A 68-year-old man presents with bone pain, anemia, renal failure, and a serum protein spike. Bone marrow biopsy shows 40% plasma cells. Serum immunofixation reveals IgG kappa paraprotein. Which feature, if present, would MOST reliably distinguish symptomatic multiple myeloma requiring treatment from smoldering myeloma?
- A End-organ damage (CRAB criteria) — hypercalcemia, renal failure, anemia, or bone lesions ✓
- B Serum M-protein level above 3 g/dL
- C Bone marrow plasma cells exceeding 10%
- D Elevated serum free light chain ratio above 8
Correct answer: A. End-organ damage (CRAB criteria) — hypercalcemia, renal failure, anemia, or bone lesions
Explanation
The CRAB criteria (hyperCalcemia, Renal insufficiency, Anemia, Bone lesions) define end-organ damage and distinguish symptomatic multiple myeloma requiring immediate treatment from smoldering myeloma. Smoldering myeloma may have >10% plasma cells and M-protein >3 g/dL but lacks CRAB features. A free light chain ratio >100 is one of the SLiM criteria added to indicate ultra-high risk smoldering myeloma now also warranting treatment.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.