A 70-year-old man has monoclonal IgG kappa in serum, 8% plasma cells in bone marrow, serum M-protein 2.8 g/dL, no end-organ damage (CRAB criteria absent). This is best classified as:

• A MGUS (monoclonal gammopathy of undetermined significance)
• B Smoldering multiple myeloma ✓
• C Active multiple myeloma
• D Waldenstrom macroglobulinemia

Explanation

Smoldering multiple myeloma is defined by serum M-protein ≥3 g/dL OR bone marrow plasma cells 10-60%, without CRAB criteria (hyperCalcemia, Renal insufficiency, Anemia, Bone lesions). This patient has 8% plasma cells and M-protein 2.8 g/dL — borderline; the plasma cell percentage of 10% is the cutoff, so 8% with M-protein 2.8 and no CRAB fits MGUS. However, M-protein ≥3 g/dL alone qualifies for SMM — this patient at 2.8 g/dL with 8% plasma cells satisfies MGUS criteria. MGUS: M-protein <3 g/dL AND plasma cells <10% AND no CRAB; this case fits MGUS.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.