Paraneoplastic pemphigus in association with a retroperitoneal Castleman's disease presenting with a lichen planus pemphigoides‐like eruption. A case report and review of literature

A 50‐year‐old man presented with severe mucosal erosions of the lips, oral cavity and perianal area, a lichen planus‐like eruption on the trunk and extremities and scaly plaques of the palms and soles. The clinical impression was of Stevens–Johnson syndrome, or paraneoplastic pemphigus (PNP). Histopathology revealed vacuolar interface and lichenoid dermatitis with dyskeratosis and suprabasal acantholytic vesiculation. Direct immunofluorescence showed deposition of IgG in the intercellular space and linear deposition of C3 along the basal membrane zone. Indirect immunofluorescence revealed circulating IgG with intercellular staining of the epithelium of rat urinary bladder. Western blotting demonstrated bands of 250‐ and 230‐kDa antigens. The clinical, histological and immunological features were consistent with the lichen planus pemphigoides variant of PNP. A retroperitoneal hyaline‐vascular Castleman's disease was detected and excised. The skin lesions worsened initially after tumour resection but improved gradually, leaving extensive melanosis after cyclosporin and mycophenolate mofetil treatment.