Multiple Myeloma

Caused by malignant proliferation of plasma cells producing monoclonal immunoglobulin (M protein) that usually affects older adults (~60-70 years). This causes bone marrow infiltration and osteolytic bone lesions.

Clinical Features (CRAB)

• C: HyperCalcemia → confusion, constipation, polyuria
• R: Renal failure (due to light chain cast nephropathy)
• A: Anemia (normocytic, normochromic)
• B: Bone pain (especially back/ribs), lytic "punched-out" lesions, pathologic fractures

Other features: fatigue, infections (due to immunosuppression)

Diagnosis

• Serum/urine protein electrophoresis (SPEP/UPEP):
  • Monoclonal spike (M protein), usually IgG or IgA
• Serum free light chain assay
• Bone marrow biopsy: >10% clonal plasma cells
• Skeletal survey: multiple punched-out lytic lesions
• Lab abnormalities:
  • ↑ Calcium, ↑ Creatinine, anemia
  • Rouleaux formation on peripheral smear
    • When red blood cells (RBCs) stack together, resembling a pile of coins due to the increased fibrinogen and immunoglobulins, which coat the negatively charged RBCs, diminishing their surface charge. This allows the RBCs to adhere together.
  • Urinalysis
    • Proteinuria
      • Bence Jones proteins
    • Possible granular casts or light chain casts
    • Nephrotic disease
      • Oval fat bodies

Treatment

• Initial:
  • Chemotherapy + corticosteroids (e.g. lenalidomide, bortezomib, dexamethasone)
• Stem cell transplant for eligible patients
• Supportive:
  • Bisphosphonates for bone disease
  • Hydration and avoid nephrotoxic drugs (protect kidneys)
  • Treat hypercalcemia (IV fluids, bisphosphonates)

Complications

• Pathologic fractures, spinal cord compression
• Renal failure
• Infections (due to decreased normal immunoglobulins)
• Amyloidosis

• Older patient with bone pain, anemia, hypercalcemia, renal failure
• Labs show M spike and lytic bone lesions
• Rouleaux formation on blood smear