Synopsis
Recognise renal amyloid and MGRS, prove the deposited protein or lesion, and secure rapid nephrology–haematology treatment of the pathogenic clone.
- Amyloidosis is extracellular deposition of misfolded fibrils; renal AL amyloid commonly causes albumin-predominant proteinuria, nephrotic syndrome and progressive kidney impairment.
- MGRS describes kidney injury caused by a monoclonal immunoglobulin from a B-cell or plasma-cell clone that may be too small to meet conventional malignancy treatment criteria.
- A small paraprotein is not necessarily incidental when renal biopsy demonstrates a compatible monoclonal lesion.
- Use serum and urine immunofixation plus serum free light chains, interpreting the ratio in the context of reduced renal clearance; electrophoresis alone can miss disease.
- Congo-red positivity establishes amyloid, but the fibril protein must be typed because AL, AA, transthyretin and hereditary forms have different treatments.
- Kidney biopsy requires light microscopy, immunofluorescence and electron microscopy; mass-spectrometry typing or expert review is valuable when staining is uncertain.
- AL amyloidosis is systemic until shown otherwise, so cardiac biomarkers and organ staging are urgent because cardiac involvement strongly shapes tolerance and prognosis.
- Treatment targets the clone or inflammatory precursor rather than the proteinuria alone and should be planned jointly by nephrology, haematology and the relevant specialist service.
Key red flags
Breathlessness, syncope, raised biomarkers, low-voltage ECG or increased ventricular wall thickness may indicate high-risk cardiac involvement.
Abrupt acute kidney injury, hypercalcaemia, anaemia, bone pain or infection requires expedited haematology and nephrology assessment.
Investigation priorities
Detect and characterise a monoclonal immunoglobulin with greater sensitivity than electrophoresis alone.
Management branches
An adult has unexplained proteinuria, CKD, nephrosis or proximal tubular dysfunction.
- Characterise urine albumin and total protein, sediment, renal trajectory and systemic features rather than relying on a dipstick.
- Request serum free light chains plus serum and urine immunofixation and review calcium, blood count and bone symptoms.
- Contact nephrology urgently for rapid functional loss, nephrotic complications or a strong monoclonal signal, adding haematology early when organ injury is likely.
Key medicines
Clone-directed therapy for AL amyloid or MGRSThe haematology–nephrology multidisciplinary team must choose and renal-adjust the current disease-specific regimen; no single bortezomib-, antibody- or chemotherapy schedule applies to all lesions.Cardiac amyloid, autonomic hypotension, neuropathy, cytopenia, infection and renal impairment alter tolerability. Check live NICE access, SmPCs, antiviral or antimicrobial prophylaxis and tumour-lysis planning before treatment.
Loop diuretic for symptomatic oedemaTitrate the locally selected oral or intravenous preparation to congestion, renal response and blood pressure; severe nephrosis or cardiac amyloid often requires specialist-guided adjustment rather than a fixed dose.Daily weight alone cannot distinguish safe decongestion from intravascular depletion. Monitor orthostasis, creatinine, sodium, potassium and magnesium; combine agents only through an agreed plan, especially with restrictive cardiomyopathy.