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Myeloma Cast Nephropathy

  • Mutliple myeloma – Malignant proliferation of plasma cells in BM with prod of Ig
    • Ig light chains (AKA abnormal paraproteins) → BJ proteins → toxic to tubular system
  • Light chains are filtered at glomeruli and appear as BJ proteins

Pathogenesis

  • Kidney damage caused by
    • Hypercalcemia
    • Light chain cast/myeloma cast nephropathy
      • Large tubular casts in urine sediment (IgG light chain + Tamm-Horsfall (THP))
      • The abnormal proteins (Ig) bind with THP → form large tubular casts which are too big to pass → blockage → kidney disease
    • Hyperuricemia
    • Infection, amyloidosis
    • Monoclonal Ig deposition disease
      • Deposits of Ig in kidneys, heart, brain, liver
      • Mostly light chain – cause nodular glomerulosclerosis, similar to DM nephropathy

Clinical features

  • Fatigue, fever, night sweats
  • WL, anaemia
  • Myeloma nephritis – BJ proteinuria
    • Tubular pathology signs – decreased ability to concentrate urine, tubular acidosis
    • Fanconi syndrome – inadequate reabsorption in proximal renal tubule
    • Hypercalemia, hypercalcuria, hyperphosphaturia (hypophosphatemia), glycosuria
  • 3 clinical forms of MN
    • ARF, CRF, Fanconi syndrome (proximal tubule acidosis)

Diagnosis

  • Bone scans, BJ proteins

Treatment

  • ↑fluids to increase diuresis
  • Dialysis DOES NOT improve results – do not give furosemide as it promotes cast formation
  • Transplantation
  • Treat hypercalcemia
  • Allopurinol [300-600mg]

End organ damage CRAB

 

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