Which histopathologic features are typical of bullous pemphigoid?

• A. Subepidermal blisters with linear IgG/C3 along basement membrane
• B. Suprabasal acantholysis
• C. Full-thickness epidermal necrosis
• D. Intraepidermal edema with spongiosis

Answer: (A)

Bullous pemphigoid is an autoimmune blistering disease where antibodies target components of the basement membrane zone, especially hemidesmosomes. This causes separation right below the epidermis, producing subepidermal blisters. A key histologic picture is a relatively intact epidermis sitting on a dermal inflammatory infiltrate rich in eosinophils, with the blister roof formed by the overlying epidermis. Direct immunofluorescence adds the hallmark: a smooth, continuous line of IgG (and often C3) along the basement membrane.

This matches the described pattern: blisters forming beneath the epidermis (subepidermal) and linear deposition of IgG and complement at the dermal-epidermal junction. In contrast, other patterns point to different diseases—for example, suprabasal acantholysis seen in pemphigus vulgaris involves the epidermal layers, not a subepidermal split; full-thickness epidermal necrosis occurs in severe reactions like toxic epidermal necrolysis; and intraepidermal edema with spongiosis is typical of eczematous or inflammatory dermatoses, not BP.