The Intern At Work: Internal Medicine 24. Blood is Thicker Than Water- Multiple Myeloma
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Mar 31, 2019 A concise tour of multiple myeloma definitions and how to tell smoldering from active disease. The CRAB mnemonic and how malignant plasma cells cause bone lesions and organ damage are highlighted. Tests and preferred imaging for detecting lytic lesions are covered. Treatment pathways including transplant, maintenance, and supportive care are outlined.
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Definition And Core Diagnostic Criteria
- Multiple myeloma is a malignant plasma cell disorder causing end-organ dysfunction beyond a simple protein spike.
- Diagnosis requires >10% clonal marrow plasma cells or plasmacytoma plus a myeloma-defining event such as CRAB or biomarker thresholds.
Two Categories Of Myeloma Defining Events
- Myeloma-defining events split into CRAB end-organ damage and biomarkers of malignancy.
- Biomarkers include >60% clonal marrow plasma cells, involved/uninvolved free light chain ratio >100, or >1 focal MRI lesion.
Smoldering Myeloma Criteria And Management
- Smoldering myeloma meets numeric thresholds (M protein ≥30 g/L or urinary M >500 mg/24h or marrow clonal cells ≥10%) but lacks end-organ damage.
- Risk of progression is ~10% per year for 5 years and management is observation outside trials.