Reports of sibling pairs with multiple myeloma (MM) suggest that occasionally, genetic factors may predispose to myeloma, and Hemminki (2002) reported that offspring of multiple myeloma cases had a fourfold increased risk of disease. Horwitz et al. (1985) reviewed 30 families with two affected siblings and a further nine families with three affected siblings. In two reports of twins with multiple myeloma (Judson et al. 1985; Comotti et al. 1987), one emphasized the contribution of shared environment and the other genetic factors. A 2 % incidence of plasma cell disorders in siblings of myeloma patients has been reported, but this may not be excessive (Horwitz et al. 1985). There have been a few families described with several cases of MM, although these are rare (Lynch et al. 2008b). Lynch et al. (2001) described a large kindred with familial multiple myeloma in three cases and a monoclonal gammopathy of unknown significance in two further relatives.
Although there is no case for routine screening of relatives of myeloma patients, when familial myeloma is found, first-degree relatives should be screened (by blood and urine electrophoresis) and those with benign monoclonal gammopathy kept under surveillance. There is evidence for an increased relative risk of multiple myeloma in relatives of MM cases (SIR 2.45), chronic lymphatic leukemia (2.45), and non-Hodgkin lymphoma (1.34) (Altieri et al. 2005). A hereditary predisposition to B cell proliferative diseases has been established, and IgG/A and IgM disorders may occur together in families, where enhanced B cell responsiveness may be found in healthy subjects clustered around cases (Steingrimsdottir et al. 2011).