Familial macroglobulinemia in a Lebanese family with two sisters presenting Waldenström's disease.

We report a non-consanguineous family with ten children, in which two sisters were found to have Waldenström's disease with light chain IgM monoclonal components. Immunoglobulins were examined in four siblings and revealed high serum IgM concentrations with no monoclonal component. This additional case of familial Waldenström's macroglobulinemia stresses the usefulness of screening family members of patients with monoclonal gammopathy since they may be at high risk of developing the disease.