Multicentric Castleman disease and systemic lupus erythematosus phenotype in a boy with Klinefelter syndrome: long-term disease stabilization with interferon therapy.

An 11-year-old boy with Klinefelter syndrome had Castleman disease (CD) of plasma cell type develop. Nonregulated antibody production mimicked systemic lupus erythematosus (SLE). Hepatitis C virus (HCV) infection caused significant disease worsening. The patient was treated with a daily dosage of 2 million units/m2 of IFN-alpha. Dramatic clinical improvement and decreasing autoimmune phenomenon were observed. HCV RNA were cleared. Hypergammaglobulinemia did not change. The boy has been living for 8 years with his disease. Plasma cell type CD can mimic collagenosis. Disease worsening is caused by HCV, though it can be reversed with IFN-alpha. Klinefelter syndrome may be a genetic susceptibility factor for CD in some cases.