A 72-year-old man presents with back pain, fatigue, and hypercalcemia. Serum protein electrophoresis shows an M-spike of 4.2 g/dL (IgG kappa). Bone marrow biopsy reveals 35% plasma cells. Serum creatinine is 2.1 mg/dL. X-rays show lytic lesions in the skull and vertebral bodies. Which criteria best establishes the diagnosis of multiple myeloma requiring therapy (symptomatic myeloma)?

• A Serum M-protein > 3 g/dL alone
• B Bone marrow plasma cells > 10% alone
• C CRAB criteria: hypercalcemia, renal failure, anemia, or bone lesions ✓
• D Any IgG M-protein detectable on SPEP

Explanation

Symptomatic multiple myeloma requiring treatment is defined by the CRAB criteria: Hypercalcemia (Ca > 11 mg/dL or > 1 mg/dL above ULN), Renal impairment (Cr > 2 mg/dL), Anemia (Hb < 10 g/dL), Bone lesions (lytic lesions or osteoporosis). This patient has hypercalcemia, renal failure, and bone disease, meeting multiple CRAB criteria. Additional biomarkers of malignancy (ratio of involved/uninvolved free light chains ≥ 100, clonal BMPC ≥ 60%) now also trigger treatment.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.