Purpose: Because the clinical significance of immunoglobulin abnormalities reported in relatives of familial Waldenström macroglobulinemia (WM) patients is unknown, we initiated a follow-up study of three WM families originally evaluated 27 years previously.
Experimental design: Of 29 eligible first-degree relatives of WM patients, 27 (93%) had originally participated in clinical and electrophoretic evaluations. We re-contacted all participants for prospective follow-up electrophoretic analysis and other studies.
Results: Initially, five relatives had IgM monoclonal gammopathy (IgM MG), and four had IgM polyclonal gammopathy (PG). Twenty-two relatives (81%) were re-evaluated. Median follow-up was 17 years (range, 7-27). At re-contact, all IgM MG persisted or progressed, including three that evolved to WM. Among the four with PG, two new IgM MG cases developed. Overall, seven relatives (26%) had IgM MG, and five (18%) had IgM PG.
Conclusions: Although based on small numbers, this study provides the longest comprehensive follow-up of WM families to date. IgM MG seems to be a phenotypic marker of WM susceptibility in some families and may have a high risk of progression to WM. IgM PG may also be important in WM families. These observations require validation in larger studies and, if confirmed, may be used to identify a cohort (relatives with IgM MG) for future prevention strategies.