CD40LG and plasmacytoma: MGUS is further classified into three subtypes that include (1) non-IgM MGUS (IgG, IgA, or IgD MGUS), the most common subtype with an increased propensity to progress to MM, solitary plasmacytoma, and AL amyloidosis; (2) IgM MGUS, which accounts for approximately 15% of cases, with an increased propensity to progress to Waldenstrom macroglobulinemia, AL amyloidosis, and, rarely, IgM MM; and (3) light-chain MGUS, a subtype in which secreted M-proteins lack the heavy-chain component of immunoglobulin, with a risk of progression to light-chain MM and AL amyloidosis [3,4].