Biclonal IgM gammopathy in chronic lymphocytic leukemia.

The association of chronic lymphocytic leukemia (CLL) with serum paraproteinemia (ie, monoclonal immunoglobulin production and secretion) is well known. We, however, could find only three previous reports of CLL where multiple serum paraproteins were encountered. We describe a case of biclonal gammopathy in CLL, involving IgM/kappa and IgM/lambda, with each paraprotein reaching serum levels of approximately 10 g/L (1 g/dL). Using immunohistochemical techniques, we identified two morphologically similar lymphocyte populations, which could be stained for either mu and kappa or mu and lambda. The peripheral blood contained a majority of mu/kappa-containing cells (kappa/lambda = 17.5:1), while the bone marrow only contained a modest excess of cells staining for mu/kappa (kappa/lambda = 2.4:1). The clinical significance and prognosis of biclonal IgM gammopathies is uncertain, since so few cases have been reported. Our patient has now been followed up for more than four years.