[Familial myeloma. Apropos of a case].

2 cases of multiple myeloma, both with IgG kappa, are reported in a man and his daughter. 33 other cases of myeloma involving two or more first degree relatives have been reported in the literature. Reported cases showed no major specific characteristics of the myelomas involved. Monoclonal protein family members were rarely identical. Our observation of identical monoclonal protein in two family members has only been found in 4 other reports. Occurrence of several cases of myeloma in one family is unlikely to be due to chance alone and the possibility of familial myeloma must be considered. Reports of benign monoclonal gammapathy in other members of the family of a patient with myeloma is also in favor of genetic factors. HLA-typing has shown an increase in frequency of the 4c complex and HLA-A9 in myeloma, and the latter was present in our patients. A genetic predisposition is further supported by experimental observations in mice. Finally, the short delay between onsets of myeloma in family members, less than 5 years in 20 families out of 27, and 4 years in our case, suggests a possible role of environmental factors.