This 46-year-old woman developed markedly pruritic papules and vesicles on her hands, elbows and knees. She had a recent upper respiratory infection for which she took an antibiotic (Levaquin). The clnician was suspecting linear IgA dermatosis, bullous pemphigoid, or pseudoporphyria. This is a good example of an adult-onset linear IgA dermatosis. The etiology is unknown, but there are associations with autoimmune disorders and drugs. The histology is characterized by neutrophils aligning along the dermal/epidermal junction. In this case, the neutrophils were accompanied by eosinophils, which is not uncommon and can raise the suspicion for bullous pemphigoid. Direct immunofluorescence helped by showing the characteristic linear pattern of IgA along the epidermal basement membrane zone (not shown). The clinical and histopathologic features may resemble dermatitis herpetiformis, which is the major diagnosis in the differential. Taken together, the clinical history, histology and immunofluorescence should lead to the correct diagnosis.
Histologic sections of skin show separation of the epidermis from the dermis in a subepidermal plane. Within the papillary dermis and the blister cavity, there are numerous neutrophils with admixed eosinophils. Well-formed papillary microabscesses are not appreciated.