The kidney in plasma cell disorders
- Lesion
Abnormal light chains block tubules, fold into amyloid or coat basement membranes; each pattern gives a different kidney disease.
What it is
A clone of plasma cells can damage the kidney even before it qualifies as myeloma (monoclonal gammopathy of renal significance). Free light chains filtered by the glomerulus bind uromodulin and form obstructing casts; some light chains fold into amyloid fibrils in glomeruli and vessels; others deposit as non-fibrillar material in basement membranes, or injure proximal tubules. Fibrillary glomerulonephritis is a separate disease with randomly arranged fibrils that do not stain with Congo red and carry the marker DNAJB9.
Structure
- Cast nephropathy: pink to blue, glassy, cracked casts in tubules, with multinucleated giant cells and interstitial inflammation.
- Amyloid: acellular eosinophilic material in mesangium, capillary walls and vessels; fibrils of about ten nanometres on EM.
- LCDD: nodules resembling diabetic nodules, with monoclonal light chain along tubular and glomerular membranes.
- Proximal tubulopathy: crystals or inclusions of light chain in proximal cells, causing Fanconi syndrome.
Paraprotein kidney lesions
| Lesion | Where | Main clue | Presentation |
|---|---|---|---|
| Cast nephropathy | Distal tubules | Fractured casts with giant cells | Acute kidney injury |
| AL amyloidosis | Glomeruli, vessels | Congo red, apple-green birefringence | Nephrotic syndrome |
| Light-chain deposition disease | GBM, tubular membranes | Linear monoclonal kappa or lambda | Proteinuria, kidney failure |
| Fibrillary GN | Glomeruli | Congo red negative fibrils, DNAJB9 | Proteinuria, hematuria |
| Light-chain proximal tubulopathy | Proximal tubules | Crystalline inclusions | Fanconi syndrome |
Clinical notes
- Unexplained kidney injury in an older adult with anemia, back pain or high calcium: check serum free light chains and protein electrophoresis.
- Bence Jones protein is not detected by the urine dipstick, which reacts mainly to albumin.
Test yourself
Think of the answer, then tap the question to see it.
Why do light chains form casts in the distal nephron?
Filtered free light chains bind uromodulin (Tamm-Horsfall protein) in the thick ascending limb and distal tubule and precipitate.
How is amyloid confirmed in a kidney biopsy?
With Congo red stain, which shows apple-green birefringence under polarized light, and by fibrils on EM.
How does fibrillary GN differ from amyloid?
Its fibrils are thicker, do not stain with Congo red and the deposits are DNAJB9-positive.
Elsewhere in DurgiPedia
- Intracellular accumulations: cholesterol, proteins, hyaline, glycogen
- Special stains in diagnosis: Congo red, Prussian blue, PAS, Ziehl–Neelsen, Gram
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Multiple myeloma: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.