Case 1: A subepidermal blister is seen with underlying eosinophils and neutrophils in the dermal papillae.

Case 2: This different case clearly demonstrates a subepidermal cleft.

Note the presence of neutrophils, lymphs and eosinophils, some forming microabscesses. There is also some vasculitis.

The neutrophils tend to collect at the dermal papillae.

Dermatitis herpetiformis (DH) is a chronic pruritic skin disease that develops largely in patients with latent gluten-sensitive enteropathy (celiac disease). There is an association with HLA haplotypes D8 and DR3 (Rapini, Busam). Unlike other bullous disorders, DH patients have no circulating autoantibodies binding to the dermal basement membrane or other structures of the skin, but they have gluten-induced IgA autoantibodies against transglutaminase 2 and 3.

Histologically, DH may be difficult to distinguish from bullous pemphigoid and linear IgA bullous dermatosis. In all these entities, there is a subepidermal blister with microabscesses of neutrophils and eosinophils in the dermal papillae. Linear IgA deposition is present along the epidermal basement membrane (linear pattern) in both IgA bullous dermatosis and dermatitis herpetiformis (granular pattern) on immunofluorescence. In DH, the tips of the papillary dermis also have granular deposits of IgA. Clinical history (i.e. vancomycin administration in IgA bullous dermatosis versus gluten sensitivity in DH) is crucial.

Typically presents as intensely pruritic papules and vesicles on the extensor surfaces (elbows, knees, neck) and buttocks.

Gluten-free diet.

Patients with celiac disease have an increased risk of small intestinal adenocarcinoma, esophageal cancer, melanoma, and non-Hodgkin's lymphoma. Patient with DH also have a higher risk of NHL (Hervonen).

→Granular deposits of IgA at the tips of the dermal papillae.

• Epidermis : Bullous Pemphigoid