Concordance of dermatitis herpetiformis and celiac disease in monozygous twins

Celiac disease can be defined as the classical manifestation of gluten sens itivity, which primarily affects the small intestine. Gluten sensitivity ha s also a skin manifestation, i.e., dermatitis herpetiformis, Both diseases have a strong genetic association with HLA DQ on chromosome 6, In this stud y we tried to estimate how much different clinical expressions of gluten se nsitivity are determined by genetic factors, and hence how feasible they ar e for genetic mapping; therefore, we studied all six monozygous twin pairs found among 1292 prospectively collected patients of dermatitis herpetiform is in Finland, Three of the six twin pairs were concordant for dermatitis h erpetiformis and for simultaneous enteropathy, celiac disease. Two other tw in pairs were partially discordant, one of each pair had dermatitis herpeti formis and celiac disease, whereas the other had solely the gut manifestati on of gluten sensitivity, i.e,, celiac disease. Only one pair was found to be discordant for gluten sensitivity, All the pairs had typical risk allele s for gluten sensitivity, i.e., either HLA DQ2 or DQ8, These results demons trate that the genetic component in gluten sensitivity as broadly defined i s very strong (5/6 concordant), Genetically identical individuals can have clearly distinguished phenotypes, either dermatitis herpetiformis or celiac disease, suggesting that environmental factors determine the exact phenoty pe of this multifactorial disease. These findings are of importance in gene tic linkage analyses, which focus to only certain phenotypic properties of a complex trait.