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A case of multiple myeloma with no monoclonal protein synthesis is reported. The patient had hypogammaglobulinemia, bone marrow invasion, osteolytic lesions, and plasma cell tumors. The absence of protein synthesis has been demonstrated in bone marrow culture with tritiated leucine. No evidence of immunoglobulin production was found. Bone marrow or plasma cell tumor biopsy may be the only method of diagnosis in such cases.

The bone marrow plasma cells of 52 patients with various kinds of monoclonal gammopathies were studied by electron microscopy, and compared to the bone marrow plasma cells of 22 patients with reactive plasmacytosis. Virtually every marrow from patients with myeloma and macroglobulinemia contained plasma cells with disparity between the nuclear maturation and cytoplasmic differentiation. This asynchronous development was not present in plasma cells of reactive marrows nor in plasma cells from patients with megaloblastic anemias. The degree of asynchrony observed in myeloma and macroglobulinemia was proportional to the extent of disease as judged by clinical criteria. For the most part plasma cells of patients with non-myelomatous monoclonal gammopathy failed to exhibit significant asynchrony. These observations are consistent with the view that multiple myeloma is a neoplastic disorder with a definably malignant-appearing cellular proliferation.

The bone marrow of a patient with light chain myeloma and amyloidosis was substantially infiltrated with basophilic globular particles. The globules, which were confined to the bone marrow, ranged in size from tiny intracytoplasmic inclusions to large (100 mu) extracellular particles. Both the intra- and extracellular globules stained with fluorescent antibody directed against the light chain (kappa) produced by the patient's abnormal clone, and not with other fluorescent antiserums. By electron microscopy, even the largest extracytophasmic globules were bounded at least in part by rough membranes, suggesting that their extreme size was the result of cellular synthesis rather than extracellular coalescence.

Two populations of immunologically distinguishable 7S gamma globulins in normal human serum and two corresponding antigenic types of myeloma 7S gamma globulins have been detected with rabbit antiserums to proteins associated with pathological conditions, the differences being related to the H-chains of 7S gamma globulin. No relationship exists with type I and type II antigenic classification, determined by L-chains. Human serums with various hereditary gamma globulin (Gm) specificities contain both types of 7S gamma globulin.