Myeloma cast nephropathy can present as unexplained acute kidney injury or a creatinine that keeps rising, especially in older patients with anaemia, hypercalcaemia or bone pain.
Urine dipstick detects albumin, not light chains, so a bland dipstick does not exclude it. Send serum free light chains with the kappa:lambda ratio and serum protein electrophoresis with immunofixation when the cause of kidney injury is unclear.
Very high involved light chains with a markedly abnormal ratio warrant urgent haematology referral; delay costs kidney function.
- Consider myeloma in unexplained AKI, especially with anaemia or hypercalcaemia
- A negative protein dipstick does not exclude light-chain disease
- Send serum free light chains and protein electrophoresis with immunofixation
- Refer urgently when light chains are markedly raised
Why it matters
Renal recovery in cast nephropathy depends on how quickly light chains are lowered.
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