Track

Case Reports

Abstract

A 77-year-old woman presented with a 20-year history of a 20-cm, solitary plaque on the anterior distal thigh. The lesion was asymptomatic, but its persistence was bothersome to the patient. Clinically, the differential diagnosis included eczema and vasculitis. Biopsy of the lesion 2 years prior to this presentation resulted in a diagnosis of “cutaneous lymphoid hyperplasia with plasmacytosis.” Repeat incisional biopsy showed a dermal tumor composed of nodular aggregates of plasma cells, lymphoid aggregates containing rare germinal centers, eosinophils, storiform fibrosis, and obliterative phlebitis. Immunohistochemistry demonstrated an IgG4-to-IgG ratio of 90%. In situ hybridization studies demonstrated polytypic light chain expression. Subsequently, serologic testing was pursued and revealed an elevated IgG4 level. Further systemic evaluation found no evidence of extra-cutaneous disease. A final diagnosis of primary cutaneous IgG4-related disease (IgG4-RD) was made. While rare, this case serves as a reminder to keep the entity of IgG4-RD in the differential diagnosis when encountering a persistent plaque with concern for a cutaneous pseudolymphoma. It also serves to highlight the finding of obliterative phlebitis in a primary cutaneous presentation of IgG4-RD. Obliterative phlebitis is a key pathological feature of IgG4-RD; however, its presence in skin-related disease is uncommon. Finally, cutaneous IgG4-RD most commonly affects the face, neck, upper extremities, and torso. Here, we report a case on the lower extremity, adding a rare location to the pool of cases in the literature.