A 68-year-old man presents with bone pain, serum calcium 11.8 mg/dL, creatinine 2.1 mg/dL, and haemoglobin 8.2 g/dL. Serum protein electrophoresis shows an M-protein of 4.2 g/dL. Bone marrow shows 35% plasma cells. Which WHO criterion is MET to define multiple myeloma over smouldering myeloma?
- A Serum free light chain ratio > 100
- B Bone marrow plasma cells ≥ 10%
- C CRAB criteria: hypercalcaemia (serum calcium > 11 mg/dL) ✓
- D M-protein > 3 g/dL on SPEP
Correct answer: C. CRAB criteria: hypercalcaemia (serum calcium > 11 mg/dL)
Explanation
Active multiple myeloma (requiring treatment) is defined by ≥10% clonal plasma cells PLUS at least one CRAB criterion (hypCalcaemia >11 mg/dL, Renal insufficiency, Anaemia Hb <10g/dL, Bone lesions) or one SLiM criterion (≥60% plasma cells, free light chain ratio ≥100, >1 focal lesion on MRI). This patient has CRAB features confirming active myeloma. Smouldering myeloma lacks CRAB/SLiM criteria despite elevated M-protein and >10% marrow plasma cells. Bone marrow ≥10% alone and M-protein >3 g/dL without CRAB define smouldering disease.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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