A male patient was observed for seven years, from the onset of neurologic symptoms to removal of a left atrial myxoma. Mild broad-based elevation of the serum γ-globulin level with a normal bone marrow aspirate was seen early in the course of disease. The broad-based γ-globulin level increased, and at the time of surgical removal of the tumor, the patient was found to have a monoclonal increase of K light chain IgG with 60% infiltration of the bone with immature plasma cells. The findings are consistent with the view that continuous immunologic stimulation by products of the atrial tumor resulted in malignant transformation of immunocytes with resulting IgG multiple myeloma.
(Arch Intern Med 139:116-117, 1979)