Dermatitis herpetiformis :

Dermatitis herpetiformis (DH) is a rare blistering disorder associated with gluten-sensitive enteropathy (coeliac disease). DH and celiac disease are associated with other organ-specific autoimmune disorders.
Skin biopsy shows a subepidermal blister with neutrophil microabscesses in the dermal papillae. Direct IMF studies of uninvolved skin show IgA in the dermal papillae and patchy granular IgA along the basement membrane. The jejunal mucosa usually shows a partial villous atrophy.
Clinical features
Dermatitis herpetiformis is commoner in males and can present at any age but is most likely to appear for the first time in young adult life. It presents with intensely itchy, small blisters of the skin. The lesions have a predilection for the elbows, extensor forearms, scalp and buttocks. The tops of the blisters are usually scratched off; thus crusted erosions are often seen at presentation. Remissions and exacerbations are common.
Treatment
This should always be with a gluten-free diet (GFD). Control of the skin disease can be obtained with oral dapsone (50-200 mg daily) or sulphonamides. If a strict GFD is adhered to, oral medication can often be withdrawn after 2 years. The GFD will need to be lifelong. It protects against the rare complication of small bowel lymphoma.
Use of dapsone.
Dapsone frequently causes a mild, dose-related haemolytic anaemia but the haemolysis can be devastating if there is G6PD deficiency. Liver damage, peripheral neuropathy and aplastic anaemia can also rarely occur, so regular monitoring of a blood count and liver function is needed.