Dermatitis Herpetiformis: Coeliac Disease of the Skin

Abstract

Dermatitis herpetiformis (DH) is characterized by intense itch and small blisters with predilection sites on elbows, knees and buttocks. The diagnosis of DH is easy because all patients have pathognomonic IgA deposits in the papillary dermis of both involved and uninvolved skin. Patients with DH rarely present with GI symptoms although at least 80% of them have jejunal villous atrophy. Gluten loading causes villous atrophy in the remaining patients showing that also these patients are sensitive to gluten. Interestingly, also the rash responds to gluten withdrawal and relapses on gluten challenge and therefore, a life-long gluten-free diet (GFD) is now the treatment of choice for all patients with DH. The present clinical evidence shows that the skin-gut relationship is very close in DH but the pathomechanism of the rash remains open. IgA disapppears rarely from the skin during GFD treatment, and all efforts to show gluten in the skin or to characterize the antigen for IgA have failed Immunogenetic and family studies have produced further evidence that DH seems to be only a specific skin manifestation of coeliac disease. The HLA pattern in DH is similar to that reported in coeliac disease and DH patients seem to have as often affected relatives as patients with coeliac disease (CD). In our series of 776 DH patients we found 78 (10%) with affected first-degree relatives. The disease encountered in these relatives was in addition to DH often also coeliac disease. Of the 28 affected sibpairs 14 were DH-coeliac disease and 14 DH-DH pairs, and most of these pairs were concordant for HLA haplotype B8, DR3. We have found also two DH-DH couples whose children have no evidence for DH but have conctracted coeliac disease.