Multiple myeloma with serum IgM kappa and Bence Jones lambda biclonal gammopathy.

We report a rare finding: IgM kappa and Bence Jones lambda double gammopathy in serum of a 80-year-old man with untreated symptomatic multiple myeloma. The unusual findings are confined to the laboratory studies demonstrating also a Bence Jones lambda proteinuria, high erythrocyte sedimentation rate (113 mm/h), and anemia. The synthesis of the different light chains seems to occur in separate cellular clones.