Overlap of IgG4-related Disease and Multicentric Castleman's Disease in a Patient with Skin Lesions.

A 59-year-old man presented with multiple dark red erythemas with induration, anemia, and polyclonal hypergammaglobulinemia. A skin biopsy revealed the infiltration of lymphocytes and plasma cells and he was initially diagnosed with multicentric Castleman's disease (MCD). Glucocorticoid treatment was only partially effective. Four years later, the patient's bilateral lacrimal glands gradually became enlarged and a biopsy revealed dense lymphocyte and plasma cell infiltration with an IgG4+/IgG+ plasma cell ratio of 70%. The patient was diagnosed with IgG4-related disease (RD). Rituximab only had a slight effect. This case demonstrates that overlapping features of IgG4-RD and MCD may present in a single patient, which suggests a shared pathogenesis.