Anatomic Pathology: Skin Pathology

• Dermatitis herpetiformis is an autoimmune blistering skin disorder characterized by severely pruritic, symmetric papules and vesicles located on the elbows, knees, scalp, and buttocks. Epidermal transglutaminase is the major autoantigen in dermatitis herpetiformis.

• Greater than 90% of patients with dermatitis herpetiformis have a gluten-sensitive enteropathy, although only 20% of patients have intestinal symptoms of celiac disease. Ingestion of gluten may provoke flares of the skin disease, so a gluten-free diet is essential. Dapsone is the most effective treatment.

• On histologic examination, dermatitis herpetiformis classically shows neutrophilic microabscesses localized to the dermal papillae, associated with subepidermal blister formation. Eosinophils may be present. Direct immunofluorescence of noninvolved perilesional skin reveals IgA deposition at the dermal-epidermal junction and in the dermal papillae in a granular pattern.

• Linear IgA disease may have identical histologic features to dermatitis herpetiformis because both conditions demonstrate a subepidermal blister with neutrophils. Linear IgA disease typically shows uniform distribution of neutrophils at the dermal-epidermal junction, without papillary microabscess formation. In linear IgA disease, direct immunofluorescence of perilesional skin shows linear staining of IgA at the dermal-epidermal junction, in contrast to the granular pattern seen in dermatitis herpetiformis. Other disorders that may demonstrate a subepidermal blister with neutrophils include bullous lupus erythematosus and inflammatory epidermolysis bullosa acquisita.

• Biopsy specimens to evaluate for dermatitis herpetiformis should include perivesicular skin because the characteristic papillary microabscesses may be seen only at the periphery of a blister. More recent data suggest that anti–epidermal transglutaminase antibodies are a sensitive marker for dermatitis herpetiformis.