Prominent intraepidermal and dermal eosinophils as a clue to the diagnosis of pemphigus herpetiformis: A case series and literature review

Summary: Introduction: Pemphigus herpetiformis (PH) is a rare pemphigus variant characterized by pruritic, annular urticarial plaques and vesiculobullous lesions with direct immunofluorescence (DIF) findings of pemphigus. The histologic findings are characterized by review of 3 cases. Case 1: 61 y.o. female with annular urticarial erythematous plaques with superficial erosions and bullae on the legs. Biopsy demonstrated intraepidermal vesicles, minimal acantholysis, and numerous eosinophils with IgG and C3 epithelial cell surface deposition. Treatment included dapsone and mycophenolate mofetil. Case 2: 75 y.o. male with a 15-year history of a generalized urticarial rash; biopsies demonstrated eosinophilic spongiosis, eosinophils abutting the basement membrane, and IgG/C3 epithelial cell surface deposition. Treatments included doxycycline with niacinamide. Case 3: 62 y.o. male with diffuse annular plaques and vesiculobullous lesions had intraepidermal vesicles containing numerous eosinophils, marked eosinophilic spongiosis, and strong IgG epithelial cell surface deposition. Treatment included doxycycline and niacinamide. Conclusion: Consistent PH histopathologic features identified include abundant intraepidermal and dermal eosinophils and eosinophilic spongiosis. This series highlights the importance of including PH in the differential diagnosis of abundant eosinophils in the epidermis or dermis. Accurate diagnosis is essential as PH typically follows a benign course and responds to anti-inflammatory agents like doxycycline and dapsone.