Genetic Factors in Nickel Allergy
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See related article on page 1025 Genetic Factors in Nickel Allergy Veronique Bataille Genetic Epidemiology and Twin Research Unit, St Thomas Hospital, London, UK Atopic disorders represent common and debilitating dis- eases, with a rising incidence over the last 30 y. Almost 30% of the population is affected by a form of atopic disorder. Many study designs have attempted to elucidate the role of genetic and environmental factors in the causation of atopy (Cookson and Moffat, 1999). This task is not simple, as the pathogenesis of atopy is complex, with the likelihood of gene–environment interactions. The relative contribution of genes and environment in the pathogenesis of atopy is not known, but numerous studies have shown that atopy clus- ters in families. It is likely that many different genes are responsible for an individual’s predisposition to allergy and that exposure to certain known and unknown allergens leads to the expression of asthma, eczema, or hay fever. Twin studies have also been useful in estimating the relative importance of genes and environment on atopy, including eczema (Schultz Larsen, 1993; Lichtentstein and Svarteng- ren, 1997; Strachan et al, 2000). Studies based on more than 3000 UK female twins have shown heritability esti- mates for eczema of 60%, with models being in favor of a combination of additive genes and unique environment (Mi- kkilineni et al, 2001). Candidate gene approaches for puta- tive atopy genes have already been conducted by many groups in diverse populations, mainly using the family de- sign (Ono, 2000). Many genes appear to have modest ef- fects on the risk of atopy, and using genome-wide scans many chromosomal regions have been linked to the risk of atopy. The study published in this issue by Brydl et al assesses the relative effects of genes and environment on the nickel allergy in a large population-based sample of female twins. Nickel allergy is a very common disorder affecting 30% of the population with a rising incidence, especially in females who have previously had skin piercing. The potential asso- ciation between nickel allergy and atopy is controversial, as some studies have shown that nickel allergy is more prev- alent in some atopic patients, whereas others have shown no association. Positive prick tests and IgE levels have not been shown to be associated with nickel allergy. Allergic contact dermatitis is dependent on cell-mediated immune response mediated mainly by type 1 lymphocytes, whereas atopic dermatitis is the result of sustained activation of type 2 lymphocytes, but little is known about the true relationship between nickel allergy and atopy. Another potential link be- tween atopy and nickel allergy is the altered barrier function in patients who have atopic hand dermatitis, which may allow greater risk of contact allergy and therefore perpet- uate the hand dermatitis. The twins in the study reported here were first recruited on the basis of having ‘‘hand ec- zema’’. Clinical symptoms of hand dermatitis may be the manifestation of allergic contact dermatitis, irritant con- tact dermatitis, and atopic eczema—which may include dishydrotic eczema—thus the background phenotype of inclusion in this study may be very heterogeneous. The authors conclude that nickel allergy is unlikely to have a genetic basis because of the lack of a greater correlation in identical pairs compared with non-identical pairs. Twin studies are ideally suited to dissecting genetic and environmental influence on a disease or trait, as opposed to family studies that are confused by common environmental influences that cannot clearly be separated from shared genes. But the estimates yielded by twin studies, however, are only applicable to the population studied and the meth- od of ascertaining the twin pairs will also have a significant influence on the results. The study presented here by Brydl et al recruited highly selected twin pairs on the basis of one of the twins having had a history suggestive of ‘‘hand ec- zema’’. Six hundred and thirty female twins who fulfilled the criteria for inclusion were selected from the Danish Twin Registry. On a background of ‘‘hand eczema’’, the authors assessed the potential genetic influence on nickel allergy by patch testing. Although it is possible that nickel allergy is mostly influenced by environmental factors, the fact that the twins were recruited on the basis of a variable phenotype of hand eczema may have affected the results and interpre- tation. The sample size in each age group is also small and the power to discriminate genetic and environmental effects may also be an issue. This study has concluded that given a genetic susceptibility to atopy, there is no major additional genetic component to nickel allergy. Although it is evident that environmental factors such as ear piercing are impor- tant, as the prevalence of nickel allergy is much lower in men, the fact that only a proportion of the female population develops allergy to nickel suggests that genetic factors may also play a role. Studies have also shown some familial clustering in nickel allergy, supporting a genetic basis (Fle- ming et al, 1999). If the specific question about the true role of genes and environment in nickel allergy needs validation, the study should be repeated in an unselected random twin population of sufficient size. DOI: 10.1111/j.0022-202X.2004.23508.x References Brydl LE, Hindsberger C, Kyvik KO, Agner T, Menne T: Genetic factors in nickel allergy evaluated in a population-based female twin sample. J Invest Dermatol 123:1025–1029, 2004 Copyright r 2004 by The Society for Investigative Dermatology, Inc. xxiv
Transcript of Genetic Factors in Nickel Allergy
See related article on page 1025
Genetic Factors in Nickel Allergy
Veronique BatailleGenetic Epidemiology and Twin Research Unit, St Thomas Hospital, London, UK
Atopic disorders represent common and debilitating dis-eases, with a rising incidence over the last 30 y. Almost 30%of the population is affected by a form of atopic disorder.Many study designs have attempted to elucidate the role ofgenetic and environmental factors in the causation of atopy(Cookson and Moffat, 1999). This task is not simple, as thepathogenesis of atopy is complex, with the likelihood ofgene–environment interactions. The relative contribution ofgenes and environment in the pathogenesis of atopy is notknown, but numerous studies have shown that atopy clus-ters in families. It is likely that many different genes areresponsible for an individual’s predisposition to allergy andthat exposure to certain known and unknown allergensleads to the expression of asthma, eczema, or hay fever.Twin studies have also been useful in estimating the relativeimportance of genes and environment on atopy, includingeczema (Schultz Larsen, 1993; Lichtentstein and Svarteng-ren, 1997; Strachan et al, 2000). Studies based on morethan 3000 UK female twins have shown heritability esti-mates for eczema of 60%, with models being in favor of acombination of additive genes and unique environment (Mi-kkilineni et al, 2001). Candidate gene approaches for puta-tive atopy genes have already been conducted by manygroups in diverse populations, mainly using the family de-sign (Ono, 2000). Many genes appear to have modest ef-fects on the risk of atopy, and using genome-wide scansmany chromosomal regions have been linked to the risk ofatopy.
The study published in this issue by Brydl et al assessesthe relative effects of genes and environment on the nickelallergy in a large population-based sample of female twins.Nickel allergy is a very common disorder affecting 30% ofthe population with a rising incidence, especially in femaleswho have previously had skin piercing. The potential asso-ciation between nickel allergy and atopy is controversial, assome studies have shown that nickel allergy is more prev-alent in some atopic patients, whereas others have shownno association. Positive prick tests and IgE levels have notbeen shown to be associated with nickel allergy. Allergiccontact dermatitis is dependent on cell-mediated immuneresponse mediated mainly by type 1 lymphocytes, whereasatopic dermatitis is the result of sustained activation of type2 lymphocytes, but little is known about the true relationshipbetween nickel allergy and atopy. Another potential link be-tween atopy and nickel allergy is the altered barrier functionin patients who have atopic hand dermatitis, which mayallow greater risk of contact allergy and therefore perpet-uate the hand dermatitis. The twins in the study reportedhere were first recruited on the basis of having ‘‘hand ec-
zema’’. Clinical symptoms of hand dermatitis may be themanifestation of allergic contact dermatitis, irritant con-tact dermatitis, and atopic eczema—which may includedishydrotic eczema—thus the background phenotype ofinclusion in this study may be very heterogeneous. Theauthors conclude that nickel allergy is unlikely to have agenetic basis because of the lack of a greater correlation inidentical pairs compared with non-identical pairs.
Twin studies are ideally suited to dissecting genetic andenvironmental influence on a disease or trait, as opposed tofamily studies that are confused by common environmentalinfluences that cannot clearly be separated from sharedgenes. But the estimates yielded by twin studies, however,are only applicable to the population studied and the meth-od of ascertaining the twin pairs will also have a significantinfluence on the results. The study presented here by Brydlet al recruited highly selected twin pairs on the basis of oneof the twins having had a history suggestive of ‘‘hand ec-zema’’. Six hundred and thirty female twins who fulfilled thecriteria for inclusion were selected from the Danish TwinRegistry. On a background of ‘‘hand eczema’’, the authorsassessed the potential genetic influence on nickel allergy bypatch testing. Although it is possible that nickel allergy ismostly influenced by environmental factors, the fact that thetwins were recruited on the basis of a variable phenotype ofhand eczema may have affected the results and interpre-tation. The sample size in each age group is also small andthe power to discriminate genetic and environmental effectsmay also be an issue. This study has concluded that given agenetic susceptibility to atopy, there is no major additionalgenetic component to nickel allergy. Although it is evidentthat environmental factors such as ear piercing are impor-tant, as the prevalence of nickel allergy is much lower inmen, the fact that only a proportion of the female populationdevelops allergy to nickel suggests that genetic factors mayalso play a role. Studies have also shown some familialclustering in nickel allergy, supporting a genetic basis (Fle-ming et al, 1999). If the specific question about the true roleof genes and environment in nickel allergy needs validation,the study should be repeated in an unselected random twinpopulation of sufficient size.
DOI: 10.1111/j.0022-202X.2004.23508.x
References
Brydl LE, Hindsberger C, Kyvik KO, Agner T, Menne T: Genetic factors in nickel
allergy evaluated in a population-based female twin sample. J Invest
Dermatol 123:1025–1029, 2004
Copyright r 2004 by The Society for Investigative Dermatology, Inc.
xxiv
Cookson WO, Moffat MF: The genetics of atopic dermatitis. Curr Opin Allergy
Clin Immunol 2:583–587, 2002
Fleming CJ, Burden AD, Forsyth A: The genetics of allergic contact hypersen-
sitivity to nickel. Contact Dermatitis 41:251–253, 1999
Lichtentstein P, Svartengren M: Genes, environments and sex: Factors of im-
portance in atopic diseases in 7–9 year old Swedish twins. Allergy 52:
1079–1086, 1997
Mikkilineni R, Strachan D, Snieder H, Spector TD, Bataille V: A twin study of
eczema and other atopic disorders in a large UK female population.
J Invest Dermatol 117:758, 2001
Ono SJ: Molecular genetics of allergic diseases. Annu Rev Immunol 18:347–366,
2000
Schultz Larsen F: Atopic dermatitis: A genetic–epidemiology study in a popu-
lation based twin sample. J Am Acad Dermatol 28:719–723, 1993
Strachan DP, Wong HJ, Spector TD: Concordance and interrelationship of atopic
diseases and markers of allergic sensitisation among adult female twins.
J Allergy Clin Immunol 108:901–907, 2001
GENETIC FACTORS IN NICKEL ALLERGY xxv123 : 6 DECEMBER 2004
