In contrast, IgM-MGUS rarely evolves to an IgM-MM, and more frequently progresses to a subclinical/smoldering Waldenström’s macroglobulinemia (SWM), and WM with a progressive increase in serum IgM M-protein (≥30 g/l) in association with ≥10% infiltration of BM by (clonal) lymphoplasmacytic cells and, in case of WM, also organomegalies [1, 2, 6, 9, 12–16]. The gene discussed is CD40LG; the disease is Waldenstrom macroglobulinemia.