changing leucine to proline at the 265th amino acid position of the MYK88 protein thereby causing the protein to be continuously active in stimulating the same cell-activating pathways that Toll-like receptors activate intermittently and on a  physiologically basis); b) the CXCR4 gene (8% in IgM MGUS, 25% in IgM-related malignancies); and c) increased gene copy number due to chromosomal rearrangements (36% in IgM MGUS, 82% in IgM-related malignancies). It is clear that each cell type contributes to different features of IgM malignancies but not clear that clonal plasma cells are critical to the development or progression of IgM MGUS. In all events, IgM MGUS is diagnosed in individuals who have serum IgM levels less than 30 gram/liter; have less than 10% of nucleated bone marrow cells with the lymphoplasmacytic morphology, and have no symptoms or findings of end organ dysfunction attributed to Waldenström macroglobulinemia such as anemia, decreases in any white blood cell count, cold agglutinin disease, hyperviscosity of blood, lymphadenopathy, hepatomegaly, splenomegaly, peripheral neuropathy, cryoglobulinemia, or constitutional symptoms.There may be a modest increase in the incidence of IgM MGUS in people of African descent. A study of 213 individuals diagnosed with IgM MGUS found that 10% at 5 years and 24% in 15 years progressed to more serious IgM-related diseases including non-Hodgkin lymphoma, Waldenstorms macroglobulinemia, systemic amyloidosis, and chronic lymphocytic leukemia. A second long-term study of 116 individuals with IgM MGUS found a 15-fold increased risk of progressing to a lymphoid malignancy, mostly to Waldenstorms macroglobulinemia.
Patients are treated similarly to patients suffering the counterparts those with multiple myeloma except that the focus is treating or preventing kidney damage using chemotherapy to reduce production of the monoclonal light chain and thereby stopping, reversing, or preventing kidney injury. Plasma cell leukemia
Plasma cell leukemia is a form of multiple myeloma in which significant numbers of typically immature appearing plasma cells, i.e. plasmablasts, circulate in the blood. Very small numbers of plasma cells may reach the circulation in non-IgM multiple myeloma, non-IgM SMM, and, exceptionally, non-IgM MGUS. In these plasma cell dyscrasias, the presence of even very small numbers of circulating plasma cells is a poor prognostic indicator. In plasma cell leukemia, however, circulating plasma cells reach far higher numbers and at these circulating levels are associated with exceptionally poor  survival rates. The International Myeloma Working Group has defined the diagnostic criteria for plasma cell leukemia as the presence in blood of >2x109 plasma cells per liter or, alternatively, >20% of nucleated blood cells being plasma cells. More recently, the Group has suggested that values of 0.5x109 or 5%, respectively, may be more appropriate from a therapeutic viewpoint and therefore should be studied as a definitive criterion for the disease. A recent study supported this suggestion in finding that multiple myeloma patients with >5% circulating plasma cells had a prognosis much worse than that for multiple myeloma and similar to that for plasma cell leukemia. Flow cytometry immunophenotyping of blood cells to detect clonal phenotypes of plasma cells seen in multiple myeloma (e.g.