Dermatitis herpetiformis.

Dermatitis herpetiformis (DH) is a cutaneous manifestation of coeliac disease (CD), which causes an itching and blistering rash, typically on the elbows, knees and buttocks. DH and CD share a similar genetic background, small bowel mucosal alterations, and an autoimmune response against tissue transglutaminase in the serum and small bowel. DH is typically diagnosed during adulthood, and it is slightly more common among males than females. The incidence of DH seems to be decreasing, in contrast to the detected four-fold increase in the incidence of CD. In addition to typical clinical picture, diagnosis of DH relies on the demonstration by direct immunofluorescence of pathognomonic granular IgA deposits in the papillary dermis. Circulating tissue transglutaminase antibodies support the diagnosis, but their absence does not exclude DH. Obtainment of small bowel mucosal biopsies is not necessary when DH is diagnosed, but if performed, the majority of patients are found to have villous atrophy, and even those with normal villous architecture evince CD-type inflammation. The treatment of choice in DH is a strict, life-long adherence to a gluten-free diet (GFD). In addition to alleviating the symptoms of DH and healing the small bowel mucosal damage, a GFD increases the quality of life for patients, and decreases the risk for lymphoma in DH. Further, the mortality rate of patients with DH treated with a GFD seems to be lower than that of the general population. However, as changing to a GFD has a rather slow effect on the DH rash, patients with severe skin symptoms should additionally be treated with dapsone medication. This review article is based on a presentation given at the British Society for Medical Dermatology blistering skin diseases meeting 2019.