A 64-year-old man is found incidentally to have an IgG kappa paraprotein of 25 g/L on routine electrophoresis. He is asymptomatic. Bone marrow biopsy shows 45% clonal plasma cells. Haemoglobin is 12.5 g/dL, calcium 9.4 mg/dL, creatinine 1.0 mg/dL, and skeletal survey shows no lytic lesions. What is the correct diagnosis?
- A Monoclonal gammopathy of undetermined significance
- B Smouldering multiple myeloma ✓
- C Symptomatic multiple myeloma requiring immediate therapy
- D Solitary plasmacytoma
Correct answer: B. Smouldering multiple myeloma
Explanation
Smouldering myeloma requires serum M-protein of at least 30 g/L or clonal marrow plasma cells of 10% or more, without any CRAB features or myeloma-defining events. This patient meets the marrow criterion with 45% plasma cells but lacks end-organ damage, so he has smouldering disease. MGUS requires an M-protein below 30 g/L and fewer than 10% marrow plasma cells, which excludes option A.
Reference: Williams Hematology, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.