2011; 131:

1015–17.5 International PC Research Registry. Worldwide locations

of PC PATIENts in the IPCRR, 2015. Available at: http://

www.pachyonychia.org/upload/GRAPHS/

IPCRRLocationPCers_1.pdf (accessed 7 March, 2015).

6 Wikipedia. List of countries and dependencies by

population. Available at: http://en.wikipedia.org/wiki/

List_of_countries_and_dependencies_by_population

(accessed 7 March, 2015).

7 Kaspar RL. Challenges in developing therapies for rare

diseases including pachyonychia congenita. J Investig

Dermatol Symp Proc 2005; 10: 62–6.8 Eliason MJ, Leachman SA, Feng B, Schwartz ME, Hansen

CD. A review of the clinical phenotype of 254 patients

with genetically confirmed pachyonychia congenita. J Am

Acad Dermatol 2012; 67: 680–6.9 McLean WHI, Smith FJD, Cassidy AJ. Insights into

genotype–phenotype correlation in pachyonychia

congenita from the human intermediate filament

mutation database. J Investig Dermatol Symp Proc 2005;

10: 31–6.10 Treede R-D, Jensen TS, Campbell JN et al. Neuropathic

pain: redefinition and a grading system for clinical and

research purposes. Neurology 2008; 70: 1630–5.

11 Haanp€a€a M, Attal N, Backonja M et al. NeuPSIG

guidelines on neuropathic pain assessment. Pain 2011;

152: 14–27.12 The Pachyonchia Congenita Project. Available at: http:

//www.pachyonychia.org/.

13 Cleeland C. Pain assessment in cancer. In: Effect of Cancer

on Quality of Life (Osoba D ed). Boca Raston, FL: CRC

Press Inc., 1991; 293–305.14 Freynhagen R, Baron R, Gockel U, T€olle TR.

painDETECT: a new screening questionnaire to identify

neuropathic components in patients with back pain. Curr

Med Res Opin 2006; 22: 1911–20.15 The EuroQoL Group. EuroQol–a new facility for the

measurement of health-related quality of life. Health

Policy 1990; 16: 199–208.16 Rolke R, Baron R, Maier C et al. Quantitative sensory

testing in the German Research Network on Neuropathic

Pain (DFNS): standardized protocol and reference values.

Pain 2006; 123: 231–43.17 Keller S, Bann CM, Dodd SL et al. Validity of the Brief Pain

Inventory for use in documenting the outcomes of patients

with noncancer pain. Clin J Pain 2004; 20: 309–18.18 Bennett MI, Attal N, Backonja MM et al. Using screening

tools to identify neuropathic pain. Pain 2007; 127: 199–203.

19 Shaw JW, Johnson JA, Coons SJ. US valuation of the EQ-

5D health states: development and testing of the D1

valuation model. Med Care 2005; 43: 203–20.20 Baron R, Binder A, Wasner G. Neuropathic pain:

diagnosis, pathophysiological mechanisms, and

treatment. Lancet Neurol 2010; 9: 807–19.21 Torrance N, Smith BH, Bennett MI, Lee AJ. The

epidemiology of chronic pain of predominantly

neuropathic origin. Results from a general population

survey. J Pain 2006; 7: 281–9.22 Bouhassira D, Lant�eri-Minet M, Attal N et al. Prevalence

of chronic pain with neuropathic characteristics in the

general population. Pain 2008; 136: 380–7.23 Sullivan PW, Ghushchyan V. Preference-based EQ-5D

index scores for chronic conditions in the United States.

Med Decis Making 2009; 26: 410–20.24 Martinez V, Fletcher D, Bouhassira D et al. The evolution

of primary hyperalgesia in orthopedic surgery:

quantitative sensory testing and clinical evaluation

before and after total knee arthroplasty. Anesth Analg

2007; 105: 815–21.25 Wylde V, Palmer S, Learmonth ID, Dieppe P. The

association between pre-operative pain sensitisation and

chronic pain after knee replacement: an exploratory

study. Osteoarthritis Cartilage 2013; 21: 1253–6.26 Freynhagen R, Bennett MI. Diagnosis and management

of neuropathic pain. Br Med J 2009; 339: 391–5.



http://www.pachyonychia.org/upload/GRAPHS/IPCRRLocationPCers_1.pdf



http://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_population

http://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_population

http://www.pachyonychia.org/

A Large Mutational Study in Pachyonychia CongenitaNeil J. Wilson1, Sancy A. Leachman2, C. David Hansen2, Alexandra C. McMullan1, Leonard M. Milstone3,Mary E. Schwartz4, W.H. Irwin McLean1, Peter R. Hull5 and Frances J.D. Smith1

Pachyonychia congenita (PC) is a rare autosomal dominant skin disorder characterized predominantly by naildystrophy and painful palmoplantar keratoderma. Additional clinical features include oral leukokeratosis,follicular keratosis, and cysts (steatocysts and pilosebaceous cysts). PC is due to heterozygous mutations in oneof four keratin genes, namely, KRT6A, KRT6B, KRT16, or KRT17. Here, we report genetic analysis of 90 newfamilies with PC in which we identified mutations in KRT6A, KRT6B, KRT16, or KRT17, thereby confirming theirclinical diagnosis. A total of 21 previously unreported and 22 known mutations were found. Approximately halfof the kindreds had mutations in KRT6A (52%), 28% had mutations in KRT16, 17% in KRT17, and 3% of familieshad mutations in KRT6B. Most of the mutations were heterozygous missense or small in-frame insertion/deletion mutations occurring within one of the helix boundary motif regions of the keratin polypeptide. Moreunusual mutations included heterozygous splice site mutations, nonsense mutations, and a 1-bp insertionmutation, leading to a frameshift and premature termination codon. This study, together with previouslyreported mutations, identifies mutation hotspot codons that may be useful in the development of personalizedmedicine for PC.

Journal of Investigative Dermatology advance online publication, 17 February 2011; doi:10.1038/jid.2011.20

INTRODUCTIONPachyonychia congenita (PC) is a rare genetic skin disorderthat is associated with mutations in one of four keratin genes,KRT6A, KRT6B, KRT16 or KRT17 (Bowden et al., 1995;McLean et al., 1995; Smith et al., 1998). The most strikingfeature of PC is the painful and debilitating plantarkeratoderma (Figure 1). The mechanism underlying theplantar pain is poorly understood; however, the formationof blisters beneath the keratoderma is likely to be a majorcontributing factor. Palmar keratoderma is less frequent. Naildystrophy presents in variable forms, from very minor oralmost absent nail changes through to the classic hyper-trophic nail dystrophy that gives the condition its name(Leachman et al., 2005; Figure 1). Other epithelial structurescan be affected, particularly the mucosae and the piloseba-cesous unit. A more detailed description of the disorder isgiven in McLean et al. (2011).

Historically, PC has been subdivided into two subtypes,PC-1 (Jadassohn–Lewandowski type) or PC-2 (Jackson–Lawlertype), on the basis of the clinical presentation alone

(Jadassohn and Lewandowski, 1906; Jackson and Lawler,1951). A combination of factors have led to the suggestionthat PC should be reclassified. First, the advent of moleculargenetics and the identification of the genes causing PCprovide a rational means of classifying patients. Second,clinical analysis of the large case series collected by theInternational Pachyonychia Congenita Research Registry(IPCRR), fully linked to molecular genetic data, has shownthat there is considerable phenotypic overlap between thehistorical PC-1 and PC-2 subtypes (Eliason et al., 2011). Thus,a new molecular genetic classification has been adopted,fully supported by members of the International Pachyony-chia Congenita Consortium, whereby the subtypes of PC referto the mutated keratin gene (PC-6a for a patient carrying aK6a mutation, PC-6b, PC-16, PC-17, and so on). Thedesignation ‘PC-U’ is used for cases where the causativegene is unknown (McLean et al., 2011). The new classifica-tion will (a) help discourage publication of spurious casereports lacking molecular data (often with misdiagnosedcases or cases with coincidental findings unrelated to PC)and (b) allow better prognostic predictions and patientcounseling, especially when referenced to the IPCRR clinicaldata set.

The 54 human keratins belong to the intermediate filamentprotein family that consists of at least six types; keratins makeup the type I and type II intermediate filament proteins. Amajor function of keratins is to form structural cytoskeletalnetworks within epithelial cells that allow cells to withstandeveryday stress and physical trauma. Keratins are expressedin pairs in tissue-specific and differentiation-specificpatterns (Lane, 1993). The keratins associated with PC,K6a, and K16, K6b and K17 are predominantly expressed

& 2011 The Society for Investigative Dermatology www.jidonline.org 1

ORIGINAL ARTICLE

Received 26 August 2010; revised 29 December 2010; accepted 5 January2011

1Division of Molecular Medicine, University of Dundee, Dundee, UK;2Department of Dermatology, University of Utah, Salt Lake City, Utah, USA;3Department of Dermatology, Yale University, New Haven, Connecticut,USA; 4PC Project, Salt Lake City, Utah, USA and 5Department ofDermatology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Correspondence: Frances J.D. Smith, Division of Molecular Medicine,Medical Sciences Institute, University of Dundee, Dundee DD1 5EH, UK.E-mail: [email protected]

Abbreviations: IPCRR, International Pachyonychia Congenita ResearchRegistry; K, keratin protein; KRT, keratin gene; PC, pachyonychia congenita

http://dx.doi.org/10.1038/jid.2011.20



in basal/suprabasal layers of palmoplantar skin, as well as inepidermal appendages and oral mucosa. In PC, theseepithelial cell compartments are rendered fragile by theexpression of dominant-negative mutant keratins. All cases ofPC with a confirmed molecular diagnosis, including those inthe literature, http://www.interfil.org (Szeverenyi et al.,2008), and those in this study, are due to heterozygousdominant-negative mutations, inherited as an autosomaldominant trait. Although there are a small number of casereports of PC with recessive inheritance in the literature, thereare no reports of recessive PC with a confirmed moleculardiagnosis.

All keratins share a common protein structure consisting ofa central a-helical rod domain of 310 amino acids subdividedinto the 1A, 1B, 2A, and 2B domains. These domains areconnected by non-helical linker regions, L1, L12, and L2. Therod domain is flanked by short regions of sequence homology(H1 and H2 regions), followed by the variable, non-helicalhead (V1) and tail domains (V2). At either end of the roddomain are the helix boundary motifs (the helix initiationmotif and the helix termination motif). These highlyconserved motifs are thought to be important in mediatingend-to-end interactions during filament assembly. Themajority of mutations in PC occur in these helix boundarymotifs, emphasizing the critical importance of these se-quences for correct keratin filament formation and themechanical resilience of epithelial cells.

The IPCRR was established in 2004 by the patientadvocacy group, Pachyonychia Congenita Project (http://www.pachyonychia.org). At the time of writing, 478 familiesare registered (928 individuals), 223 families have completedthe detailed questionnaire (Eliason et al., 2011) and 199families have undergone genetic testing. Genetic testingresults from some of these cases have been previouslypublished (McLean et al., 1995; Smith et al., 1997, 2000,2005; Liao et al., 2007a; Oh Adib et al., 2008; Cogulu et al.,2009; Gruber et al., 2009).

Here, we present the findings of 90 new families withmutations in KRT6A, KRT6B, KRT16, or KRT17. Within thiscase series, we identified 21 previously unreported mutations(22 families) and 22 known mutations (68 families). Thismutation analysis study not only confirms the clinicaldiagnosis of these individuals but, together with previouslyreported mutations (http://www.interfil.org), also identifiesmutation hotspot codons that may be useful in the develop-ment of future allele-specific therapies.

RESULTSClinical details

All individuals involved in this study were recruited throughthe IPCRR, an ongoing research program to identify PCpatients worldwide. This research registry is approved by aninstitutional review board that complies with all principles ofthe Helsinki Accord (Western IRB Study no. 20040468). An

K6a p.Asn171Lys (siblings)

K6a p.Asn171Ser

K6a p.Asn172del

K16 p.Asn125Ser K16 p.Arg127Pro K16 p.Arg127Pro K17 p.Asn92_Leu99del

K6a p.Leu468Pro

K6a p.Asn171Lys (siblings)

Figure 1. Clinical features of pachyonychia congenita (PC). Plantar keratoderma and nail dystrophy in PC patients with known keratin mutations. Mutations are

annotated. Note the variation in severity and clinical appearance of these features.


NJ Wilson et al.Pachyonychia Congenita

http://www.interfil.org




important part of this study was the detailed clinicalconsultations that were performed for all cases analyzed.This bank of data allows us now, and in the future as thenumber of cases analyzed increases, to identify any usefulgenotype–phenotype correlation for PC. The predominantclinical features of individuals involved in this study aresummarized in Supplementary Table S1 online. Of the 90families analyzed, 36 represent familial occurrence of PC,with many showing autosomal dominant inheritancethrough several generations; the remaining 54 cases representspontaneous mutations.

Both common and rare dominant mutations cause PCWithin this large PC case series, pathogenic mutations wereidentified in the KRT6A gene in approximately half (52%) ofthe kindreds, whereas 28% had mutations in KRT16, 17%had defects in KRT17, and 3% had mutations in KRT6B (seeFigure 2 and Supplementary Table S1 online). Mutations inKRT6A also account for B50% of previously reported casesof PC (http://www.interfil.org), consistent with our findinghere that this is the predominant PC gene. The majority of themutations we identified in all four genes were heterozygousmissense mutations occurring within one of the helixboundary motif regions. In addition, we found somesmall in-frame insertion/deletion mutations and, in particular,the common K6a p.N172del mutation was identified in16 families.

An unusual V2 domain mutation in one PC family

A more unusual mutation identified was a 1-bp insertionin exon 9 of KRT6A, the last exon of this gene (K6ac.1511_1512insG). This insertion results in a frameshift anda premature stop codon just two amino acids upstream of thenatural stop codon, whereby the last 60 amino acids of theK6a V2 domain are exchanged for a foreign peptide of 58amino acids. Protein–protein BLAST (basic local alignmentsearch tool) analysis showed that this mutant peptidesequence has no significant similarity to any human protein(data not shown; http://blast.ncbi.nlm.nih.gov/). Kyte–Doolit-tle hydrophilicity analysis revealed that the normal K6a V2domain consists of alternating hydrophobic and hydrophilicsequences, followed by a short hydrophilic C terminus(Figure 3), consistent with the glycine-loop structureproposed by Steinert for keratin variable domains (Korgeet al., 1992). In contrast, the mutant V2 domain is almostcompletely hydrophilic (Figure 3). In terms of protein

KRT6B3%

KRT1717%

KRT6A52%

KRT1628%

KRT6A

KRT16

KRT17

KRT6B

Figure 2. Mutational spectrum in pachyonychia congenita (PC). Pie chart

showing percentage of families in this study with mutations in the four keratin

genes, namely, KRT6A, KRT6B, KRT16, and KRT17.

a Normal K6a V2 domain

Kyte–Doolittle hydrophilicity: Window = 7

Hyd

roph

ilici

ty

4.03.02.01.00.0

–1.0–2.0

10

Rob

son–

Gar

nier

400

200

0

–200

–400

–60010 20 30 40 50

Robson–Garnier 2° structure: Window = 7

Helix Sheet Turn

20 30 40 50

b Frameshift mutant K6a V2 domain

Kyte–Doolittle hydrophilicity: Window = 74.03.02.01.00.0

–1.0–2.0–3.0–4.0

10 20 30 40 50

600

400

200

0

–200

–400

Robson–Garnier 2° structure: Window = 7

Helix Sheet Turn

10 20 30 40 50

Figure 3. Kyte–Doolittle hydrophilicity analysis of normal and mutant K6a V2 domain. (a) The normal K6a V2 domain consists of alternating hydrophobic and

hydrophilic sequences, followed by a short hydrophilic C terminus, whereas (b) the mutant V2 domain is almost completely hydrophilic.

www.jidonline.org 3



http://blast.ncbi.nlm.nih.gov/


secondary structure predicted by Robson–Garnier analysis,the normal K6a V2 domain is predicted to adopt three largeareas of sheet conformations, separated by short regionspredicted to adopt turn conformations (Figure 3). Thiscontrasts with the mutant V2 domain, which is predicted toconsist largely of turn conformation with one helical regionnear the C terminus (Figure 3). This in silico analysisunderscores the fact that the mutant polypeptide is verydifferent in both sequence and predicted secondary structurefrom the wild-type K6a tail domain, consistent with adominant-negative gain-of-function mutation, as seen inother keratinizing disorders due to C-terminal frameshiftmutations in K1 (Sprecher et al., 2001, 2003; Richardson et al.,2006) or K5 (Sprecher et al., 2003). In the case of loricrinkeratoderma, a similar C-terminal gain-of-function mutation hasbeen shown to lead to creation of a new nuclear localizationsignal, which in turn leads to nuclear accumulation of mutantprotein (Ishida-Yamamoto et al., 2000). The mutant K6apolypeptide sequence generated here was analyzed forpotential nuclear localization signal motifs (http://cubic.bioc.columbia.edu/services/predictNLS/), but none were found.

Splice site mutations identified in five kindredsInterestingly we also detected four previously unreportedsplice site mutations (in five families) at the intron 1/exon 2boundary of KRT6A. These are clearly inherited in anautosomal dominant manner. Unfortunately, we were unableto obtain mRNA from lesional skin that would allow analysisof the effects of these genomic mutations on RNA splicing.One possible predicted consequence of this type of mutationis skipping of exon 2; however, as this is an out-of-frameexon, its deletion would lead to a frameshift and prematuretermination codon. This is unlikely to create a dominant-negative mutant protein, because nonsense-mediated mRNAdecay is predicted to occur, leading to loss of expression ofthis allele. In the case of KRT5 and KRT1, both of which aretype II keratin genes closely related to KRT6A, analogousmutations have been reported affecting the intron 1 splicesites (Rugg et al., 1999; Terron-Kwiatkowski et al., 2002). Inboth these genes, the mutation led to activation of anidentical cryptic splice site in exon 1, producing a 66-nucleotide (22 amino acid) in-frame deletion. Given thestrong sequence homology between these genes, it isprobable that a similar mechanism will also occur with theseKRT6A splice site mutations.

Nonsense mutations in a few PC familiesIn addition, two heterozygous nonsense mutations were alsoidentified in PC cases. One of these was identified in the 2Bdomain of K6a, p.Gln435X, which is predicted to lead toexpression of a truncated dominant-negative K6a protein,lacking the end of the rod domain and the tail domain.Because this mutation is close to the natural stop codon ofK6a, it is likely to escape nonsense-mediated decay to someextent and, therefore, be expressed as mutant polypeptide(Frischmeyer and Dietz, 1999). Analogous mutations havebeen seen in K5 in dominantly inherited epidermolysisbullosa simplex (Muller et al., 1999; Livingston et al.,2001). The other nonsense mutation was found within thehead domain of K16, p.Lys15X. Analogous prematuretermination codon mutations just downstream of the ATGcodon have been reported in other dominant keratindisorders, including K5 in Dowling–Degos disease (Betzet al., 2006; Liao et al., 2007b) and in K14 in Naegelisyndrome (Lugassy et al., 2006). Although it remains some-what unclear whether these mutations act via haploinsuffi-ciency or via expression of a dominant-negative mutantprotein through use of an alternative initiation codon(McLean et al., 2003), it is however clear that they exhibitdominant inheritance (Betz et al., 2006; Lugassy et al., 2006).Unfortunately, in the case of the two nonsense mutationsidentified here, it was not possible to obtain tissue to allowanalysis of mRNA or protein.

A spectrum of keratin mutations cause PC

For each of the four genes associated with PC, it has beensuggested that there are some codons that represent mutationhotspots, as well as several rare or even family-specific muta-tions. Our results confirm the previously identified mutationhotspots and also identify 21 previously unreported mutations.Table 1 summarizes the data from previous publications(http://www.interfil.org) together with the data from this largecase series.

DISCUSSIONThe mutation results from this PC case series of 90 families,together with those from at least 131 previously reportedcases (http://www.interfil.org), provides a large data set foranalysis in terms of where mutations occur within the keratinprotein, the most common mutations, the types of mutationsfound, and allows for preliminary genotype–phenotype

Table 1. Summary of mutations identified in this study and previous publications

GeneNumber of

different mutationsNumber of

recurrent mutations Most common mutation site

KRT6A 39 13 K6a p.Asn171—as missense or deletion mutation (K6a p.Asn172del), this codon is mutated in 46%

of those with KRT6A mutations, of which p.Asn172del accounts for 30% of all KRT6A mutations

KRT16 19 8 K16 p.Leu132Pro in 23% of families with KRT16 mutations

KRT17 22 8 K17 p.Asn92Ser in 36% of families with KRT17 mutations

KRT6B 4 1 K6b p.Glu472Lys in 71% of families with KRT6B mutations



http://cubic.bioc.columbia.edu/services/predictNLS/

http://cubic.bioc.columbia.edu/services/predictNLS/



correlation. All cases with confirmed PC have a mutation inone of the four keratin genes associated with this disease,KRT6A, KRT6B, KRT16, and KRT17. In the course of runningthe international mutation screening service for PC, inconcert with the IPCRR, we have received a small numberof samples from isolated cases or families in which nomutation was found in these four keratin genes. In thesecases, careful review of the clinical phenotype by theInternational Pachyonychia Congenita Consortium cliniciansoften has often led to correction of the diagnosis, confirmedby analysis of other keratin genes or non-keratin genes. Forexample, a few cases, in which there is alopecia in additionto nail dystrophy, have turned out to carry heterozygousconnexin-30 mutations (Lamartine et al., 2000; Smith et al.,2002; van Steensel et al., 2003). Thus, Clouston syndromeshould be considered in the differential diagnosis for PC.Similarly, a few families presenting with painful but verylimited, circumscribed focal plantar keratoderma, withminimal or absent nail changes, have recently been shownto have mutations in the gene encoding K6c (KRT6C; Wilsonet al., 2010). Taking these families into account, we have asmall number of families (o5%) in which careful clinicalevaluation is consistent with a diagnosis of PC and in whomwe cannot detect a mutation in any exon or splice sites of thefour PC keratin genes. Genetic linkage analysis in at least onesuch family has yielded statistically significant linkage to thevicinity of a keratin gene cluster (FJD Smith, unpublisheddata), and so we conclude that there are either intronic orgenomic deletion/rearrangement mutations that are missedby conventional PCR analysis, or that at least one otherkeratin gene or a nearby related gene can lead to a PC-likephenotype in a minority of cases. Sequence analysis of thesecases is ongoing in the laboratory.

All PC causative mutations found to date are heterozygouschanges that exhibit autosomal dominant inheritance with aproven, or very probable, dominant-negative pathomechan-ism. It is important to note that no recessive cases of PC havebeen confirmed at the molecular level, despite a few casereports appearing in the literature, in which, for example,recessive inheritance may have been suggested by coin-cidental consanguinity. It is therefore important that casereports of already characterized genetic diseases be backedup by molecular analysis, otherwise the literature maybecome misleading. The recurrence risk of a sporadic caseof a dominant disorder is very low (involving only the risk ofgonadal mosaicism) which is difficult to estimate withcertainty. In the dominant disorder achondroplasia OMIMno. 100800, this is of the order of one in a few hundred(Mettler and Fraser, 2000); however, in epidermolysis bullosasimplex, this has been estimated at 2–5% (Pfendner et al.,2005). In contrast, the recurrence risk for a recessive conditionis as high as 25%. Thus, there are important genetic counselingimplications in the correct assignation of inheritance patterns.So far, we have confirmed gonadal mosaicism in only one PCfamily out of 199 analyzed from the IPCRR.

The majority of the mutations causing PC are located inone of the helix boundary motifs of the mutated protein, andmost of the causative variants are missense or small in-frame

insertion–deletion mutations. Less common types identifiedinclude splice site and premature termination codon muta-tions. There are a number of mutation ‘hotspot’ codons foreach of the keratin genes associated with PC as well asmutations that appear to be family specific (Table 1). Themost commonly mutated codon is K6a p.Asn171, either as amissense mutation (e.g. p.Asn171Lys and p.Asn171Ser) or asa deletion mutation (designated as p.Asn172del using theHuman Genome Variation Society guidelines; http://www.hgvs.org). Approximately half of the families with identifiedKRT6A mutations have a mutation at this site; the mostcommon PC mutation is the p.Asn172del mutation that, todate, has been found in 32 out of 221 PC families (14%) withknown mutations (http://www.interfil.org and this study).

Despite the increased number of genotyped individualsand families, there is no apparent correlation between theclinical features observed and the protein domain harboringthe mutation in PC. Nevertheless, there are two mutations inKRT16 in which the actual amino acid substitution appears tocorrelate with the severity of the clinical phenotype (see Fuet al., 2011). There are also some differences in clinicalfeatures depending on the gene involved, such as thepresence of natal teeth in many, but not all, individuals withKRT17 mutations (Eliason et al., 2011). In PC, there can alsobe variation in clinical severity between mutations in thesame gene and even between individuals with the samemutation. Polymorphisms, copy number variation, environ-mental factors, lifestyle, and patient care may account forsome of this clinical variation. Therefore, an importantconclusion of this large study of a keratin disorder is thatPC can really be considered as a spectrum of phenotypesranging from very mild to more severe, in which (a) theparticular gene involved appears to have a moderateinfluence on phenotype and (b) the specific mutationgenerally appears to have little influence on phenotype.

The detailed clinical information that is obtained by theIPCRR also identified several cases, which were not includedin this study, that presented with both typical and atypicalfeatures of PC and that were unlikely due to a mutation in anyof the four keratin genes, KRT6A, KRT6B, KRT16, or KRT17.These were analyzed for mutations in other candidate genes.For example, several families presented with varying degreesof alopecia in addition to some features typical of PC, whichwas suggestive of Clouston syndrome (Lamartine et al., 2000;Smith et al., 2002; van Steensel et al., 2003) and mutationswere subsequently identified in GJB6 (which encodes con-nexin 30). Another candidate gene considered for individualspresenting with palmoplantar keratoderma was the third K6gene (KRT6C). We have identified mutations in KRT6C inseveral families presenting with palmoplantar keratoderma,but with only mild/no nail changes (Wilson et al., 2010).

Genetic analysis of individuals with PC not only confirmstheir clinical diagnosis but also aids in genetic counseling.The identification of mutations is especially important for thedesign of future mutation-specific and/or gene-specifictherapies and, hence, the large, well-phenotyped, and fullygenotyped case series we report here is an invaluableresource for future clinical trials.

www.jidonline.org 5


http://www.hgvs.org

http://www.hgvs.org



MATERIALS AND METHODSClinical material

Genomic DNA was obtained with informed consent and ethical

approval by an institutional review board that complies with all

principles of the Helsinki Accord (Western IRB Study no. 20040468).

Genomic DNA was extracted from peripheral blood lymphocytes

using standard procedures or from saliva collected in an Oragene

DNA sample collection kit (DNA Genotek, Ontario, Canada) and

extracted according to the manufacturer’s protocol.

Mutation detection

The coding regions of KRT6A, KRT6B, KRT16, and KRT17 were

amplified using primers specific to the respective functional genes to

avoid amplification of KRT6C or pseudogenes (Supplementary Table

S2 online). All primers were checked for single-nucleotide poly-

morphisms using Diagnostic SNPCheck (http://www.ngrl.org.uk/

Manchester) and some were modified from our previous publica-

tions (Smith et al., 2005) to increase specificity. For each gene, there

are two primer sets for the mutation hotspot exons to overcome the

potential problem of very rare or as yet unidentified single-

nucleotide polymorphisms in primers designed to amplify these

regions. Previously unreported mutations were excluded from at

least 90 control DNA samples (180 chromosomes) by sequencing or

restriction enzyme digests. For full-length genomic PCR reactions,

Takara buffer and LA Taq polymerase (Lonza Biologics PLC, Slough,

UK) were used and for the smaller PCR reactions and HotStarTaq

DNA Polymerase and buffer system (Qiagen, Crawley, UK) were

used according to the manufacturer’s instructions. Specific PCR

conditions for each primer set are available on request. PCR

products were purified using QiaQuick PCR spin columns (Qiagen)

or ExoSAP (using Exonuclease 1 and Shrimp Antartic Phosphatase,

New England Biolabs, Hitchin, Herts, UK), and sequenced using

internal primers on an ABI 3100 Automated DNA sequencing

machine (Applied Biosystems, Foster City, CA) according to the

manufacturer’s instructions.

Protein bioinformatics

Hydrophobicity (Kyte–Doolittle analysis) and protein secondary

structure predictions (Robson–Garnier analysis) were performed

using the Protein Analysis Toolkit function within the MacVector

9.0 software package (MacVector, Cary, NC).

CONFLICT OF INTERESTThe authors state no conflict of interest.

ACKNOWLEDGMENTSWe thank the many patients, their families, clinical care providers, and thereferring physicians, Dr Anneli Bowen, University of Utah; Dr Roman Carlos,Guatemala; Dr Bernard Cohen, Johns Hopkins Medical Center, Baltimore; DrGiselly De Crignis, Brazil; Dr Loretta Fiorillo, Alberta, Canada; Dr WataruFujimoto, Okayama, Japan; Dr Ramon Grimalt, Barcelona, Spain; Dr AnnaHogendorf, Lodz, Poland; Dr Edel O’Toole, Barts and the London, QueenMary’s School of Medicine and Dentistry, London, UK; Dr Birget Schulze,Frankfurt, Germany; Dr Michael Sorace, UCLA Department of Dermatology,LA; Dr Jose Suarez, Canary Islands, Spain; Dr Yasushi Suga, JuntendoUniversity School of Medicine, Japan; Dr Jean Y. Tang, Stanford University, CA;Dr Maurice A.M. van Steensel, University Hospital Maastricht, The Netherlands,and Dr Mary Williams, UCSF, Department of Dermatology, San Francisco, CA,without whose participation and continued support, this study would not havebeen possible. We also thank Holly Evans for her help with data preparation.FJDS and NJW are supported by research grants from PC Project.

SUPPLEMENTARY MATERIAL

Supplementary material is linked to the online version of the paper at http://www.nature.com/jid

REFERENCES

Betz RC, Planko L, Eigelshoven S et al. (2006) Loss-of-function mutations inthe keratin 5 gene lead to Dowling-Degos disease. Am J Hum Genet

78:510–9

Bowden PE, Haley JL, Kansky A et al. (1995) Mutation of a type II keratin gene(K6a) in pachyonychia congenita. Nat Genet 10:363–5

Cogulu O, Onay H, Aykut A et al. (2009) Pachyonychia congenita type 2,N92S mutation of keratin 17 gene: clinical features, mutation analysis

and pathological view. Eur J Pediatr 168:1269–72

Eliason MJ, Leachman SA, Feng BJ et al. (2011) A review of the clinicalphenotype in 254 patients with genetically-confirmed pachyonychia

congenita. JAAD (unpublished)

Frischmeyer PA, Dietz HC (1999) Nonsense-mediated mRNA decay in healthand disease. Hum Mol Genet 8:1893–900

Fu T, Leachman SA, Wilson NJ et al. (2011) Genotype-phenotype correlationsamong pachyonychia congenita patients with K16 mutations. J Invest

Dermatol (this issue)

Gruber R, Wilson NJ, Smith FJ et al. (2009) Increased pachyonychia congenitaseverity in patients with concurrent keratin and filaggrin mutations.

Br J Dermatol 161:1391–5

Ishida-Yamamoto A, Kato H, Kiyama H et al. (2000) Mutant loricrin is notcrosslinked into the cornified cell envelope but is translocated into the

nucleus in loricrin keratoderma. J Invest Dermatol 115:1088–94

Jackson ADM, Lawler SD (1951) Pachyonychia congenita: a report of sixcases in one family with a note on linkage data. Ann Eugen 16:142–6

Jadassohn J, Lewandowski F (1906) [Pachyonychia congenita: keratosisdisseminata circumscripta (follicularis). Tylomata. Leukokeratosis lin-

guae.]. Vol. 1. Berlin: Urban and Schwarzenberg, 29

Korge BP, Gan S-Q, McBride OW et al. (1992) Extensive size polymorphismof the human keratin 10 chain resides in the C-terminal V2 subdomain

due to variable numbers and sizes of glycine loops. Proc Natl Acad SciUSA 89:910–4

Lamartine J, Munhoz Essenfelder G, Kibar Z et al. (2000) Mutations in GJB6cause hidrotic ectodermal dysplasia. Nat Genet 26:142–4

Lane EB (1993) Keratins. In: Connective Tissue and its Heritable Disorders.

Molecular, Genetic and Medical Aspects. (Royce PM, Steinmann B, eds).New York: Wiley-Liss, 237–47

Leachman SA, Kaspar RL, Fleckman P et al. (2005) Clinical and pathological

features of pachyonychia congenita. J Investig Dermatol Symp Proc10:3–17

Liao H, Sayers JM, Wilson NJ et al. (2007a) A spectrum of mutations in

keratins K6a, K16 and K17 causing pachyonychia congenita. J DermatolSci 48:199–205

Liao H, Zhao Y, Baty DU et al. (2007b) A heterozygous frameshift mutationin the V1 domain of keratin 5 in a family with Dowling-Degos disease.

J Invest Dermatol 127:298–300

Livingston RJ, Sybert VP, Smith LT et al. (2001) Expression of a truncatedkeratin 5 may contribute to severe palmar – plantar hyperkeratosis in

epidermolysis bullosa simplex patients. J Invest Dermatol 116:970–4

Lugassy J, Itin P, Ishida-Yamamoto A et al. (2006) Naegeli-Franceschetti-Jadassohn syndrome and dermatopathia pigmentosa reticularis: two

allelic ectodermal dysplasias caused by dominant mutations in KRT14.Am J Hum Genet 79:724–30

McLean WH, Irvine AD, Hamill KJ et al. (2003) An unusual N-terminaldeletion of the laminin alpha3a isoform leads to the chronic granulation

tissue disorder laryngo-onycho-cutaneous syndrome. Hum Mol Genet12:2395–409

McLean WHI, Hansen CD, Eliason M et al. (2011) The phenotypic and

molecular genetic features of pachyonychia congenita. J Invest Dermatol(this issue)



http://www.ngrl.org.uk/Manchester

http://www.ngrl.org.uk/Manchester

http://www.nature.com/jid

http://www.nature.com/jid

McLean WH, Rugg EL, Lunny DP et al. (1995) Keratin 16 and keratin 17mutations cause pachyonychia congenita. Nat Genet 9:273–8

Mettler G, Fraser FC (2000) Recurrence risk for sibs of children with‘‘sporadic’’ achondroplasia. Am J Med Genet 90:250–1

Muller FB, Anton-Lamprecht I, Kuster W et al. (1999) A premature stop codonmutation in the 2B helix termination peptide of keratin 5 in a Germanepidermolysis bullosa simplex Dowling-Meara case. J Invest Dermatol112:988–90

Oh Adib C, Jones B, Liao H et al. (2008) Recurrent mutation in keratin 17 in alarge family with pachyonychia congenita type 2. Arch Dermatol Res300:211–4

Pfendner EG, Sadowski SG, Uitto J (2005) Epidermolysis bullosa simplex:recurrent and de novo mutations in the KRT5 and KRT14 genes,phenotype/genotype correlations, and implications for genetic counsel-ing and prenatal diagnosis. J Invest Dermatol 125:239–43

Richardson ES, Lee JB, Hyde PH et al. (2006) A novel mutation and large sizepolymorphism affecting the V2 domain of keratin 1 in an African-American family with severe, diffuse palmoplantar keratoderma of theichthyosis hystrix Curth-Macklin type. J Invest Dermatol 126:79–84

Rugg EL, Rachet-Prehu MO, Rochat A et al. (1999) Donor splice site mutationin keratin 5 causes in-frame removal of 22 amino acids of H1 and 1A roddomains in Dowling-Meara epidermolysis bullosa simplex. Eur J HumGenet 7:293–300

Smith FJ, Liao H, Cassidy AJ et al. (2005) The genetic basis of pachyonychiacongenita. J Investig Dermatol Symp Proc 10:21–30

Smith FJ, Morley SM, McLean WH (2002) A novel connexin 30 mutation inClouston syndrome. J Invest Dermatol 118:530–2

Smith FJD, Corden LD, Rugg EL et al. (1997) Missense mutations inkeratin 17 cause either pachyonychia congenita type 2 or aphenotype resembling steatocystoma multiplex. J Invest Dermatol108:220–3

Smith FJD, Fisher MP, Healy E et al. (2000) Novel keratin 16 mutations andprotein expression studies in pachyonychia congenita type 1 and focalpalmoplantar keratoderma. Exp Dermatol 9:170–7

Smith FJD, Jonkman MF, van Goor H et al. (1998) A mutation in humankeratin K6b produces a phenocopy of the K17 disorder pachyonychiacongenita type 2. Hum Mol Genet 7:1143–8

Sprecher E, Ishida-Yamamoto A, Becker OM et al. (2001) Evidence for novelfunctions of the keratin tail emerging from a mutation causing ichthyosishystrix. J Invest Dermatol 116:511–9

Sprecher E, Yosipovitch G, Bergman R et al. (2003) Epidermolytichyperkeratosis and epidermolysis bullosa simplex caused by frameshiftmutations altering the v2 tail domains of keratin 1 and keratin 5. J InvestDermatol 120:623–6

Szeverenyi I, Cassidy AJ, Chung CW et al. (2008) The Human IntermediateFilament Database: comprehensive information on a gene familyinvolved in many human diseases. Hum Mutat 29:351–60

Terron-Kwiatkowski A, Paller AS, Compton J et al. (2002) Two cases ofprimarily palmoplantar keratoderma associated with novel mutations inkeratin 1. J Invest Dermatol 119:966–71

van Steensel MAM, Jonkman MF, van Geel M et al. (2003) Clouston syndromecan mimic pachyonychia congenita. J Invest Dermatol 121:1035–8

Wilson NJ, Messenger AG, Leachman SA et al. (2010) Keratin K6c mutationscause focal palmoplantar keratoderma. J Invest Dermatol 130:425–9

www.jidonline.org 7



GENETICSBJD

British Journal of Dermatology

The molecular genetic analysis of the expandingpachyonychia congenita case collectionN.J. Wilson,1 E.A. O’Toole,2 L.M. Milstone,3 C.D. Hansen,4 A.A. Shepherd,1 E. Al-Asadi,1 M.E. Schwartz,5

W.H.I. McLean,1 E. Sprecher6 and F.J.D. Smith1

1Centre for Dermatology and Genetic Medicine, Colleges of Life Sciences and Medicine, Dentistry & Nursing, University of Dundee, Dundee, DD1 5EH, U.K.2Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, U.K.3Department of Dermatology, Yale University, New Haven, CT, U.S.A.4Department of Dermatology, University of Utah, Salt Lake City, UT, U.S.A.5PC Project, Salt Lake City, UT, U.S.A.6Tel Aviv Sourasky Medical Center, Tel Aviv, Israel

CorrespondenceFrances J.D. Smith

E-mail: [email protected]

Accepted for publication

4 March 2014

Funding sourcesF.J.D.S. and N.J.W. are supported by a grant

from the Pachyonychia Congenita Project www.

pachyonychia.org (to F.J.D.S.). The Centre for

Dermatology and Genetic Medicine at the

University of Dundee is supported by a Wellcome

Trust Strategic Award (098439/Z/12/Z to

W.H.I.M.).

Conflicts of interest

None declared.

DOI 10.1111/bjd.12958

Summary

Background Pachyonychia congenita (PC) is a rare autosomal dominant keratinizingdisorder characterized by severe, painful, palmoplantar keratoderma and nail dys-trophy, often accompanied by oral leucokeratosis, cysts and follicular keratosis. Itis caused by mutations in one of five keratin genes: KRT6A, KRT6B, KRT6C, KRT16or KRT17.Objectives To identify mutations in 84 new families with a clinical diagnosis ofPC, recruited by the International Pachyonychia Congenita Research Registry dur-ing the last few years.Methods Genomic DNA isolated from saliva or peripheral blood leucocytes wasamplified using primers specific for the PC-associated keratin genes and polymer-ase chain reaction products were directly sequenced.Results Mutations were identified in 84 families in the PC-associated keratin genes,comprising 46 distinct keratin mutations. Fourteen were previously unreportedmutations, bringing the total number of different keratin mutations associatedwith PC to 105.Conclusions By identifying mutations in KRT6A, KRT6B, KRT6C, KRT16 or KRT17, thisstudy has confirmed, at the molecular level, the clinical diagnosis of PC in thesefamilies.

What’s already known about this topic?

• Pachyonychia congenita (PC) is caused by autosomal dominant mutations in KRT6A,

KRT6B, KRT6C, KRT16 or KRT17.

• Plantar pain is the main symptom.

• Palmoplantar keratoderma and nail dystrophy are the predominant characteristics,

often accompanied by oral leucokeratosis, cysts and follicular keratosis.

What does this study add?

• This study identifies PC-associated keratin mutations in 84 new families with PC

recruited by the International Pachyonychia Congenita Research Registry.

• Fourteen of the 46 distinct keratin mutations were previously unreported.

• This study expands the large well-phenotyped and genotyped case series of patients

with PC, which is an invaluable resource for the development of mutation-specific

and/or gene-specific therapies and for future clinical trials.

© 2014 The Authors. British Journal of Dermatologypublished by John Wiley & Sons Ltd on behalf of British Association of Dermatologists

British Journal of Dermatology (2014) 171, pp343–355 343

This is an open access article under the terms of the Creative Commons Attribution License, which permits use,distribution and reproduction in any medium, provided the original work is properly cited.

Pachyonychia congenita (PC, OMIM #167200 and #167210)

is a rare autosomal dominant disorder of keratinization, with

hallmark signs of palmoplantar keratoderma (PPK) and nail

dystrophy (Fig. 1). The main symptom is plantar pain. Addi-

tional characteristics include oral leucokeratosis; cysts of

various types, including epidermal inclusion cysts and pilo-

sebaceous cysts; follicular keratoses; hoarseness; hyperhidrosis;

and natal teeth. The severity and clinical features can vary, as

shown in Figure 1. While clinical case reports of PC date back

to 1906,1 and possibly earlier, the understanding behind the

K6a p.Glu472Lys K6b p.Glu472Lys

K6a p.Asn172del K16 p.Leu132Pro

K17 p.Asn92Ser K17 p.Met88Lys

K17 p.Met88Lys

K16 p.Leu132Pro

K17 p.Asn92Ser

K16 p.Ser130del

K6a p.Ile178Asn

K6a p.Asn172del

Fig 1. Clinical features of pachyonychia congenita (PC). Palmoplantar keratoderma, nail dystrophy, oral leukokeratosis and cysts in patients with

PC with identified mutations.


British Journal of Dermatology (2014) 171, pp343–355

344 Mutations in pachyonychia congenita, N.J. Wilson et al.

genetic basis of PC was not elucidated until 1994,2 following

discoveries resulting in epidermolysis bullosa simplex (EBS)

being the first keratin disorder for which the molecular basis

was identified.3–5 Mutations in one of five keratin genes –

KRT6A, KRT6B, KRT6C, KRT16 or KRT17 – are now known to

cause PC.6–9 Formerly classified as PC-1 (caused by mutations

in KRT6A or KRT16) and PC-2 (due to mutations in KRT6B or

KRT17), PC nomenclature has recently been revised based on

the molecular genetic data; for example, those with mutations

in KRT6A are named PC-K6a and those with KRT16 mutations

are PC-K16.10

Keratins comprise the type I and type II groups of the inter-

mediate filament subgroup of cytoskeletal proteins. The 54

known functional keratin genes are divided into epithelial and

hair keratins.11,12 Keratin proteins, albeit very diverse in func-

tion, all share a similar protein structure consisting of an a-heli-cal central rod domain comprising four domains (1A, 1B, 2A,

2B) connected by nonhelical regions (L1, L12, L2).13 The

majority of mutations causing PC are at the start and end of the

a-helical rod domain (within 1A and 2B) within the helix

boundary motif domains that show evolutionary conservation

throughout all intermediate filaments. These motif regions are

thought to play a vital role in the interaction of filaments during

cytoskeleton construction in forming end–end overlap inter-

actions during filament assembly.14

More than 20 keratin genes are now known to cause

directly or predispose to fragility syndromes (www.interfil.

org), emphasizing the importance of keratins in skin and epi-

thelial appendages. Keratin diseases are almost always inherited

in an autosomal dominant manner where mutations act in a

dominant negative way, disrupting the ability of keratin fila-

ments to form a strong cytoskeleton, leaving the skin in a

fragile, unprotected condition unable to withstand trauma.

The mutational spectrum covers all types (missense mutations,

small deletion/insertion mutations, splice-site mutations and

nonsense mutations), and the disease produced is confined

strictly to the epithelial site where the mutant keratin protein

is normally expressed; for example, keratin K6a is expressed

in palmoplantar epidermis, nail epithelia and mucosal tissues

– the tissues affected in PC.

The International Pachyonychia Congenita Research Registry

(IPCRR) has, to date, collected clinical and molecular data from

more than 500 patients with PC and their families (~270 fami-

lies) worldwide. Here, we report molecular analysis of 84 fami-

lies registered within the last few years of this expanding case

collection with a clinical diagnosis of PC. Mutations were identi-

fied in KRT6A, KRT6B, KRT6C, KRT16 or KRT17. Forty-six distinct

keratin mutations were found, 14 of which were previously

unreported mutations, bringing the total number of different

keratin mutations associated with PC to 105.

Materials and methods

Genomic DNA was extracted from saliva collected in an

Oragene DNA sample collection kit (DNA Genotek, Kanata,

ON, Canada) and extracted according to the manufacturer’s

protocol or from peripheral blood leucocytes using standard

procedures. Samples were obtained by the IPCRR with

informed consent and ethical approval from Western Institu-

tional Review Board (IRB), which complies with all principles

of the Declaration of Helsinki (Western IRB study no.

20040468).

Mutation detection

The coding regions of KRT6A, KRT6, KRT6C, KRT16 and KRT17

were amplified using primers specific to the respective func-

tional genes and to avoid amplification of K16/K17 pseudo-

genes. All primers were checked for single nucleotide polymor-

phisms using Diagnostic SNPCheck (www.ngrl.org.uk/

Manchester), and some have been modified since our previous

publications to increase specificity (Table S1).9,15,16 For ampli-

fication of larger fragments, Takara LA Taq polymerase and

buffer (Takara Bio Europe/Clontech, 78100 Saint-Germain-

en-Laye, France) was used; for smaller polymerase chain reac-

tion (PCR) reactions, HotStarTaq DNA Polymerase and buffer

system (Qiagen, Crawley, U.K.) was used according to the man-

ufacturer’s instructions. Specific PCR conditions for each primer

set are available on request. PCR products were purified using

QiaQuick PCR spin columns (Qiagen) or ExoSAP (using exonu-

clease 1 and shrimp antartic phosphatase) and sequenced using

internal primers on an ABI 3700 Automated DNA sequencing

machine (Applied Biosystems, Foster City, CA, U.S.A.). Previ-

ously unreported mutations were excluded from at least 90 con-

trol DNA samples (180 chromosomes) by sequencing or

restriction enzyme digests. The occurrence of sequence changes

was also checked on the Exome Variant Server (http://evs.gs.

washington.edu/EVS) and dbSNP database.

RNA extraction

A 3-mm punch biopsy was taken from an affected individual

from family 17 with splice-site mutation K6a c.541–2A>Gand put in RNAlater (Life Technologies, Paisley, U.K.). mRNA

was extracted using a Quick Prep Micro mRNA purification kit

(GE Healthcare UK, Little Chalfont, U.K.) and reverse tran-

scribed using AMV Reverse Transcriptase (Promega, South-

ampton, U.K.). cDNA was amplified using the Expand High

Fidelity PCR system (Roche, Mannheim, Germany) with prim-

ers specific for K6a within exon 1 through exon 5.

Cloning of polymerase chain reaction fragments

The splice-site mutation K6a c.541–2A>G was confirmed by

cloning the PCR product derived from cDNA (above) into

pCR2.1 vector (TA cloning kit; Life Technologies). Several

independent clones were sequenced.

K16 constructs and transfections

Full-length K16 cDNA was cloned into expression vector

pCR3.1 (Life Technologies) and used as a template for site-



Mutations in pachyonychia congenita, N.J. Wilson et al. 345

directed mutagenesis (Stratagene, Cedar Creek, TX, U.S.A.) to

make constructs containing K16 p.Arg418Cys and K16

p.Arg418Pro. The three plasmids were transfected individually

into PtK2 cells using Lipofectamine 2000 (Life Technologies),

according to the manufacturer’s protocol. Cells were fixed at 48

and 72 h post-transfection in 1 : 1 methanol : acetone for

5 min, air dried and double-label immunofluorescence was per-

formed. Transfected K16 was detected with rabbit polyclonal

antisera (1 : 500 dilution) against human K16 (gift of Pierre

Coulombe, Johns Hopkins University, Baltimore, MD, U.S.A.)

and the endogenous K8 with neat supernatant monoclonal anti-

body LE41 to PtK2 K8 (gift of Birgitte Lane, Institute of Medical

Biology, Immunos, Singapore). Alexafluor 488 goat anti-mouse

and Alexafluor 594 goat anti-rabbit secondary antibodies (Life

Technologies) were used at a dilution of 1 : 1000. Nuclei were

stained with 40,6-diamidino-2-phenylindole (DAPI).

Results

Clinical details

The main clinical features of individuals involved in this study

are reported in Table 1. All cases were recruited through the

IPCRR, an ongoing research programme to identify patients

with PC worldwide and to collect detailed clinical and molecu-

lar data from all individuals registered. Autosomal dominant

inheritance was observed in 49 of 84 families, while the

remaining cases were apparently due to spontaneous muta-

tions. In many cases with previously reported mutations the

parents were not screened.

Mutation analysis

Of the 84 families, we identified previously unreported het-

erozygous mutations in 14 of them and known heterozygous

mutations in 70 families. The majority were missense muta-

tions, with the remainder being small in-frame deletion,

frameshift, nonsense or splice-site mutations in KRT6A, KRT6B,

KRT6C, KRT16 or KRT17 (Table 1).

Mutations in KRT6A (PC-K6a)

Thirty-one families had mutations in KRT6A and of the 18 dif-

ferent mutations, four, including a nonsense mutation, were

previously unreported. The most commonly reported mutation

in PC is K6a p.Asn172del, found in 10 families here, and

overall in ~30% of kindreds with mutations in K6a and in

~13% of all families with a PC mutation (including published,

www.interfil.org, and those reported here).

A novel missense mutation, K6a p.Phe174Ile, was identified

in family 13; other amino acid substitutions at this residue

have been reported, p.Phe174Ser in at least 12 families,

including one in this study, and p.Phe174Cys in one family.17

Mutation K6a p.Glu473GlyfsTer91 (family 30), an

unreported frameshift mutation at the end of the 2B domain of

K6a, is due to duplication of a single ‘G’ nucleotide,

c.1417dupG. This results in a frameshift starting with codon

473, which is changed from glutamic acid to a glycine residue

and creates a premature stop codon at position 91 of the new

reading frame; this is predicted to cause loss of normal protein

function through protein truncation. Specifically, the last 92 cor-

rect amino acids are replaced by 90 incorrect amino acids, which

are very different in sequence leading to a foreign protein

(Fig. 2). A previously reported mutation, K6a p.Ser505Glnf-

sTer59, downstream of the above mutation, also resulted in a 1-

bp insertion,16 this time in the V2 domain, and the resulting 58

foreign amino acids were the same as in the above mutation.

A previously unreported nonsense mutation, K6a p.Glu461-

Ter (in Family 21) at the start of the helix termination motif

in the 2B domain of K6a, results in a premature stop codon

leading to a truncated protein lacking the helix termination

motif and tail domain. Missense mutations have previously

been reported at this position: K6a p.Glu461, p.Glu461Lys

and p.Glu461Gln (www.interfil.org).

Splice-site mutations were found in six families in KRT6A.

In five of these (families 16–20) mutations were at the intron

1/exon 2 boundary of K6a; three different sequence changes

were identified, all of which we have reported previously,16

but at that time, owing to the unavailability of mRNA, we

were unable to identify the mutations at the protein level.

However, in this study we obtained mRNA from a skin biopsy

from an affected individual from family 17 with mutation K6a

c.541–2A>G. The resulting cDNA was amplified by PCR and

cloned, and several clones were sequenced to identify the con-

sequence of this mutation. The mutation is predicted to result

in an in-frame deletion of the first six amino acids of exon 2,

K6a p. Val181_Gln186del. mRNA was unavailable from other

families with the different sequence changes at this splice site.

In a sixth family (family 31) a previously unreported splice-

site mutation was identified at the exon 8/intron 9 boundary

(c.1460–1G>C); unfortunately, we were unable to obtain

mRNA from this family to determine the effect of this geno-

mic mutation on RNA splicing.

Mutations in KRT6B (PC-K6b)

Mutations in KRT6B were found in nine families, of which one

was novel. Only three different mutations have previously

been reported in KRT6B17 (www.interfil.org): p.Asn172del,

p.Glu461Lys and p.Glu472Lys. Here, eight of the nine families

with mutations in KRT6B had mutations at these sites, further

indicating that these are mutation hotspot residues in KRT6B:

p.Asn172del (families 32–35), p.Glu461Lys (family 36) and

p.Glu472Lys (families 38–40). Family 37 was found to have

an unreported missense mutation within the 2B domain of

KRT6B, p.Leu469Arg. The analogous mutation has been

reported in KRT6A (www.interfil.org).

Mutations in KRT6C (PC-K6c)

Only two families (families 41 and 42) had mutations in

KRT6C, both with the same known mutation, p.Glu472Lys.




Table

1Mutations

andclinicaldetails

innew

casesof

pachyonychia

cong

enita

Family

Mutation–protein

change

DNAchange

Unreported

orknow

nFamilialor

spon

taneou

sPlantarpain

Palm

oplantar

keratoderm

aThickened

nails

Oral

leucokeratosis

Cystsand/

or

follicular

hyperkeratosis

Born

with

teeth?

1K6a

p.Glu16

3Lys

c.48

7G>A

Kno

wn

Familial

Somew

hatpainful

PPK

All20

Yes

NA

No

2K6a

p.Leu1

70Phe

c.50

8C>T

Kno

wn

Spon

taneou

sNot

painful

PPK,very

mild

All20

No

NA

No

3K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PKAll20

No

NA

No

4K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

All20

Yes

NA

No

5K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Spon

taneou

sNA;un

der2yearsold

NA;un

der

2yearsold

10fing

ernails,

2toenails

Yes

NA

No

6K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PPK

All20

Yes

Pilosebaceou

s,

follicular

hyperkeratosis

No

7K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PPK

All20

Yes

Steatocystom

a,pilosebaceou

s,

follicular

hyperkeratosis

No

8K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Spon

taneou

sSomew

hatpainful

PPK

All20

Yes

Steatocystom

a,follicular

hyperkeratosis

No

9K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Not

painful

PPK

All20

Yes

Follicular

hyperkeratosis

No

10K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Spon

taneou

sOften

requ

ires

medication

tohand

lethepain

PPK

All20

Yes

NA

No

11K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Spon

taneou

sSomew

hatpainful

PPK

All20

Yes

NA

No

12K6a

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Often

requ

ires

medication

tohand

lethepain

PPK

All20

Yes

Follicular

hyperkeratosis

No

13K6a

p.Phe174

Ile

c.52

0T>A

Unreported

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PKAll20

Yes

Pilosebaceou

s,follicular

hyperkeratosis

No

14K6a

p.Phe174

Ser

c.52

1T>C

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PKAll20

Yes

NA

No

15K6a

p.Ile178

Asn

c.53

3T>A

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PKAll20

Yes

Pilosebaceou

s,

follicular

hyperkeratosis

No

16ND

c.54

1–1G

>C

Kno

wn

Familial

Often

requ

ires

medication

tohand

lethepain

PK6fing

ernails,

10toenails

Yes

NA

No

17K6a

p.Val18

1_Gln18

6del

c.54

1–2A

>G

Kno

wn

Familial

Somew

hatpainful

PKAll20

Yes

Pilosebaceou

s,

follicular

hyperkeratosis

No




Table

1(con

tinu

ed)

Family

Mutation–protein

change

DNAchange

Unreported

orknow

nFamilialor

spon

taneou

sPlantarpain

Palm

oplantar

keratoderm

aThickened

nails

Oral

leucokeratosis

Cystsand/

or

follicular

hyperkeratosis

Born

with

teeth?

18K6a

p.Val18

1_Gln18

6del

c.54

1–2A

>G

Kno

wn

Familial

Verypainful,bu

tdo

esno

tusemedication

PPK

All20

Yes

Pilosebaceou

s,follicular

hyperkeratosis

No

19K6a

p.Val18

1_Gln18

6del

c.54

1–2A

>G

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PKAll20

Yes

NA

No

20ND

c.54

1–2A

>C

Kno

wn

Spon

taneou

sSomew

hatpainful

PK5fing

ernails,

10toenails

Yes

NA

No

21K6a

p.Glu46

1Ter

c.13

81G>T

Unreported

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PK5fing

ernails,

10toenails

Yes

Steatocystom

a,

pilosebaceou

s,follicular

hyperkeratosis

No

22K6a

p.Ile462

Asn

c.13

85T>A

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PKAll20

Yes

Pilosebaceou

s,follicular

hyperkeratosis

No

23K6a

p.Ala46

3Pro

c.13

87G>C

Kno

wn

Spon

taneou

sSomew

hatpainful

PPK

All20

Yes

Follicular

hyperkeratosis

No

24K6a

p.Thr46

4Pro

c.13

90A>C

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PKAll20

Yes

Follicular

hyperkeratosis

No

25K6a

p.Leu4

68Pro

c.14

03T>C

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PPK

All20

Yes

Follicular

hyperkeratosis

No

26K6a

p.Leu4

69Pro

c.14

06T>C

Kno

wn

Familial

Often

requ

ires

medication

tohand

lethepain

PPK

All20

Yes

Steatocystom

a,

pilosebaceou

s

No

27K6a

p.Leu4

69Pro

c.14

06T>C

Kno

wn

Spon

taneou

sOften

requ

ires

medication

tohand

lethepain

PPK

All20

Yes

Follicular

hyperkeratosis

No

28K6a

p.Glu47

2Lys

c.14

14G>A

Kno

wn

Spon

taneou

sNot

painful(und

er3years)

PKAll20

No

Smallredbu

mps

andoccasion

alspotson

hisface,

butthey

couldbe

standard

baby

acne

No

29K6a

p.Glu47

2Lys

c.14

14G>A

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PPK

All20

Yes

Steatocystom

a,pilosebaceou

s,

follicular

hyperkeratosis

No

30K6a

p.Glu47

3GlyfsTer91

c.14

17du

pGUnreported

Spon

taneou

sSomew

hatpainful

PPK

10fing

ernails,

7toenails

Yes

NA

No

31ND

c.14

60–1

G>C

Unreported

Familial

Often

requ

ires

medication

tohand

lethepain

PPK

2fing

ernails,

10toenails

No

NA

No

32K6b

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Somew

hatpainful

PK10

fing

ernails,

7toenails

Yes

NA

No




Table

1(con

tinu

ed)

Family

Mutation–protein

change

DNAchange

Unreported

orknow

nFamilialor

spon

taneou

sPlantarpain

Palm

oplantar

keratoderm

aThickened

nails

Oral

leucokeratosis

Cystsand/

or

follicular

hyperkeratosis

Born

with

teeth?

33K6b

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

6fing

ernails,

10toenails

Yes

Steatocystom

a,

pilosebaceou

s

No

34K6b

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PK6fing

ernails,

10toenails

No

Pilosebaceou

s,

follicular

hyperkeratosis

No

35K6b

p.Asn17

2del

c.51

6_51

8delCAA

Kno

wn

Familial

Somew

hatpainful

PPK

8fing

ernails,

10toenails

No

Pilosebaceou

s,follicular

hyperkeratosis

No

36K6b

Glu46

1Lys

c.13

81G>A

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PPK

7toenails

Yes

Follicular

hyperkeratosis

No

37K6b

p.Leu4

69Arg

c.14

06T>

GUnreported

Spon

taneou

sSomew

hatpainful

PK6toenails

Yes

Follicular

hyperkeratosis

No

38K6b

p.Glu47

2Lys

c.14

14G>A

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PK8toenails

Yes

NA

No

39K6b

p.Glu47

2Lys

c.14

14G>A

Kno

wn

Familial

Somew

hatpainful

PK4toenails

No

Steatocystom

a,

pilosebaceou

s,follicular

hyperkeratosis

No

40K6b

p.Glu47

2Lys

c.14

14G>A

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PPK

9toenails

No

Steatocystom

aNo

41K6c

p.Glu47

2Lys

c.14

14G>A

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

4toenails

Yes

Steatocystom

a,

pilosebaceou

s

No

42K6c

p.Glu47

2Lys

c.14

14G>A

Kno

wn

Familial

Somew

hatpainful

PK2toenails

No

NA

No

43K16

p.Met12

1Lys

c.36

2T>A

Kno

wn

Familial

Verypainful,bu

tdo

esno

tusemedication

PPK

All20

No

NA

No

44K16

p.Met12

1Thr

c.36

2T>C

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PK4toenails

No

NA

No

45K16

p.Leu1

24His

c.37

1T>A

Kno

wn

Familial

Verypainful,bu

tdo

esno

tusemedication

PPK

6fing

ernails,

10toenails

No

NA

No

46K16

p.Leu1

24His

c.37

1T>A

Kno

wn

Familial

Verypainful,bu

tdo

esno

tusemedication

PPK

5toenails

No

NA

No

47K16

p.Asn12

5Asp

c.37

3A>G

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

10toenails

No

Pilosebaceou

sNo

48K16

p.Asn12

5Ser

c.37

4A>G

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

es

notusemedication

PPK

All20

No

NA

No

49K16

p.Asn12

5Ser

c.37

4A>G

Kno

wn

Spon

taneou

sSomew

hatpainful;on

ly

6yearsold

PK2toenails

No

NA

No

50K16

p.Asn12

5Ser

c.37

4A>G

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

3toenails

Yes

NA

No




Table

1(con

tinu

ed)

Family

Mutation–protein

change

DNAchange

Unreported

orknow

n

Familialor

spon

taneou

sPlantarpain

Palm

oplantar

keratoderm

a

Thickened

nails

Oral

leucokeratosis

Cystsand/

orfollicular

hyperkeratosis

Born

with

teeth?

51K16

p.Asn12

5Ser

c.37

4A>G

Kno

wn

Familial

Somew

hatpainful

PPK

8toenails

No

NA

No

52K16

p.Asn12

5Ser

c.37

4A>G

Kno

wn

Spon

taneou

sSomew

hatpainful

PPK

2toenails

No

Follicular

hyperkeratosis

No

53K16

p.Asn12

5Ser

c.37

4A>G

Kno

wn

Familial

Often

requ

ires

medication

tohand

lethepain

PPK

All20

Yes

Follicular

hyperkeratosis

No

54K16

p.Arg12

7Pro

c.38

0G>C

Kno

wn

Familial

Somew

hatpainful

PPK

All20

No

Follicular

hyperkeratosis

No

55K16

p.Arg12

7Gly

c.37

9C>G

Unreported

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

All20

No

Steatocystom

aNo

56K16

p.Arg12

7Cys

c.37

9C>T

Kno

wn

Familial

Often

requ

ires

medication

tohand

lethepain

PK5toenails

No

Follicular

hyperkeratosis

No

57K16

p.Arg12

7Cys

c.37

9C>T

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

2toenails

Yes

NA

No

58K16

p.Arg12

7Cys

c.37

9C>T

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

3toenails

No

NA

No

59K16

p.Arg12

7Cys

c.37

9C>T

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

Non

eNo

NA

No

60K16

p.Arg12

7Cys

c.37

9C>T

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PK6toenails

No

NA

No

61K16

p.Arg12

7Ser

c.37

9C>A

Unreported

Familial

Often

requ

ires

medication

tohand

lethepain

PK7toenails

No

NA

No

62K16

p.Arg12

7His

c.38

1G>A

Unreported

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

4toenails

Yes

Pilosebaceou

s,

follicular

hyperkeratosis

No

63K16

p.Ser130

del

c.38

9–39

1delCCT

Kno

wn

Familial

Often

requ

ires

medication

tohand

lethepain

PPK

All20

No

Follicular

hyperkeratosis

No

64K16

p.Leu1

32Pro

c.39

5T>C

Kno

wn

Familial

Verypainful,bu

tdo

esno

tusemedication

PPK

All20

No

NA

No

65K16

p.Arg41

8Pro

c.12

53G>C

Unreported

Familial

Verypainful,bu

tdo

esno

tusemedication

PK2toenails

No

NA

No

66K16

p.Arg41

8_Arg41

9del

c.12

53_1

258d

elGCCGCC

Unreported

Familial

Verypainful,bu

tdo

esno

tusemedication

PPK

2fing

ernails,

3toenails

Yes

NA

No

67K17

p.Met88

Lys

c.26

3T>A

Kno

wn

Spon

taneou

sNA

Non

e(und

er3yearsof

age)

All20

No

Follicular

hyperkeratosis

Yes




Table

1(con

tinu

ed)

Family

Mutation–protein

change

DNAchange

Unreported

orknow

nFamilialor

spon

taneou

sPlantarpain

Palm

oplantar

keratoderm

aThickened

nails

Oral

leucokeratosis

Cystsand/

or

follicular

hyperkeratosis

Born

with

teeth?

68K17

p.Met88

Arg

c.26

3T>G

Unreported

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PPK

8fing

ernails,

10toenails

Yes

Steatocystom

a,pilosebaceou

s,

follicular

hyperkeratosis

No

69K17

p.Asn90

_Asp93

delin

sIle

c.26

9_27

8del10

insT

Unreported

Familial

Verypainful,bu

tdo

esno

tusemedication

PPK

All20

No

Follicular

hyperkeratosis

No

70K17

p.Leu9

1Pro

c.27

2T>C

Unreported

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PPK

All20

No

Steatocystom

a,follicular

hyperkeratosis

No

71K17

p.Asn92

Ser

c.27

5A>G

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PKAll20

No

Steatocystom

a,

pilosebaceou

s,follicular

hyperkeratosis

Yes

72K17

p.Asn92

Ser

c.27

5A>G

Kno

wn

Familial

Not

painful

PPK

6fing

ernails,

10toenails

No

Steatocystom

a,pilosebaceou

s,

follicular

hyperkeratosis

Yes

73K17

p.Asn92

Ser

c.27

5A>G

Kno

wn

Spon

taneou

sNot

painful

PPK

6fing

ernails,

10toenails

No

Steatocystom

a,pilosebaceou

sYes

74K17

p.Asn92

Ser

c.27

5A>G

Kno

wn

Spon

taneou

sOften

requ

ires

medication

tohand

lethepain

PK10

fing

ernails,

8toenails

Yes

Pilosebaceou

sNo

75K17

p.Asn92

Ser

c.27

5A>G

Kno

wn

Spon

taneou

sNA

Non

e(und

er3yearsof

age)

All20

No

NA

Yes

76K17

p.Asn92

Ser

c.27

5A>G

Kno

wn

Familial

Somew

hatpainful

PPK

6fing

ernails,

2toenails

No

Steatocystom

a,pilosebaceou

s,

follicular

hyperkeratosis

Yes

77K17

p.Asn92

Ser

c.27

5A>G

Kno

wn

Familial

Often

requ

ires

medication

tohand

lethepain

PPK

2fing

ernails,

10toenails

No

Pilosebaceou

s,follicular

hyperkeratosis

Yes

78K17

p.Arg94

Ser

c.28

0C>A

Unreported

Familial

Verypainful,bu

tdo

es

notusemedication

PK3toenails

No

Steatocystom

a,

pilosebaceou

s,follicular

hyperkeratosis

No

79K17

p.Arg94

Cys

c.28

0C>T

Kno

wn

Familial

Verypainful,bu

tdo

es

notusemedication

PPK

4toenails

No

Steatocystom

a,

pilosebaceou

s,follicular

hyperkeratosis

No




Mutations in KRT16 (PC-K16)

Mutations in KRT16 were found in 24 families; the most com-

mon recurrent mutations identified were K16 p.Asn125Ser,

p.Arg127Cys and p.Leu132Pro (www.interfil.org). Five of the

14 distinct K16 mutations were previously unreported. The

20 or more different mutations reported in keratin 16 include

p.Arg127Cys and p.Arg127Pro. In this cohort, we identified

previously unreported mutations in three families (families

55, 61 and 62) at K16 p.Arg127: p.Arg127Gly, p.Arg127Ser

and p.Arg127His. We also identified one additional family

(family 54) with mutation p.Arg127Pro and five families

(families 56–60) with p.Arg127Cys. Interestingly, the pheno-

typic variation seen with these latter two mutations indicates a

genotype–phenotype correlation, as proposed in a small

study.18 Fu et al. showed that individuals with mutation

p.Arg127Cys were more likely to have milder features of the

disorder (milder nail changes, less palmoplantar pain, etc.)

than those with amino acid substitution p.Arg127Pro.18

Including these additional mutations, ~24% of reported muta-

tions in KRT16 occur at this p.Arg127 (www.interfil.org).

Interestingly, a proline substitution for arginine was found

to be deleterious in another portion of the helix, whereas a

cysteine substitution was not. In Family 65, we identified a

new mutation K16 p.Arg418Pro. This mutation in the helix

termination motif domain of K16 is predicted to be patho-

genic. The unaffected parents of the proband were both wild

type. Another sequence change at this position, p.Arg418Cys,

which might be predicted to be pathogenic owing to its posi-

tion within the helix termination motif, is listed on the dbSNP

database (minor allele frequency from 1000 Genomes project

= 1�9%) and also on the Exome Variant Server (http://evs.gs.

washington.edu/EVS/), indicating that it may be a nonpatho-

genic sequence change. We also found p.Arg418Cys in one of

92 anonymous unrelated control DNA samples and in some

members of three unrelated PC families in which known

mutations were identified in KRT6A, KRT16 or KRT17. To inves-

tigate the effect of these sequence changes at K16 p.Arg418,

PtK2 cells were transfected with plasmids expressing either

wild-type K16, K16 p.Arg418Cys or K16 p.Arg418Pro cDNAs.

At 48 h and 72 h post-transfection cells were fixed, and

stained with a polyclonal antibody against K16 to detect trans-

fected K16. Endogenous K8 was detected with monoclonal

antibody LE41 to PtK2 K8. Nuclei were stained with DAPI.

Cells were examined for those containing filaments, filaments

plus aggregates or only aggregates. In cells transfected with

wild-type K16, 89�5% of transfected cells showed a defined

keratin cytoskeleton where wild-type K16 co-localized with

endogenous K8; the remaining 10�5% of transfected cells had

filaments plus aggregates. Cells transfected with K16

p.Arg418Cys showed a similar pattern to wild-type K16, with

89% of transfected cells with normal filament network and

11% of cells with filaments plus aggregates. However, in cells

transfected with K16 p.Arg418Pro, 98�5% of cells contained

aggregates and there was collapse/aggregation of the endoge-

nous network; only 1�5% of transfected cells showed a normalTable

1(con

tinu

ed)

Family

Mutation–protein

change

DNAchange

Unreported

orknow

nFamilialor

spon

taneou

sPlantarpain

Palm

oplantar

keratoderm

aThickened

nails

Oral

leucokeratosis

Cystsand/

or

follicular

hyperkeratosis

Born

with

teeth?

80K17

p.Arg94

Cys

c.28

0C>T

Kno

wn

Familial

Not

painful

NA

1toenail

No

Steatocystom

aYes

81K17

p.Leu9

5Pro

c.28

4T>C

Kno

wn

Spon

taneou

sNA;un

der2yearsold

NA;un

der

2yearsold

All20

No

NA

Yes

82K17

p.Leu9

5Pro

c.28

4T>C

Kno

wn

Familial

Verypainful,bu

tdo

esno

tusemedication

PKAll20

No

Pilosebaceou

sYes

83K17

p.Leu9

9Pro

c.29

6T>C

Kno

wn

Familial

Somew

hatpainful

PPK

All20

Yes

Follicular

hyperkeratosis

No

84K17

p.Leu9

9Pro

c.29

6T>C

Kno

wn

Spon

taneou

sVerypainful,bu

tdo

esno

tusemedication

PPK

All20

No

Steatocystom

a,pilosebaceou

s,

follicular

hyperkeratosis

Yes

PK,plantarkeratoderm

a;PPK,palm

oplantar

keratoderm

a;NA,no

tapplicable;ND,no

tdeterm

ined

(protein

consequences

ofasplicesite

mutationno

tknow

nwithcertainty).




filament network (Fig. S1). These results demonstrate that the

mutation p.Arg418Pro is disruptive to the normal filament

network formation, which, in vivo, would result in PC, whereas

p.Arg418Cys, in vitro, produces a normal filament network

similar to wild-type K16 and is therefore unlikely to be patho-

genic.

Another novel mutation identified in K16 is a 6-bp in-

frame deletion mutation, K16 p.Arg418_Arg419del, in family

66, which results in the deletion of two amino acids from the

helix termination motif.

Mutations in KRT17 (PC-K17)

KRT17 mutations were found in 18 families and included four

novel mutations. The most common known mutation found

was K17 p.Asn92Ser; including previous publications (www.

interfil.org) and this study, it occurs in ~8% of PC families

with a confirmed mutation.

Three previously unreported missense mutations were iden-

tified in KRT17. Family 78 was found to harbour a mutation

in K17, p.Arg94Ser. p.Arg94 is a residue already known to be

susceptible to mutation owing to several reported cases result-

ing in amino acid substitutions p.Arg94Cys, p.Arg94His and

p.Arg94Pro (www.interfil.org). Two other unreported muta-

tions in K17 were p.Met88Arg (family 68) (mutations have

been previously found at this residue p.M88, p.Met88Lys and

p.Met88Thr) and p.Leu91Pro (family 70). A novel insertion/

deletion mutation in K17, p.Asn90_Asp93delinsIle, found in

Family 69, results in deletion of 10 nucleotides and insertion

of one nucleotide (T). This leads to an in-frame deletion in a

critical region within the helix initiation motif.

Discussion

The mutations identified in these 84 families add to the increas-

ing data set of the IPCRR of detailed clinical information and

corresponding molecular data of individuals with PC. In all

cases, the mutations were heterozygous sequence changes –

missense, nonsense, small deletion/insertion or splice-site

mutations – confirming this is predominantly, if not exclusively,

an autosomal dominant disorder. While there are a few case

reports of recessive PC reported in the literature,19 as yet there

are no recessive cases with confirmed genetic testing.

The majority of the mutations identified have been previously

reported with some mutations, for example K6a p.Asn172del,

K16 p.Asn125Ser, K16 p.Arg127Cys and K17 p.Asn92Ser occur-

ring frequently. For development of mutation-specific forms of

treatment, for example small interfering RNA, these residues

that are commonly mutated would be obvious targets owing to

the larger number of patients that could potentially be treated.

(a)

(b)

Fig 2. Kyle–Doolittle hydrophilicity analysis of normal and mutant K6a. (a) Normal K6a tail domain consists of alternating hydrophobic and

hydrophilic sequences compared with (b) the mutant tail domain, K6a p.Glu473GlyfsTer91, which is mainly hydrophilic.




More than a third of cases analysed in this study had mutations

in K6a, which may partly be reflected by the fact that individuals

with K6a mutations tend to present with the most severe fea-

tures of PC and are therefore more likely to search/ask for sup-

port, find the PC Project website (www.pachyonychia.org) and

join the IPCRR. Conversely, only two families were identified

with mutations in KRT6C. In family 42, the proband had for

many years been diagnosed with EBS due to blistering of palms

and soles and subsequent hyperkeratosis. From the four cases

previously reported with KRT6C mutations,17 together with

those in this report, it appears that these individuals present

with a milder clinical phenotype than those with mutations in

KRT6A, KRT6B, KRT16 or KRT17. Information regarding the phe-

notype of those with mutations in KRT6C is limited due to the

small number of reported cases but this could be explained as

only rarely do they come to clinical attention.

The results reported here, together with previously pub-

lished data, are summarized in Figure 3, which shows the

spectrum of mutations in the five keratin genes associated

with PC: KRT6A, KRT6B, KRT6C, KRT16 and KRT17.

The overlapping phenotype of inherited PPKs, independent

of their genotype, can make diagnosing them clinically a con-

fusing field.

Individuals presenting with symptoms of PC should

undergo genetic analysis for mutations in the five known PC

genes (KRT6A, KRT6B and KRT6C, KRT16 and KRT17). In addi-

tion, other candidate genes may need to be considered,

including GJB6 encoding connexin 30,20 desmoglein 1

(DSG1),21 desmoplakin (DSP),22 keratin 9 (KRT9),17 and friz-

zled 6,23,24 mutations in that mimic some features of the PC

phenotype and hence should be encompassed into the

differential diagnosis of PC. For example, individuals with

mutations in connexin, 30 present with nail dystrophy, some

PPK and alopecia. The severity of the alopecia varies widely

from very subtle to total alopecia but is a key indicator of

Clouston syndrome due to mutations in connexin 30, rather

than a diagnosis of PC. Autosomal dominant mutations in

DSG121 and DSP, typically result in striate PPK,25 although this

can also occur in some patients with PC.

Autosomal recessive cases due to desmoplakin mutations

also have features that overlap with PC, including palmoplan-

tar blistering and keratoderma with nail dystrophy, which can

lead to misdiagnosis. However, these individuals also have dis-

tinctive sparse, woolly hair and, importantly, they are at risk

of cardiomyopathy. Therefore, diagnosis at the molecular level

is important for these individuals in defining the risk of car-

diomyopathy and to allow appropriate monitoring of their

condition.

Mutations in FZD6 were recently discovered as the cause of

autosomal recessive nail dysplasia.23 These individuals present

with 20-nail dystrophy from birth or shortly afterwards in the

form of thickened, discoloured, claw-shaped nails. There is no

involvement of other ectodermal tissues. FZD6 screening

should be considered for any spontaneous cases or known

recessive cases with isolated nail dystrophy.

Genetic analysis of the cases in this study has confirmed

their clinical diagnosis of PC. A small number of cases within

the IPCRR (not reported here) that are clinically not typical of

PC have been shown to have mutations in the other genes

mentioned above. Correct molecular diagnosis is important to

aid in appropriate genetic counselling and patient care. This

large, well-phenotyped and genotyped case series is an invalu-

able resource for the development of mutation-specific and/or

gene-specific therapies, and for future clinical trials.

Acknowledgments

We thank all the patients and families involved in this study.

We also thank all the referring physicians: Dr Susan J. Bayliss,

Washington University School of Medicine, St Louis, MO,

U.S.A.; Dr Jeffrey F. Corpuz, University of Santo Tomas Hospi-

tal, Manila, Philippines; Dr Inacio Rezende Faver, IR Faver

Clinic, Miracema-RJ, Brazil; Dr Celia Posada Garcia, Hospital

Provincial Dermatology Service, Pontevedra, Spain; Dr Ros-

amaria Gomes, Macei, Alagoas, Brazil; Dr Alan Irvine, Our

Lady’s Hospital for Sick Children, Dublin, Ireland; Dr Vanesa

L�opez Gonz�alez, Unidad de Gen�etica M�edica, Murcia, Spain;

Dr K. Kempcke, Universit€ats-Hautklinik Kiel, Kiel, Germany;

Dr Rudolph Leube, Institute of Molecular and Cellular Anat-

omy, Germany; Dr Helen Lewis, Queen Elizabeth Hospital,

Birmingham, U.K.; Dr Jemima E. Mellerio, Guy’s & St. Tho-

mas’ Hospital, London, U.K.; Dr Elena Montalvan Miro, Uni-

versity of Puerto Rico School of Medicine, San Juan, Puerto

Rico; Dr Megan Mowbray, Queen Margaret Hospital, Dun-

fermline, U.K.; Dr Anders Vahlquist, Uppsala University Hos-

pital, Sweden; Dr Theresa A. Scholz, Accent Dermatology and

Laser Institute, Lakewood, CO, U.S.A.; Dr Yasushi Suga,

Juntendo University, Chiba, Japan; and Dr Wujanto, Luton

KRT6A 44%

KRT6B 5%

KRT6C2%

KRT16 25%

KRT17 24%

Fig 3. Spectrum of mutations causing pachyonychia congenital (PC),

showing the percentage of families in this study and previous

publications with mutations in the five keratin genes associated with

PC: KRT6A, KRT6B, KRT6C, KRT16 and KRT17.




Hospital, U.K. Thanks also to Holly Evans of PC Project for all

her help with data preparation.

References

1 Jadassohn J, Lewandowski F. [Pachyonychia Congenita: Keratosis Dissemi-

nata Circumscripta (Follicularis). Tylomata. Leukokeratosis Linguae.] Berlin:Urban and Schwarzenberg, 1906.

2 Munro CS, Carter S, Bryce S et al. A gene for pachyonychia con-genita is closely linked to the keratin gene cluster on 17q12–q21.

J Med Genet 1994; 31:675–8.3 Lane EB, Rugg EL, Navsaria H et al. A mutation in the conserved

helix termination peptide of keratin 5 in hereditary skin blistering.Nature 1992; 356:244–6.

4 Vassar R, Coulombe PA, Degenstein L et al. Mutant keratin expres-sion in transgenic mice causes marked abnormalities resembling a

human genetic skin disease. Cell 1991; 64:365–80.5 Bonifas JM, Rothman AL, Epstein EH. Epidermolysis bullosa sim-

plex: evidence in two families for keratin gene abnormalities.Science 1991; 254:1202–5.

6 Bowden PE, Haley JL, Kansky A et al. Mutation of a type II keratingene (K6a) in pachyonychia congenita. Nat Genet 1995; 10:363–5.

7 McLean WHI, Rugg EL, Lunny DP et al. Keratin 16 and keratin 17mutations cause pachyonychia congenita. Nat Genet 1995; 9:273–8.

8 Smith FJD, Jonkman MF, van Goor H et al. A mutation in human

keratin K6b produces a phenocopy of the K17 disorder pachyony-chia congenita type 2. Hum Mol Genet 1998; 7:1143–8.

9 Wilson NJ, Messenger AG, Leachman SA et al. Keratin K6c muta-tions cause focal palmoplantar keratoderma. J Invest Dermatol 2010;

130:425–9.10 McLean WH, Hansen CD, Eliason MJ et al. The phenotypic and

molecular genetic features of pachyonychia congenita. J InvestDermatol 2011; 131:1015–7.

11 Moll R, Divo M, Langbein L. The human keratins: biology andpathology. Histochem Cell Biol 2008; 129:705–33.

12 Schweizer J, Bowden PE, Coulombe PA et al. New consensusnomenclature for mammalian keratins. J Cell Biol 2006; 174:169–

74.13 Steinert PM, Parry DA. Intermediate filaments: conformity and

diversity of expression and structure. Annu Rev Cell Biol 1985; 1:41–65.

14 Steinert PM, Yang JM, Bale SJ, Compton JG. Concurrence betweenthe molecular overlap regions in keratin intermediate filaments

and the locations of keratin mutations in genodermatoses. BiochemBiophys Res Commun 1993; 197:840–8.

15 Smith FJ, Liao H, Cassidy AJ et al. The genetic basis of pachyony-chia congenita. J Investig Dermatol Symp Proc 2005; 10:21–30.

16 Wilson NJ, Leachman SA, Hansen CD et al. A large mutationalstudy in pachyonychia congenita. J Invest Dermatol 2011; 131:1018–

24.17 Szeverenyi I, Cassidy AJ, Chung CW et al. The Human Intermediate

Filament Database: comprehensive information on a gene familyinvolved in many human diseases. Hum Mutat 2008; 29:351–60.

18 Fu T, Leachman SA, Wilson NJ et al. Genotype–phenotype correla-tions among pachyonychia congenita patients with K16 mutations.

J Invest Dermatol 2011; 131:1025–8.19 Haber RM, Rose TH. Autosomal recessive pachyonychia congenita.

Arch Dermatol 1986; 122:919–23.20 van Steensel MAM, Jonkman MF, van Geel M et al. Clouston syn-

drome can mimic pachyonychia congenita. J Invest Dermatol 2003;121:1035–8.

21 Rickman L, Imrak D, Stevens HP et al. N-terminal deletion in adesmosomal cadherin causes the autosomal dominant skin disease

striate palmoplantar keratoderma. Hum Mol Genet 1999; 8:971–6.

22 Smith FJ, Wilson NJ, Moss C et al. Compound heterozygous muta-tions in desmoplakin cause skin fragility and woolly hair. Br J

Dermatol 2012; 166:894–6.23 Frojmark AS, Schuster J, Sobol M et al. Mutations in Frizzled 6

cause isolated autosomal-recessive nail dysplasia. Am J Hum Genet2011; 88:852–60.

24 Wilson NJ, Hansen CD, Azkur D et al. Recessive mutations in thegene encoding frizzled 6 cause twenty nail dystrophy – expanding

the differential diagnosis for pachyonychia congenita. J Dermatol Sci2013; 70:58–60.

25 Armstrong DK, McKenna KE, Purkis PE et al. Haploinsufficiency ofdesmoplakin causes a striate subtype of palmoplantar keratoderma.

Hum Mol Genet 1999; 8:143–8.

Supporting Information

Additional Supporting Information may be found in the online

version of this article at the publisher’s website:

Figure S1. Double-label immunofluorescence staining of

cells transiently transfected with K16 wild-type and mutant

K16. (a) K16 wild-type, (b) K16 p.Arg418Cys and (c) K16

p.Arg418Pro cDNAs in epithelial cell line PtK2. K16 was

detected with rabbit polyclonal antisera against human K16

and the endogenous K8 with monoclonal antibody LE41 to

PtK2 K8. Nuclei were stained with 40,6-diamidino-2-phenylin-

dole (DAPI). In cells transfected with wild-type K16, 89�5% of

transfected cells showed a defined keratin cytoskeleton where

wild-type K16 co-localized with endogenous K8; the remain-

ing 10�5% of transfected cells had filaments plus aggregates. In

cells transfected with K16 p.Arg418Cys, similar to wild-type

K16, 89% of transfected cells had a normal filament network

and 11% of cells had filaments plus aggregates. In contrast, in

cells transfected with K16 p.Arg418Pro, 98�5% of cells con-

tained aggregates and there was collapse/aggregation of the

endogenous network; only 1�5% of transfected cells showed a

normal filament network. Original magnification 9 60.

Table S1. Polymerase chain reaction primers for specific

amplification of pachyonychia congenita-associated keratin

genes.




15

PC-K17

N=116

112 of 116 (97%)

87 of 116 (75%)

10 of 116 (09%)

7 of 116 (06%)

8 of 116 (07%)



1 to 4 years old 24 of 112 (21%)

5 to 14 years old 9 of 112 (08%)


98 of 116 (84%)

50 of 116 (43%)

12 of 116 (10%)

27 of 116 (23%)

9 of 116 (08%)



1 to 4 years old 19 of 98 (19%)

5 to 14 years old 5 of 98 (05%)


91 of 116 (78%)

74 of 116 (64%)

13 of 116 (11%)

4 of 116 (03%)



1 to 4 years old 29 of 91 (32%)

5 to 14 years old 37 of 91 (41%)


77 of 91 (85%)

17 of 91 (19%)

28 of 91 (31%)

32 of 91 (35%)

60 of 116 (52%)

16 of 116 (14%)

19 of 116 (16%)

24 of 116 (21%)

29 of 116 (25%)

107 of 116 (92%)

75 of 116 (65%)

88 of 116 (76%)

Oral Leukokeratosis

Cysts



Other




Plantar Pain



Somewhat painful

Palmar Keratoderma




Plantar Keratoderma

K17 N92S Data for IPCRR #515

Toenails Dystrophy










E Grand Rounds Presentation Pachyonychia Congenita€¦ · E Grand Rounds Presentation Pachyonychia...

Documents

Transcript of E Grand Rounds Presentation Pachyonychia Congenita€¦ · E Grand Rounds Presentation Pachyonychia...