Malignant Evolution of Asymptomatic Monoclonal IgM after Seven and Fifteen Years in Two Siblings of a Patient with Waldenström's Macroglobulinemia

This paper reports a rare familial occurrence of Waldenström's macroglobulinemia (WM) in siblings (two brothers and one sister). Examination of the siblings of a patient suffering from WM in 1965 showed that a brother and a sister had an “asymptomatic” monoclonal IgM in their sera without clinical or hematological features. Follow‐up demonstrated a malignant transformation into WM after 7 years in the brother and after 15 years in the sister. This unusual incidence makes the true existence of asymptomatic gammopathies of IgM class questionable.