A 55-year-old man with plasma cell myeloma has a serum free light chain ratio of 110 (kappa/lambda). Which of the following CRAB criteria does he still need to establish before diagnosing symptomatic myeloma if no other features are present?

• A He must demonstrate at least one of: hypercalcemia, renal failure, anemia, or lytic bone lesions
• B A monoclonal protein >3 g/dL in serum by itself establishes diagnosis
• C CRAB criteria have been replaced entirely by PET-CT findings
• D Bone marrow plasma cells ≥10% is sufficient; CRAB features are not required if biomarkers of malignancy are present ✓

Explanation

Per current IMWG (2014) criteria, a serum free light chain ratio ≥100 (involved/uninvolved) constitutes a SLiM biomarker of malignancy. When combined with ≥10% clonal bone marrow plasma cells, this alone qualifies as symptomatic myeloma requiring treatment, even without CRAB organ damage. CRAB features remain valid alternative pathways but are no longer mandatory when SLiM criteria are fulfilled. This paradigm shift allows earlier treatment before end-organ damage.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.