Familial Waldenström Macroglobulinemia: Families Informing Populations.

Familial clustering of Waldenström macroglobulinemia (WM) has been observed for nearly 6 decades. Family studies have provided seminal observations in delineating the phenotypic spectrum of WM susceptibility and confirming the importance of immunoglobulin M (IgM) monoclonal gammopathy of undetermined significance (IgM MGUS) as a precursor condition for WM, providing the rationale for large population-based epidemiologic studies of IgM MGUS and WM, and providing both the basis and the material for ongoing genetic studies aimed at identifying WM predisposition genes. Together, these investigations may help elucidate the host factors underlying WM development.