IgM Myeloma: An IgM Gammopathy Distinct from Waldenstrom's Macroglobulinemia.

A 65-year-old patient with an IgM gammopathy, plasma cell infiltration of the bone marrow, lytic lesions of the skeleton, and symptoms of hyperviscosity was evaluated. A diagnosis of IgM myeloma was made. Treatment for multiple myeloma was initiated and resulted in a significant clinical response. There is ongoing debate whether IgM myeloma exists as a unique entity, oras a variant of Waldenstrom's macroglobulinemia. We reviewed the English literature and discovered only six cases documented as IgM multiple myeloma. Further investigation revealed 30 reported cases, which had characteristics typical of an IgM myeloma, but were documented as variations of B-cell neoplastic disease. We acknowledge IgM myeloma to be an entity distinct from Waldenstrom's macroglobulinemia. It is characterized by an IgM monoclonal gammopathy, a predominance of plasma cells infiltrating the bone marrow, and typically associated with osteolytic lesions and/or osteoporosis. Recognizing IgM myeloma is necessary for appropriate disease management.