Body mass index and prevalence of skin diseases in adults with untreated coeliac disease.

OBJECTIVE Coeliac disease (CD) is associated with immune-mediated skin diseases such as dermatitis herpetiformis and others. The objective of the study was to investigate the relation of body mass index (BMI), as an index of absorptive status, with the prevalence of skin diseases in adults with untreated CD. METHODS Anthropometry, gastro-intestinal symptoms, nutritional indices and immune-mediated skin diseases (dermatitis herpetiformis, psoriasis, aphthosis and alopecia) at diagnosis were analysed. RESULTS 223 men and 924 women with untreated CD (aged 20-60 years) were included, the commonest skin disease was dermatitis herpetiformis (18.4 and 6.9%, respectively), the rarest one was alopecia (1.8 and 2.1%). The BMI was positively associated with male gender, age at diagnosis and nutritional indices, negatively with diarrhoea and dyspepsia (p < 0.001). A BMI difference of 3.5 (1 standard deviation) was related to an excess prevalence of dermatitis herpetiformis (odds ratio, OR = 1.46, 95% confidence interval, CI = 1.23-1.72) and of psoriasis (OR = 1.40, 95% CI = 1.10-1.79) but not of other immunological disorders. Findings were similar in analyses by gender or age group and controlled for gender and age. The relation of BMI to dermatitis herpetiformis was linear over the whole BMI range, also excluding overweight patients. The relation of BMI to psoriasis was flat for low-to-normal BMI and explained only by overweight patients. CONCLUSION In CD at diagnosis, the BMI is positively related to the prevalence of dermatitis herpetiformis and psoriasis, not to that of other immune-mediated skin diseases.