[Biclonal light chain gammopathy in multiple myeloma--a case report].

A 74-year-old woman was admitted to our hospital in March 1998 for low-back pain. In 1990, she had a chemotherapy for diffuse mixed cell lymphoma. Biochemical and serologic assays revealed a total protein level of 9.7 g/dl and an IgG level of 4,530 mg/dl. Immunoelectrophoresis showed monoclonal IgG protein associated with two monoclonal kappa and lambda light chain components. Bone marrow examination showed proliferation of myeloma cells comprising up to 25% of all nucleated cells. Myeloma cells were immunohistochemically positive for IgG and kappa and lambda light chains. IgG contained equal amounts of IgG 1 and IgG 2 subtypes and the complementarity determining region 3 (CDR 3) of myeloma cells showed oligoclonality by polymerase chain reaction, suggesting the myeloma cells may have two components. The patient received melphalan and prednisone in combination, resulting in only a minor response. She eventually developed angioimmunoblastic T-cell lymphoma. Biclonal gammopathy associated with malignant lymphoma is rare in case of multiple myeloma and may provide some insight into the pathogenesis of plasma cell tumors.