A 40-year-old man was admitted because of left hypochondralgia, generalized lymphadenopathy and hepatosplenomegaly. The white-cell count was 31,400/cmm with 93% lymphoid cells. The bone marrow aspirate showed normocellularity with 70.8% lymphoid cells. The lymphoid cells in the peripheral blood were positive for Ia-like antigen and surface membrane immunoglobulins (SmIg), but negative for cytoplasmic immunoglobulins (CIg). M-component (IgM-κ, 1,400 mg/dl) was detected in the serum. From these findings, the patient was initially diagnosed as having B type chronic lymphocytic leukemia (clinical stage II) with IgM-κ type M-component. Three and a half years later, laboratory examination showed the following values: the serum M-component, 3,686 mg/dl; lymphoid cells in the blood, 3,953/cmm; and urinary Bence Jones (κ) proteins, 50 mg/dl. Lymphadenopathy and hepatosplenomegaly was essentially unchanged. The morphology of lymphoid cells showed no change. The lymphoid cells that were positive for IgG-, C3b-receptors, HLA-DR and B1 antigen had both monoclonal SmIgM-κ and monoclonal CIgM-κ. On electron microscopic studies, lymphoid cells showed some differentiation toward plasma cells.
Thus, the patient was diagnosed as having primary macroglobulinemia rather than chronic lymphocytic leukemia. No relation was found between the number of tumor cells and the amount of serum M-component. The present case is illustrative of the process of B lymphocyte differentiation.
