A 55-year-old woman is found to have clonal plasma cells comprising 8% of bone marrow cellularity, serum M-protein of 2.8 g/dL (IgG kappa), and free light chain (FLC) ratio of 120 (kappa/lambda). There is no anemia, hypercalcemia, renal failure, or lytic bone lesions. Which is the most accurate diagnosis and next management step?
- A MGUS — observe; annual monitoring
- B Smouldering multiple myeloma (SMM) — stratify risk and consider early treatment in ultra-high-risk patients
- C Active multiple myeloma (SLiM-CRAB criteria) — initiate systemic therapy immediately ✓
- D Solitary plasmacytoma — localised radiotherapy
Correct answer: C. Active multiple myeloma (SLiM-CRAB criteria) — initiate systemic therapy immediately
Explanation
The IMWG 2014/updated SLiM criteria added 'biomarker' criteria for active myeloma even without CRAB features. The three SLiM criteria are: (S) >60% clonal plasma cells, (Li) FLC ratio ≥100 (involved/uninvolved), or (M) >1 focal lesion on MRI. This patient's FLC kappa/lambda ratio of 120 (>100) satisfies the 'Li' criterion, thus meeting the definition of active myeloma requiring immediate treatment despite absent classic CRAB findings. Plasma cells at 8% and M-protein 2.8 g/dL alone would have qualified as SMM, but the FLC ratio >100 overrides that classification.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.