A 58-year-old asymptomatic man is found to have 20% clonal bone marrow plasma cells, an IgG kappa M-protein of 2.8 g/dL, hemoglobin 12.5 g/dL, normal calcium, creatinine 0.9 mg/dL, and no lytic lesions on skeletal survey. What is the correct diagnosis and management implication?
- A MGUS; observation only
- B Active multiple myeloma; immediate induction chemotherapy
- C Smoldering multiple myeloma; observation with monitoring ✓
- D Solitary plasmacytoma; local radiotherapy
Correct answer: C. Smoldering multiple myeloma; observation with monitoring
Explanation
Smoldering myeloma is defined by serum M-protein of 3 g/dL or more, or clonal plasma cells of 10% or more, without CRAB features or myeloma-defining biomarkers. This patient meets the plasma cell criterion with no end-organ damage, so treatment is deferred with regular monitoring. MGUS requires plasma cells below 10% and M-protein below 3 g/dL. Active myeloma requires a CRAB feature or a myeloma-defining event such as free light chain ratio of 100 or more.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.