As so defined, light chain MGUS comprises ~19% of all MGUS cases, occurs in ~0.8% of the general population, and progresses to light chain multiple myeloma at the very slow rate of 0.3 cases per 100 years.Some early studies have reported that a very rapid rate of progression occurs in light chain MGUS patients who have free light chain κ/λ or λ/κ ratios equal to or greater than 100 (i.e. and κ/λ ratio outside of 0.02 to 100). About 80% of individuals bearing these light chain ratios were found to progress to light chain multiple myeloma within 2 years. In consequence, these individuals were recommended for being diagnosed and treated as having light chain multiple myeloma. However, two more recent studies reported a 2-year progression rate for these patients of 64% and 30%. It is therefore suggested that the diagnosis of light chain multiple myeloma based solely on a free κ/λ light chain ratio of 0.02 to 100 may be premature. Monoclonal gammopathy of renal significance
Monoclonal gammopathy of renal significance or MGRS designates any MGUS disorder that has a clinically significant impact on renal function. MGRS can be caused by the deposition of a monoclonal immunoglobulin in, and consequent injury to, the kidneys. The diagnosis of this form of MGRS is made based on the presence of: 1) a disorder meeting the criteria for MGUS; b) decreased kidney function as evidence by, e.g.
Plasma Cell Myeloma with concomitant chronic Lymphocytic Leukemia/monoclonal B-Cell Lymphocytosis
Multiple myeloma occurring concurrently with chronic Lymphocytic Leukemia or its pre-malignant precursor, monoclonal B-cell lymphocytosis, is an extremely rare condition in which patients evidence findings of the  plasma cell dyscrasia plus either one of the cited clonal lymphocytic diseases. Patients are typically elderly (median age of 74, range 42–91 years old) males (51 of 66 case reports) and commonly present with a combination of symptoms related to chronic lymphocytic leukemia symptoms (fatigue, autoimmune hemolytic anemia, enlargements of liver and/or spleen and lymphadenopathy) plus symptoms of multiple myelomas. Patients exhibit two distinct populations of clonal cells in their bone marrow, blood, and/or other tissues: plasma cells, which may have an immature plasmablastic morphology and small lymphocytes, which have a morphology typical of chronic lymphocytic leukemia cells. Patients blood and/or urine evidences a plasma cell-derived myeloma proteins, either IgG, IgA, or free light chain in ~50%, 20%, and 20% of cases, respectively, but may also have a second myeloma protein made by the lymphocytic cells, either an IgM or IgG. Signs and symptoms of chronic lymphocytic leukemia commonly precede those of multiple myeloma, sometimes by years. The relationship between the two clones of cells in this combined disease has not been established although one study suggests that the clonal plasma cells and clonal lymphocytes arise from a common hematological stem cell.