Chapter 8 - Dermatitis herpetiformis -- a cutaneous manifestation of coeliac disease

Abstract

Dermatitis herpetiformis (DH), presenting with an intense itch and blistering symmetrical rash, typically on the elbows, knees, and buttocks, is a cutaneous manifestation of coeliac disease. Overt gastrointestinal symptoms are rare though most patients have villous atrophy in the small bowel, and the rest coeliac-type inflammatory changes. In contrast to coeliac disease, DH affects mostly adults and slightly more males than females. The mean age at onset has increased during the last decades and is at present about 50 years. DH diagnosis is easily confirmed by showing granular immunoglobulin A deposits in the papillary dermis by direct immunofluorescence examination. The DH autoantigen, epidermal transglutaminase (TG3), is deposited at the same site. A valid hypothesis is that the immunopathogenesis of DH starts from hidden coeliac disease in the small bowel with autoantibody responses resulting in deposition of high avidity IgA class TG3 autoantibodies together with the TG3 enzyme in the papillary dermis. The DH-to-coeliac disease prevalence is 1:8. The incidence of DH is slowly decreasing, whereas that of coeliac disease is increasing. The treatment of choice for all DH patients is a gluten-free diet (GFD) in which uncontaminated oats are allowed. At onset, most patients need additional dapsone drug to rapidly control the rash and itching. Dapsone can be stopped after a mean of 2 years, and a strict lifelong GFD alone is required. The long-term prognosis in DH is excellent with a normal quality of life and all-cause mortality.