IgG-associated immune thrombocytopenia in Waldenström macroglobulinemia.

Waldenström macroglobulinemia (WM) is characterized by serum IgM monoclonal gammopathy, and only occasionally complicated by immune thrombocytopenia. Rarely, coexistence of non-IgM gammopathy in WM has been reported. Herein, we describe an 81-year-old case of WM with rapidly progressive immune thrombocytopenia accompanied by concurrent IgG gammopathy and elevation of platelet-associated IgG (PA-IgG). Immunostaining of the bone marrow specimen displayed not only IgM positive but also IgG positive plasmacytoid cells. Although dexamethasone therapy had no effect on thrombocytopenia, a modified RCD regimen (rituximab 375 mg/m(2) i.v. day 1, cyclophosphamide 375 mg/m(2) i.v. day 2 and dexamethasone 12 mg/body orally days 1-7) successfully normalized PA-IgG as well as IgG and IgM paraproteinemia and significantly increased platelet count. The current case suggests that the IgG gammopathy associated with WM is likely to be an etiology of immune thrombocytopenia and that tumor reduction, rather than immunosuppression, leads to an improvement of concurrent thrombocytopenia.