Multiple myeloma in two brothers. Immunoglobulin levels among their relatives.

The reports on the occurrence of myeloma in two or more members of the same family are very scanty, and until present, only about twenty observations of the familial occurrence have been reported. In this paper the observation of multiple myeloma in two brothers is described. The clinical diagnosis was confirmed by the bone marrow biopsy which showed an infiltration of abnormal plasma cells. X-ray examination of the skeleton revealed typical osteolytic changes in one patient and diffuse osteoporosis in the other. Moreoever both patients had a massive monoclonal protein fraction in serum and Bence-Jones protein in urine. In one case the monoclonal serum protein was of the IgG-K type and in the other, of the IgA-K type. Thus the antigenic determinants were different in the class specificity. Immunoglobulin studies among healthy relatives of the two brothers demonstrated much higher incidence of the polyclonal increase in one immunoglobulin class than could be expected in the population. Without evidence of monoclonal serum protein, unusally high IgA serum levels, more than 500 mg/100 ml, were observed in seven of seventeen healthy family members. This could be explained on genetic basis in connection with the familial occurrence of myeloma either by an abnormal distribution of plasma cell clones or by their abnormal activity. However, a defective control mechanism in protein synthesis may also be taken into consideration.