Family history of autoimmune disorders and cancer in multiple myeloma.

To explore genetic mechanisms that might underlie the relation observed between multiple myeloma and rheumatoid arthritis, we examined the occurrence of autoimmune disorders in first-degree relatives of myeloma cases and controls. There was a significant excess of rheumatoid arthritis (OR = 3.7; 95% CI = 1.0-13.1) among the relatives of cases compared with controls, as well as an increased occurrence of systemic lupus erythematosus and pernicious anaemia. An excess of certain cancers was also observed among family members, including leukaemia and cancers of the breast, endometrium, and oral cavity and pharynx, but none of the excesses were significant. These findings deserve further evaluation in larger population-based studies.