This elderly man developed non-erythematous blisters along the extensor surface of his forearms. The remainder of his exam was unremarkable. A biopsy was submitted to rule out bullous pemphigoid. Epidermolysis bullosa acquisita (EBA) is a heterogeneous disorder characterized by non-inflammatory bullae. The etiology is unknown, but trauma and sun exposure have been implicated. Autoimmune/systemic diseases show some association. The histology is typical in this case, showing a pauci-inflammatory subepidermal vesicobullous process. The diagnosis is confirmed by immunofluorescence studies. Direct immunofluorescence flindings are similar to bullous pemphigoid, with linear IgG and C3 deposition along the epidermal basement membrane zone. Salt-split skin can be used to distinguish these entities, as EBA will show localization of antibodies to the blister floor, as in our case, and BP will localize to the roof. The differential diagnosis would also include traumatic or suction blisters, but history and immunofluorescence studies should lead to the correct diagnosis.
At higher power, one struggles to find an inflammatory cell. The separation is clean. Immunofluorescence studies helped confirm the diagnosis (not shown).