The occurrence of type 1 diabetes in patients with dermatitis herpetiformis and their first-degree relatives

BACKGROUND: The increased prevalence of type 1 diabetes (T1D) is well documented in patients with coeliac disease, whereas evidence is scanty in patients with dermatitis herpetiformis (DH). OBJECTIVES: To assess the prevalence of T1D in patients with DH and their first-degree relatives, and to study how DH patients with associated T1D respond to a gluten-free diet (GFD) treatment. METHODS: A series of 1104 consecutive patients with DH was recorded and a specific questionnaire sent to 341 of these for familial disease surveillance. Sex- and age-matched patients with isolated DH served as controls in the diet treatment analysis. RESULTS: Twenty-five (2.3%) patients with DH were affected by T1D and three (3.0%) of their first-degree relatives also were affected by T1D, the frequencies being significantly higher than in the general population. Most DH patients with T1D and with isolated DH could adhere strictly to the GFD. The response was good or moderate in 84% of the DH patients with T1D and in 94% of the patients with isolated DH. CONCLUSIONS: The prevalence of T1D is increased in patients with DH and their first-degree relatives. The rash in DH patients with T1D responds to a GFD in a way similar to that seen in patients with isolated DH.