Cast nephropathy
Cast nephropathy (myeloma kidney) is acute or subacute kidney injury caused by intratubular obstruction from free light chain and Tamm-Horsfall protein casts, occurring almost exclusively in multiple myeloma with markedly elevated serum free light chains. Treatment is emergency chemotherapy to rapidly lower free light chain production, combined with aggressive isotonic hydration and avoidance of nephrotoxins.
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What this article covers
- Overview
Cast nephropathy (myeloma kidney) is acute or subacute kidney injury caused by intratubular obstruction, occurring when markedly elevated concentrations of monoclonal free light chains are freely…
- Epidemiology
Nearly 50% of all patients with multiple myeloma develop kidney disease, most commonly acute kidney injury (AKI) caused by cast nephropathy, frequently the presenting feature that leads to the myeloma diagnosis.
- Risk factors
Multiple myeloma with a markedly elevated serum free light chain burden, the prerequisite for cast formation; the risk rises with the absolute free light chain concentration.
- Pathophysiology
Free light chains are freely filtered at the glomerulus because of their small molecular size, then reach high concentrations in the distal nephron.
- Clinical features
Acute or slowly progressive kidney injury in a patient with known or newly suspected multiple myeloma is the hallmark presentation, often precipitated by dehydration, NSAID use, loop diuretics, or contrast exposure.
- Differential diagnosis
Acute tubular necrosis: from ischemia, sepsis, or nephrotoxins, lacks the markedly elevated serum free light chains and cast morphology of myeloma kidney, though it can coexist as a precipitant in a myeloma patient.
- Diagnosis
The diagnosis is confirmed by kidney biopsy showing fractured, angulated intratubular casts surrounded by a multinucleated giant cell reaction, in a patient with markedly elevated serum free light…
- Management
First, initiate hydration with isotonic (normal saline) IV fluids to correct volume depletion and increase tubular flow, which reduces intratubular light chain concentration and helps prevent further…
- Complications
Progression to dialysis-dependent kidney failure, which can become irreversible if chemotherapy and light chain reduction are delayed.
- Prognosis
Kidney recovery is closely tied to the speed and depth of free light chain reduction: rapid lowering of free light chains with bortezomib-based chemotherapy correlates with kidney recovery and…
- Prevention
In any patient with known multiple myeloma, avoid NSAIDs entirely, given the risk of precipitating cast nephropathy even with a previously normal creatinine.
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