Abstract
60% clonal plasma cells in the marrow, serum free light chain (FLC) ratio 100 (provided involved FLC level 100), and more than 1 focal lesion ( 5mm in size) on magnetic resonance imaging (MRI) or whole body or spine/pelvis (Table1). Each of these biomarkers has been validated in 2 or more independent studies to have a very high risk (w80%) of progression to symptomatic disease within 2 years. In addition, the update allows modern imaging methods including computed tomography (CT) and positron emission tomography-CT to diagnose MM bone disease. The new diagnostic criteria provide 3 important clarifications on requirements for bone and renal disease in the diagnosis of MM. First, the presence of osteoporosis, vertebral compression fractures, or bone densitometric changes in the absence of lytic lesions is not considered sufficient evidence of myeloma bone disease. Second, only suspected or proven light chain cast nephropathy is considered as meeting the renal component of the CRAB criteria. Renal disorders associated with M proteins such as light chain deposition disease, membranoproliferative glomerulonephritis, and AL amyloidosis, are considered unique diseases and not MM. Third, an estimated GFR less than 40 ml/ minute is preferred to the serum creatinine concentration for purposes of fulfilling the CRAB criteria. Table 1 International Myeloma Working Group Diagnostic Criteria for Smoldering Multiple Myeloma and Multiple Myeloma Disorder Disease Definition Smoldering multiple myeloma Both criteria must be met: Serum monoclonal protein (IgG or IgA) 3gm/dL, or urinary monoclonal protein 500 mg per 24h and/or clonal bone marrow plasma cells 10-60% Absence of myeloma defining events or amyloidosis Multiple Myeloma Both criteria must be met: Clonal bone marrow plasma cells 10% or biopsy-proven bony or extramedullary plasmacytoma Any one or more of the following myeloma defining events (MDE): BCRAB features felt attributable to the underlying plasma cell proliferative disorder, specifically:
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