ORIGINAL PAPER

Effects of interleukin (IL)-6 gene polymorphisms on recurrentaphthous stomatitis

Nevin Karakus • Serbulent Yigit • Aydin Rustemoglu •

Goknur Kalkan • Nihan Bozkurt

Received: 31 May 2013 / Revised: 6 August 2013 / Accepted: 9 August 2013 / Published online: 28 August 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract Recurrent aphthous stomatitis (RAS) is a

common disease with oral ulceration in which cytokines

are thought to play an important role. High levels of

interleukin (IL)-6, a pro-inflammatory cytokine have been

detected in the circulation of ulcer tissue. The purpose of

the present study was to investigate if the IL-6 gene

polymorphisms are associated with RAS or clinical char-

acteristics of RAS in a cohort of Turkish population. 184

RAS patients and 150 healthy controls were included in the

study. The genotypes of IL-6 gene -572G[C and

-174G[C polymorphisms were determined using poly-

merase chain reaction based restriction fragment length

polymorphism analysis. The genotype frequencies of

-572G[C polymorphism showed statistically significant

differences between RAS patients and controls (p = 0.01).

Frequencies of GG ? GC genotypes and G allele of

-572G[C polymorphism were found higher in RAS

patients (p = 0.0001, OR 10.8, 95 % CI 2.79–70.5;

p = 0.0008, OR 2.06, 95 % CI 1.35–3.17, respectively).

The genotype frequencies of -174G[C polymorphism

also showed statistically significant differences between

RAS patients and controls (p \ 0.0001). Frequencies of

GG genotype and G allele of -174G[C polymorphism

were found higher in RAS patients (p \ 0.0001, OR 4.87,

95 % CI 3.06–7.85; p \ 0.0001, OR 3.82, 95 % CI

2.64–5.59, respectively). GG–GG combined genotype and

G–G haplotype of -174G[C to -572G[C loci were also

significantly higher in RAS patients (p \ 0.0001 and

p = 1.5 9 10-8, respectively). After stratifying clinical

and demographical characteristics of RAS patients

according to IL-6 gene polymorphisms, an association was

observed between family history of RAS and -174G[C

polymorphism (p = 0.011). Susceptibility effects of both

IL-6 gene -572G[C and -174G[C polymorphisms for

RAS were observed. Further studies are necessary to prove

the association of IL-6 gene polymorphisms with RAS.

Keywords Recurrent aphthous stomatitis (RAS) �Interleukin (IL)-6 � Genetic susceptibility � Cytokine �Oral ulceration

Introduction

Recurrent aphthous stomatitis (RAS) is a common disease

with recurrent episodes of oral ulceration [17]. It has been

estimated that approximately 25 % of the general popula-

tion, regardless of age, race and geographic region, might

suffer from RAS at some time in their lives [20]. Family

history of RAS was identified in more than 40 % of RAS

patients [15]. There may be possible factors associated with

RAS such as local trauma, stress, trait anger, anxiety,

drugs, hormonal changes, vitamin and trace element defi-

ciencies, socioeconomics, allergies, mechanical injury and

preservatives [15, 30]. Local and systemic conditions and

genetic, immunological and microbial factors may also

play a role in the pathogenesis of RAS [15].

Immune dysfunction occurs during the ulcerative stage

of RAS [17]. In the earliest stages, focal epithelial cell

degeneration occur [23]. A lympho-monocytic infiltrate

develops adjacent to the damaged cells. It is supposed that

N. Karakus (&) � S. Yigit � A. Rustemoglu � N. Bozkurt

Department of Medical Biology, Faculty of Medicine,

Gaziosmanpasa University, 60100 Tokat, Turkey

e-mail: nevinbalci@hotmail.com

G. Kalkan

Department of Dermatology, Faculty of Medicine,

Gaziosmanpasa University, Tokat, Turkey

123

Arch Dermatol Res (2014) 306:173–180

DOI 10.1007/s00403-013-1406-x

RAS is formed by a local damage in an individual genet-

ically predisposed to an abnormal cytokine cascade.

Although extreme serum levels of interleukin (IL)-6, a pro-

inflammatory cytokine that regulates a wide range of

activities, was not observed in RAS patients [16], high

levels of IL-6 have been detected in the circulation of ulcer

tissue [24, 29]. IL-6 is produced by a variety of cells

including macrophages, B cells, T cells, and fibroblasts and

plays important roles in regulating hematopoiesis, immune

cell activation, and inflammation [11].

IL-6 gene is located on chromosome 7p21 [5]. IL-6

expression is almost regulated at the transcriptional level

by regulatory elements in the promoter region of the gene

[14]. A number of polymorphisms have been detected in

this region of IL-6. The -174G[C and -572G[C poly-

morphisms in the promoter region are important regulators

of transcription [12]. The IL-6 gene -174G[C polymor-

phism is located immediately upstream of a multiresponse

element at positions -173 to -151 [8]. The IL-6

-572G[C polymorphism is located near a potential glu-

cocorticoid receptor element at position -557 to -552 [6].

IL-6 production is modulated by these polymorphisms and

has been associated with susceptibility to many several

pathological conditions [2, 4, 7, 8, 22, 25]. There have been

only a few studies dealing with the relationship between

IL-6 promoter polymorphisms and RAS, and their results

have been conflicting. While Bazrafshani et al. [3] reported

a positive association between carriage of the IL-6 -174

GG genotype and RAS, others could not confirm this

observation [10].

The purpose of the present study was to investigate if the

IL-6 gene -174G[C and -572G[C polymorphisms and

combined genotypes and haplotypes are associated with

RAS or clinical characteristics of RAS in a cohort of

Turkish population.

Materials and methods

Subjects

The study group consisted of 184 unrelated patients with

RAS [66 males and 118 females; mean age 35.96 ± 11.645

standard deviation (SD) years], and 150 (62 male and 88

female; mean age 37.28 ± 13.091 SD years) unrelated

healthy controls. RAS patients were recruited consecu-

tively and prospectively from those whom were treated and

followed up in the Dermatology Department of Gazios-

manpasa University Research Hospital, Tokat, Turkey

between January 2012 and December 2012. The diagnosis

of RAS was performed by a dermatologist according to the

history and physical examination based on accepted clini-

cal criteria [21]. RAS was divided into three clinical

features: major (larger than 1 cm and deeper than minor

RAS and healing within 10–30 days), minor (less than

1 cm in diameter and healing within 4–14 days) and her-

petiform aphthae (grouped aphthae, 1–2 mm in size and

painful). Only patients with major and minor RAS were

included in this study. All RAS patients recruited had at

least three recurrences of oral ulcers per year. None of the

patients suffered from Behcet’s Disease, inflammatory

bowel disease, or any systemic disease, and none received

any systemic treatment that could influence the results of

tests performed in this study. The study groups were also

non-smokers and non-alcohol users. Patients were other-

wise healthy and had active aphthous lesions during the

study. The following routine laboratory tests (complete

blood count, liver enzymes, fasting glucose, ferritine,

vitamin B12 and folic acid) were performed. The patients

with abnormal laboratory findings were excluded. The

control group was comprised of patients with no history of

RAS or systemic diseases, who were admitted to derma-

tology clinic with other reasons; for nevus examination,

treatment of warts, tinea pedis or for contact dermatitis.

Exclusion criteria for controls included the presence of any

other significant local or systemic diseases; Behcet’s dis-

ease, coeliac disease and other gastrointestinal symptoms

and/or diseases. All participants, patients and healthy

controls, were of Turkish origin, from the inner Central

Black Sea region of Turkey. The healthy controls were

matched for age and gender with RAS patients (Table 1).

The study protocol was approved by the Local Ethics

Committee of Gaziosmanpasa University, Faculty of

Medicine and written informed consent was obtained from

the study participants or from the parents when subjects

were \18 years.

Genotyping

Genomic DNA was extracted from whole venous blood

samples using a commercial DNA isolation kit (Sigma-

Aldrich, Taufkirchen, Germany). The IL-6 gene -572G[C

(rs1800796) and -174G[C (rs1800795) polymorphisms

Table 1 The demographical characteristics of patients with RAS and

healthy controls

RAS patients

n = 184

Healthy controls

n = 150

p value

Gender 0.311

Female 118 (64.1) 88 (58.7)

Male 66 (35.9) 62 (41.3)

Age (years) 35.98 ± 11.871 37.28 ± 13.091 0.344

Data were analyzed by analysis of variance and v2 test. Mean plus

standard deviation values are presented for age

174 Arch Dermatol Res (2014) 306:173–180

123

were analyzed by polymerase chain reaction (PCR) based

restriction fragment length polymorphism (RFLP) analysis.

The PCR amplifications were carried out in a total volume

of 25 ll reaction containing 100 ng of genomic DNA,

2.5 ll of 109 PCR buffer, 200 lM dNTP, 10 pM each

primers, and one unit of Taq DNA polymerase. The IL-6

-174G[C polymorphism was analyzed as previously

described by Tseng et al. [27] using forward (f) 50-TTG

TCA AGA CAT GCC AAA GTG CGG AG-30 and reverse

(r) 50-GTG CAA TGT GAC GTC CCT TAG CAT-30

primers. The amplification conditions consisted of an initial

melting step of 5 min at 94 �C; followed by 40 cycles of

30 s at 94 �C, 30 s at 56 �C and 1 min at 72 �C. After

amplification, the 156 bp PCR product was digested with

FastDigest BseL-I restriction endonuclease (Fermentas) at

37 �C for 30 min and analyzed on a 3 % agarose gel

stained with ethidium bromide. Two fragments (139 and

17 bp) for G allele and three fragments (117, 22 and 17 bp)

for C allele were observed. For IL-6 -572G[C polymor-

phism, the sequences of PCR primers were (f) 50-CAG

CAG CCA ACC TCC TCT AA-30 and (r) 50-CCA AGC

CTG GGA TTA TGA AG-30. The cycling conditions for

-572G[C polymorphism were 40 cycles of 30 s at 95 �C,

30 s at 62 �C and 1 min at 72 �C. 224 bp PCR product was

digested with FastDigest BsrB-I restriction endonuclease

(Fermentas) at 37 �C for 30 min and analyzed on a 3 %

agarose gel stained with ethidium bromide. While two

fragments (150 and 74 bp) were observed for G allele, only

one fragment (224 bp) was observed for C allele. Second

PCR was performed to confirm samples whose results were

not clear.

Statistical analysis

Statistical analysis was performed using the Statistical

Package for the Social Sciences (SPSS 20), Arlequin

software version 3.1.1 and OpenEpi Info software

package version 3.01 (www.openepi.com). Results were

given as mean ± standard deviation. Allelic frequencies,

haplotypes, haplotype frequencies, Hardy–Weinberg

equilibrium (HWE), LD between SNP pairs were per-

formed by Arlequin software. The relationships between

-174G[C and -572G[C polymorphisms and the clin-

ical and demographical characteristics of patients and

clinical characteristics of oral ulcers of patients were

analyzed by using v2 test or analysis of variance

(ANOVA) statistics. v2 test and Fisher’s exact test were

used to compare categorical variables appropriately,

and odds ratio (OR) and 95 % confidence interval (CI)

were used for the assessment of risk factors. All p values

were two-tailed and p values \0.05 were considered as

significant.

Results

The baseline clinical and demographical characteristics

of RAS patients are presented in Table 2. Gender, age,

age at disease onset, family history, papulopustule,

systemic involvement and colchicine use of RAS

patients were analyzed. No patient was found with

erythema nodosum, genital ulcers and pathergy positiv-

ity. Although no association was not found between

clinical and demographical characteristics of RAS

patients and IL-6 gene -572G[C polymorphism, an

association was observed between family history of RAS

and IL-6 gene -174G[C polymorphism (p = 0.011)

(Table 2). The frequency of CC genotype was higher in

RAS patients with no family history of RAS (1.4 %)

than the patients with family history of RAS (5.3 %).

Table 3 shows the clinical characteristics (size, number,

frequency and period of recovery) of oral ulcers of RAS

patients. There was no statistically significant associa-

tion between characteristics of oral ulcers of RAS

patients and IL-6 gene -572G[C and -174G[C

polymorphisms.

Allelic and genotypic distributions of IL-6 gene

-572G[C and -174G[C polymorphisms are shown in

Table 4. The frequencies of GG, GC and CC genotypes of

-572G[C polymorphism in the patients were 78.3, 20.7,

and 1.1 % and in the controls were 68.7, 20.7, and 10.7 %.

Genotype frequencies of IL-6 gene -572G[C polymor-

phism were significantly different between patients and

controls (p = 0.001) due to an increased frequency of G

allele in patient group (p = 0.0008, OR 2.06, 95 % CI

1.35–3.17). This was reflected in the significantly increased

number of GG homozygotes and GC heterozygotes

(p = 0.0001, OR 10.8, 95 % CI 2.79–70.5) among

patients.

The frequencies of GG, GC and CC genotypes of IL-6

gene -174G[C polymorphism in the patients were 75.5,

20.7, and 3.8 % and in the controls were 38.7, 45.3, and

16.0 %. Genotype frequencies of IL-6 gene -174G[C

polymorphism were significantly different between patients

and controls (p \ 0.0001) due to an increased frequency of

G allele in patient group (p \ 0.0001, OR 3.82, 95 % CI

2.64–5.59) (Table 4). This was reflected in the significantly

increased number of GG homozygotes (p \ 0.0001, OR

4.87, 95 % CI 3.06–7.85) among patients.

As IL-6 gene -572G[C and -174G[C polymorphisms

were both associated with RAS, the risk associated

with inheriting the combined genotypes was examined

(Table 5). Homozygosity for GG at -174G[C and

-572G[C loci encoded a p value of\0.0001. Thus, indi-

viduals who are G homozygous at both loci have a higher risk

of developing RAS. However GG–CC, GC–GG, GC–GC

Arch Dermatol Res (2014) 306:173–180 175

123

Ta

ble

2C

lin

ical

and

dem

og

rap

hic

alch

arac

teri

stic

so

fR

AS

pat

ien

tsst

rati

fied

acco

rdin

gto

IL-6

gen

e-

57

2G[

Can

d-

17

4G[

Cp

oly

mo

rph

ism

s

Ch

arac

teri

stic

sT

ota

ln

=1

84

-5

72

G[

Cp

oly

mo

rph

ism

-1

74

G[

Cp

oly

mo

rph

ism

GG

n=

14

4G

Cn

=3

8C

Cn

=2

pv

alu

eG

Gn

=1

39

GC

n=

38

CC

n=

7p

val

ue

Gen

der

,m

ale/

fem

ale,

n(%

)6

6/1

18

(35

.9/6

4.1

)4

9/9

5(7

4.2

/80

.5)

16

/22

(24

.2/1

8.6

)1

/1(1

.5/0

.8)

0.5

98

54

/85

(81

.8/7

2.0

)1

0/2

8(1

5.2

/23

.7)

2/5

(3.0

/4.2

)0

.33

2

Ag

e(y

ears

)3

5.9

8±

11

.87

13

6.4

2±

12

.02

33

4.6

1±

10

.97

53

0.5

0±

13

.43

50

.56

93

6.5

3±

11

.70

73

5.2

9±

12

.45

52

9.0

0±

11

.04

50

.24

3

Ag

eat

dis

ease

on

set

(yea

rs)

28

.55

±1

1.5

94

29

.05

±1

2.0

23

26

.89

±9

.57

12

4.5

0±

19

.09

20

.52

92

8.7

1±

11

.29

32

8.4

7±

13

.05

02

6.0

0±

10

.39

20

.83

5

Fam

ily

his

tory

of

RA

S,

n(%

)0

.17

40

.01

1

Yes

70

(38

.0)

55

(78

.6)

13

(18

.6)

2(2

.9)

47

(67

.1)

22

(31

.4)

1(1

.4)

No

11

4(6

2.0

)8

9(7

8.1

)2

5(2

1.9

)0

92

(80

.7)

16

(14

.0)

6(5

.3)

Pap

ulo

pu

stu

le,

n(%

)0

.89

00

.93

7

Yes

19

(10

.3)

15

(78

.9)

4(2

1.1

)0

14

(73

.7)

4(2

1.1

)1

(5.3

)

No

16

5(8

9.7

)1

29

(78

.2)

34

(20

.6)

2(1

.2)

12

5(7

5.8

)3

4(2

0.6

)6

(3.6

)

Sy

stem

icin

vo

lvem

ent,

n(%

)0

.87

00

.14

5

Yes

1(0

.5)

1(1

00

)0

00

1(1

00

)0

No

18

3(9

9.5

)1

43

(78

.1)

38

(20

.8)

2(1

.1)

13

9(7

6.0

)3

7(2

0.2

)7

(3.8

)

Co

lch

icin

eu

se,

n(%

)0

.81

00

.58

5

Yes

24

(14

.6)

18

(75

.0)

6(2

5.0

)0

19

(79

.2)

5(2

0.8

)0

No

14

0(8

5.4

)1

07

(76

.4)

31

(22

.1)

2(1

.4)

10

7(7

6.4

)2

7(1

9.3

)6

(4.3

)

Ery

them

an

od

osu

m–

––

––

––

––

Gen

ital

ulc

ers

––

––

––

––

–

Pat

her

gy

po

siti

vit

y–

––

––

––

––

Dat

aw

ere

anal

yze

db

yan

aly

sis

of

var

ian

cean

dv2

test

.M

ean

plu

sst

and

ard

dev

iati

on

val

ues

are

pre

sen

ted

for

age

and

age

atd

isea

seo

nse

t

Th

ere

sult

sth

atar

est

atis

tica

lly

sig

nifi

can

tar

esh

ow

nin

bo

ldfa

ce

IL-6

inte

rleu

kin

6,

RA

Sre

curr

ent

aph

tho

us

sto

mat

itis

176 Arch Dermatol Res (2014) 306:173–180

123

and CC–GG combined genotypes of -174G[C to

-572G[C loci were significantly higher in control group

than patient group that these combined genotypes seem to

have protective effect against RAS (p = 0.029, p = 0.004,

p = 0.005, p = 0.0008, respectively). The haplotype

characteristics of RAS patients and controls are given in

Table 6. The G–G haplotype was observed to be signifi-

cantly higher in the patient group (74.46 vs 45.40 %,

p = 1.5 9 10-8), and the two others, C–G (14.13 vs

33.60 %, p = 7.5 9 10-9) and C–C (0 vs 5.07 %,

p = 5.0 9 10-6) were found to be significantly higher in

control subjects (Table 6). The linkage disequilibrium

(LD) between pairs of IL-6 gene polymorphisms in the

RAS patients and the control group are tabulated in

Table 6. No linkage in FMF patients and controls was

detected between -174G[C and -572G[C loci. The

observed and expected frequencies of IL-6 gene -572G[C

polymorphism were in Hardy–Weinberg equilibrium in

patient group but not in control group. However, the

observed and expected frequencies of IL-6 gene -174G[C

polymorphism were in Hardy–Weinberg equilibrium in

both groups.

Discussion

In the present study, a highly significant differences were

detected, between patients with RAS and control subjects,

in the genotype and allele frequencies of -572G[C and

-174G[C polymorphisms located in the promoter region

IL-6 gene. Patients with RAS had a lower frequency of the

minor alleles (C allele, low producer allele) for both the

polymorphisms. These results suggested that having a high

producer phenotype for carriage of IL-6 gene promoter

polymorphisms may cause oral ulcer formation, in accor-

dance to what has been demonstrated by Bazrafshani et al.

[3] who analyzed the -174G[C and -572G[C poly-

morphisms in an American Caucasian population. In this

previous study, a significant difference in the distribution

of IL-6 gene -174G[C polymorphism was observed in 91

Caucasoid RAS patients and 91 controls (p = 0.0002) [3].

In this study, the G allele observed is significantly higher in

RAS patients (p = 0.0001) and greatest risk of RAS was

associated with GG homozygosity (OR = 3.4; 95 % CI

1.9–6.2; p = 0.0001). However, in the same study, differ-

ently from our results, no significant association was

Table 3 Clinical characteristics of oral ulcers of RAS patients stratified according to IL-6 gene -572G[C and -174G[C polymorphisms

Characteristics Total

n = 184

-572G[C polymorphism -174G[C polymorphism

GG

n = 144

GC

n = 38

CC

n = 2

p value GG

n = 139

GC

n = 38

CC

n = 7

p value

Size, n (%) 0.659 0.211

Minor (MiRAS) 105 (57.1) 79 (75.2) 24 (22.9) 2 (1.9) 82 (78.1) 19 (18.1) 4 (3.8)

Major (MaRAS) 26 (14.1) 21 (80.8) 5 (19.2) 0 21 (80.8) 3 (11.5) 2 (7.7)

Minor ? major 53 (28.8) 44 (83.0) 9 (17.0) 0 36 (67.9) 16 (30.2) 1 (1.9)

Number, n (%) 0.327 0.106

One 56 (30.4) 43 (76.8) 11 (19.6) 2 (3.6) 47 (83.9) 9 (16.1) 0

Two 83 (45.1) 64 (77.1) 19 (22.9) 0 57 (68.7) 23 (27.7) 3 (3.6)

Three 27 (14.7) 24 (88.9) 3 (11.1) 0 21 (77.8) 4 (14.8) 2 (7.4)

CFour 18 (9.8) 13 (72.2) 5 (27.8) 0 14 (77.8) 2 (11.1) 2 (11.1)

Frequency, n (%) 0.208 0.519

Once a month 50 (27.2) 36 (72.0) 12 (24.0) 2 (4.0) 39 (78.0) 8 (16.0) 3 (6.0)

Twice a month 31 (16.8) 22 (71.0) 9 (29.0) 0 26 (83.9) 5 (16.1) 0

Three times a month 18 (9.8) 16 (88.9) 2 (11.1) 0 13 (72.2) 5 (27.8) 0

Four times a month 49 (26.6) 37 (75.5) 12 (24.5) 0 35 (71.4) 11 (22.4) 3 (6.1)

Once in 2 months 20 (10.9) 17 (85.0) 3 (15.0) 0 12 (60.0) 7 (35.0) 1 (5.0)

Once in 3 months 16 (8.7) 16 (100) 0 0 14 (87.5) 2 (12.5) 0

Period of recovery, n (%) 0.453 0.970

1 week 95 (51.6) 76 (80.0) 17 (17.9) 2 (2.1) 71 (74.7) 19 (20.0) 5 (5.3)

2 weeks 81 (44.0) 62 (76.5) 19 (23.5) 0 62 (76.5) 17 (21.0) 2 (2.5)

3 weeks 4 (2.2) 4 (100) 0 0 3 (75.0) 1 (25.0) 0

[3 weeks 4 (2.2) 2 (50.0) 2 (50.0) 0 3 (75.0) 1 (25.0) 0

Data were analyzed by v2 test

RAS recurrent aphthous stomatitis, IL-6 interleukin 6

Arch Dermatol Res (2014) 306:173–180 177

123

observed with IL-6 gene -572G[C polymorphism and

RAS. Another previous study composed of 64 RAS

patients and 64 controls, Guimaraes et al. [10] did not

found any difference in allele and genotype frequencies of

the -174G[C polymorphism in a Brazilian cohort with

RAS in comparison to controls.

According to combined genotypes and haplotype anal-

ysis, GG–GG combined genotype and G–G haplotype of

-174G[C to -572G[C loci were found significantly

higher in RAS patients (p \ 0.0001 and p = 1.5 9 10-8,

respectively) in our study and these combined genotype

and haplotype represented by the G allele for the -597 and

-174 loci appear to favor a progressive disease. IL-6 gene

-572G[C polymorphism was not found to be in linkage

disequilibrium with the -174G[C polymorphism [7] as we

confirmed in our study. However, the IL-6 gene -174G[C

and -572G[C polymorphisms are very close that an

association with one might be expected to result in asso-

ciation with the other [26, 28].

In vivo and in vitro studies showed that IL-6 gene

-174G[C and -572G[C polymorphisms were associated

with IL-6 production or protein expression [8, 26]. It was

demonstrated that the -174 GG and -174 GC genotypes

characterized by higher circulating IL-6 levels than the

-174 CC genotype accounted for the low producer phe-

notype [8]. A complex interactive effect on IL-6 expression

might exist for the two polymorphisms. High production of

IL-6 could be an important etiological factor for RAS and

could explain the elevated IL-6 plasma levels reported in

RAS [29]. It is important that corticosteroids and thalido-

mide, two of the most effective therapeutic agents in RAS,

are inhibitors of IL-6 production [1, 19].

Genetic factors play an important role in the develop-

ment of RAS. 24–46 % of RAS patients have a positive

family history of RAS [18]. There was also a significantly

Table 4 Genotype and allele frequencies of IL-6 gene -572G[C and -174G[C polymorphisms in patient and control groups

Polymorphism RAS patients n = 184 (%) Healthy controls n = 150 (%) p OR (95 % CI)

IL-6 (-572G[C)

Genotypes

GG 144 (78.3) 103 (68.7) 0.001

GC 38 (20.7) 31 (20.7)

CC 2 (1.1) 16 (10.7)

GG : GC ? CC 144 (78.3) : 40 (21.7) 103 (68.7) : 47 (31.3) 0.049 1.64 (1.00–2.69)

GG ? GC : CC 182 (98.9) : 2 (1.1) 134 (89.3) : 16 (10.7) 0.0001 10.8 (2.79–70.5)

Alleles

G 326 (88.6) 237 (79.0) 0.0008 2.06 (1.35–3.17)

C 42 (11.4) 63 (21.0)

IL-6 (-174G[C)

Genotypes

GG 139 (75.5) 58 (38.7) <0.0001

GC 38 (20.7) 68 (45.3)

CC 7 (3.8) 24 (16.0)

GG : GC ? CC 139 (75.5) : 45 (24.5) 58 (38.7) : 92 (61.3) <0.0001 4.87 (3.06–7.85)

GG ? GC : CC 177 (96.2) : 7 (3.8) 126 (84.0) : 24 (16.0) 0.0001 4.79 (2.06–12.3)

Alleles

G 316 (85.9) 184 (61.3) <0.0001 3.82 (2.64–5.59)

C 52 (14.1) 116 (38.7)

The results that are statistically significant are shown in boldface

Table 5 Comparative analysis of combined genotypes of RAS

patients and controls

Genotypes Patient (n = 184) Control (n = 150) p

n % n %

-174G[C to -572G[C

GG–GG 103 56.0 34 22.7 <0.0001

GG–GC 34 18.5 16 10.7 0.046

GG–CC 2 1.1 8 5.3 0.029

GC–GG 34 18.5 48 32.0 0.004

GC–GC 4 2.2 14 9.3 0.005

GC–CC 0 0 6 4.0 –

CC–GG 7 3.8 21 14.0 0.0008

CC–GC 0 0 1 0.7 –

CC–CC 0 0 2 1.3 –

The results that are statistically significant are typed in bold

RAS recurrent aphthous stomatitis

178 Arch Dermatol Res (2014) 306:173–180

123

higher disease concordance in monozygotic than dizygotic

twins [13]. This can explain the association between family

history of RAS and -174G[C polymorphism that we

detected in our study.

According to our results, the carriage of the low

producer phenotype of the IL-6 gene -174G[C and

-572G[C polymorphisms appears to protect from RAS.

Cytokines play a fundamental role in the immune response

and may to lead to a protective immunity or the tissue

destruction by the production of different profiles of

cytokines [9]. This may explain why lower producer

genotypes appear to protect from RAS.

In conclusion, our findings demonstrated that IL-6 gene

-174G[C and -572G[C promoter polymorphisms influ-

ence formation and course of RAS. If these results can be

substantiated with further studies in different populations,

evaluation for IL-6 gene -174G[C and -572G[C pro-

moter polymorphisms may become necessary in selected

patients.

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