SMM consists of the following subtypes which represent progression of their corresponding MGUS subtypes. Non-IgM SMM
Non-IgM SMM (also termed IgG and IgA SMM because of the rarity of IgD and IgE SMM) is diagnosed in asymptomatic individuals based on criteria identical to those listed above for Non-IgM MGUS except that: their intact IgG or IgA myeloma protein levels are equal to or greater than 30 grams/liter rather than 15 grams/liter; their bone marrow shows plasma cells comprise between 10% and <60% rather than <10% of nucleated cells; and/or their 24-hour urine contains 0.5 gram or greater levels of Bence Jones, i.e. light chain myeloma, proteins. individuals must also lack evidence of more recently established multiple myeloma-defining criteria viz., CRAB features, amyloidosis, more than one solitary plasmacytoma, and/or serum or urine free light chain κ to λ or λ to κ ratios of 100 or greater.Overall, the risk of Non-IgM SMM progressing to multiple myeloma is 10% per year for the first 5 years but falls off sharply to 3% per year for the next 5 years and thereafter to 1% per year. Smoldering Waldenström macroglobulinemia
Smoldering Waldenström macroglobulinemia is diagnosed in asymptomatic individuals that have a serum IgM level 30 gram/liter and/or a bone marrow lymphoplasmacytoid cell infiltrate >10% of total nucleated cells.
MGUS is categorized into the following sub-types based upon the identity and levels of the myeloma proteins detected as well as the prognoses for progressive disease indicated by these myeloma protein findings. Non-IgM MGUS
Non-IgM MGUS, commonly termed MGUS, is diagnosed in individuals who exhibit a serum IgG, IgD, IgA, or IgE monoclonal protein with or without increased levels of blood and/or urine free κ or λ light chains. These patients typically also show small increases in bone marrow plasma cells. Further requirements for the diagnosis of non-IgM MGUS are: a) bone marrow clonal plasma cells <10% of total nucleated cells; b) absence of any of the four CRAB criteria (CRAB criteria are C = Calcium serum levels >1 milligram/deciliter above normal values and/or a serum level >11 milligram/deciliter; R = Renal insufficiency as defined by a glomerular filtration rate <40 milliliter/minute and/or a serum creatinine >2 gram/deciliter due to myeloma protein-induced kidney damaged; A = Anemia, as defined by a  blood hemoglobin level >2 gram/deciliter below normal and/or <10 gram/deciliter due to the plasma cell dyscrasia rather than e.g. iron deficiency or blood loss; B = Bone lesions, i.e. ≥1 lytic (i.e. bone re-adsorbing) bone lesion due to a plasmacytoma as detected by skeletal radiography, computed tomography, or positron emission tomography-computed tomography); c) no evidence of a plasmacytoma in bone or soft tissues, of amyloidosis, or of another plasma cell disorder; d) a ratio of free serum light chains (i.e.