A 62-year-old asymptomatic woman is found on routine testing to have a serum IgG kappa M-protein of 3.6 g/dL. Bone marrow biopsy shows 15% clonal plasma cells. Hemoglobin is 12.5 g/dL, calcium 9.2 mg/dL, creatinine 0.9 mg/dL, and skeletal survey and whole-body MRI show no lytic lesions. Urine protein electrophoresis shows no monoclonal light chain. What is the most appropriate diagnosis?

• A Monoclonal gammopathy of undetermined significance
• B Smoldering multiple myeloma ✓
• C Solitary plasmacytoma of bone
• D POEMS syndrome

Explanation

Smoldering multiple myeloma requires serum M-protein of at least 3 g/dL or clonal marrow plasma cells of 10 percent or more, in the absence of any myeloma-defining event such as CRAB features or biomarkers of malignancy. This patient meets both thresholds with zero CRAB findings. MGUS requires an M-protein below 3 g/dL and plasma cells below 10 percent, so it is excluded, and plasmacytoma requires a discrete osseous or extraosseous mass.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.