IgM monoclonal gammopathy

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The differentiation between multiple myeloma and macroglobulinemia is usually not difficult. However, occasionally a patient will have presenting symptoms common to both diseases.1–8 Furthermore, macroglobulinemia may be associated with lymphocytic lymphoma, chronic lymphocytic leukemia, or an additional monoclonal spike.9–31 A “benign” IgM monoclonal gammopathy may also occur. The incidence of such intermediate syndromes and their prognostic significance is not well established.

This paper reviews 28 cases of IgM monoclonal gammopathy seen at the Cleveland Clinic; the histopathologic spectrum and clinicopathologic correlates are emphasized.

Materials and methods

The records of 28 patients who had immunochemical studies compatible with IgM monoclonal gammopathy were reviewed. Representative blood smears, bone marrow aspirates or biopsy specimens or both were examined, as well as any other available surgical and necropsy material. Peripheral blood smears were examined for the presence of rouleau and unusual white cell morphology. A 500-cell count differential was done on each marrow aspirate, unless it was extremely hypocellular. One hundred cell counts or qualitative estimates of dominant cell type were made on hypocellular specimens. The dominant marrow proliferating cell type was identified as plasmacytic, mature lymphocytic, or intermediate (“plasmacytoid lymphocyte” with an eccentric nucleus, clumped chromatin, and absence of a paranuclear halo). Protein electrophoresis was per-formed on cellulose acetate using the Beckman microzone system with B-2 buffer (pH 8.6), Beckman fixative-dye solution (Ponseau-S, trichloracetic acid, sulfosalicylic acid), and was read in the Beckman densitometer at 520 n m. Immunoelectrophoresis was performed in a Buchler electrophoretic chamber with a Heathkit power supply applying 90 . . .



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