IgA nephropathy associated with Castleman disease with cutaneous involvement.

A 35-year-old Japanese man developed systemic lymphadenopathy during the course of immunosuppressive therapy for IgA nephropathy associated with cutaneous nodules, polyclonal hypergammaglobulinemia, and persistent increased serum C-reactive protein of unknown cause. Lymph node examination showed the plasmacytic type of Castleman disease (CD). A skin biopsy showed specific pathologic findings of CD cutaneous involvement. Considering the involvement of interleukin-6 in CD, we treated the patient with humanized anti-interleukin-6 receptor antibody. Thereafter, his symptoms and abnormal laboratory findings were improved. Cutaneous CD has rarely been described in Asian population, and renal complications in CD are uncommon and heterogeneous. To our knowledge, this is the first case of IgA nephropathy associated with multicentric CD with cutaneous involvement.