[IgM monoclonal gammopathy in plasmacytic neoplasms].

In 331 patients with the diagnosis of multiple myeloma in 4 cases proliferation of plasma cells was associated with synthesis of a monoclonal IgM. In 3 of these cases coexistence was noted of features typical of multiple myeloma and Waldenström's macroglobulinaemia. In the clinical picture in two of these cases sings of blood hyperviscosity prevailed. These patients showed impairment of plasma clotting factors. The count of T and B cells in blood and the adherence and phagocytic activity of monocytes were not abnormal. The ultrastructural pattern of plasma cells in bone marrow was similar to that observed in classical cases of IgG or IgA multiple myeloma. In one case of lymphoplasmocytic proliferation with leucocytosis over 100 x 10(9)/l immunoelectroscopic examination of bone marrow cells demonstrated a formidable accumulation of the heavy chain of mu immunoglobulin in the cytoplasm of lymphoplasmacytes. In the serum and urine no monoclonal protein was found. In this case compression of vertebral bodies Th7 and L2 occurred.