Kidney amyloidosis differential diagnosis and treatment

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amyloidosis AND kidney

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renal amyloidosis diagnosis typing treatment consensus guideline AL AA ATTR

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https://ashpublications.org/blood/article/120/16/3206/30724/…

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AL amyloidosis AND treatment

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AA amyloidosis AND treatment

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PMID: 38920149

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International Society of Amyloidosis renal amyloidosis diagnosis typing mass spectrometry guidelines

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Kidney amyloidosis: differential diagnosis and treatment

Renal amyloidosis is extracellular deposition of misfolded fibrillar protein in the kidney. It commonly presents with albumin-predominant proteinuria, often nephrotic syndrome, edema, progressive chronic kidney disease, and sometimes renal vein thrombosis. The central rule is:

Confirm amyloid on tissue, then identify the exact amyloid protein before choosing treatment.

Congo-red-positive deposits with apple-green birefringence support amyloid; typing with immunohistochemistry and preferably laser microdissection plus mass spectrometry directs therapy.

Differential diagnosis

1. Types of amyloidosis affecting the kidney

Type	Key clinical associations	Typical renal pattern	Primary treatment
AL amyloidosis	Monoclonal plasma-cell disorder, MGUS, myeloma clone; cardiac failure, neuropathy, hepatomegaly, macroglossia may occur	Very common cause of nephrotic proteinuria and declining eGFR	Plasma-cell directed therapy
AA amyloidosis	Chronic inflammation or infection: rheumatoid arthritis, spondyloarthritis, inflammatory bowel disease, chronic infections, familial Mediterranean fever	Usually glomerular, heavy proteinuria, progressive CKD	Suppress the inflammatory driver and lower serum amyloid A
ALECT2 amyloidosis	Often older adults; certain ethnic backgrounds; may be incidental or present as CKD with modest proteinuria	Predominantly interstitial/vascular disease, CKD more prominent than nephrotic syndrome	Supportive care; no established fibril-directed therapy
Hereditary amyloidosis	Family history, neuropathy/cardiomyopathy, early onset, unexplained CKD; variants in fibrinogen Aα, apolipoprotein AI/AII/CIII, lysozyme, transthyretin, gelsolin, etc.	Fibrinogen Aα often causes severe glomerular renal disease; other forms vary	Gene-specific and type-specific care; genetic counselling
ATTR amyloidosis	Cardiomyopathy and neuropathy predominate; kidney involvement less prominent	Usually mild renal involvement	TTR stabilizer or gene-silencing treatment, guided by amyloid center
Dialysis-associated beta-2 microglobulin amyloidosis	Long-term dialysis; carpal tunnel syndrome, bone/joint disease	Renal presentation is not typical once dialysis-dependent	High-flux dialysis, transplant when appropriate
Localized renal/urinary tract amyloid	May cause hematuria or mass-like lesions, with no systemic syndrome	Localized deposits in renal pelvis, ureter, bladder, or rarely renal parenchyma	Local management and systemic evaluation

AL is the most common systemic form in many renal biopsy series. AA remains particularly important where chronic inflammatory disease, autoinflammatory syndromes, or chronic infection are prevalent. Textbook material notes that AA deposits characteristically affect the kidneys and may lead to progressive proteinuric kidney failure.

2. Conditions that mimic renal amyloidosis

These may cause nephrotic proteinuria and/or similar biopsy appearances:

Diabetic kidney disease
Membranous nephropathy, including PLA2R-associated disease
Focal segmental glomerulosclerosis
Minimal-change disease
Lupus nephritis
Monoclonal gammopathy of renal significance (MGRS), especially:
- Light-chain deposition disease, which is generally Congo-red negative
- Light-chain proximal tubulopathy
- Proliferative glomerulonephritis with monoclonal immunoglobulin deposits
- Cryoglobulinemic glomerulonephritis
Fibrillary glomerulonephritis and immunotactoid glomerulopathy
Collagenofibrotic glomerulopathy
Hypertensive/vascular kidney disease, particularly when proteinuria is not heavy
Other protein-deposition diseases, including monoclonal immunoglobulin deposition diseases

A monoclonal protein alone does not establish AL amyloidosis. MGUS is common in older people and can coexist with hereditary, AA, or ATTR amyloidosis. Tissue typing is therefore mandatory before chemotherapy.

Diagnostic approach

A. Establish renal involvement

Obtain:

Serum creatinine/eGFR, electrolytes, albumin, liver profile
Urinalysis and urine sediment
Urine albumin-creatinine ratio or 24-hour urine protein
Lipid profile if nephrotic syndrome
Assessment for edema, orthostatic symptoms, thrombosis, and infection risk

B. Confirm amyloid histologically

Kidney biopsy provides the most direct assessment when kidney involvement is suspected and biopsy risk is acceptable.
Congo red stain shows characteristic birefringence under polarized light.
Electron microscopy can demonstrate nonbranching fibrils.
Less invasive sampling, such as abdominal fat-pad aspirate, bone marrow, or involved tissue, may diagnose systemic amyloid, but a negative fat-pad result does not exclude renal AL amyloidosis.

C. Type the amyloid protein

Use mass spectrometry-based proteomics where available. This is preferred because immunohistochemistry may misclassify deposits.

D. Determine the cause after typing

If AL suspected

Serum immunofixation
Urine immunofixation
Serum free light-chain assay
Bone-marrow examination with clonal plasma-cell assessment
Evaluate cardiac involvement promptly: NT-proBNP/troponin, ECG, echocardiography, and cardiac MRI or specialized nuclear imaging when indicated

If AA suspected

CRP, ESR, serum amyloid A where available
Search for chronic inflammatory, infectious, autoimmune, or autoinflammatory disease
Consider familial Mediterranean fever or other periodic-fever syndromes based on ancestry, symptoms, and age of onset

If hereditary amyloid suspected

Germline genetic testing after protein typing or when phenotype strongly suggests it
Family counselling and evaluation

Treatment

1. General kidney and nephrotic-syndrome management

These measures apply alongside disease-specific treatment:

Restrict dietary sodium and use loop diuretics for edema, cautiously because intravascular depletion and hypotension can occur.
Use ACE inhibitor or ARB for proteinuria when blood pressure, potassium, and kidney function allow.
Consider an SGLT2 inhibitor for proteinuric CKD when clinically appropriate, although individual tolerance and eGFR thresholds matter.
Manage blood pressure, lipids, diabetes, and cardiovascular risk.
Vaccinate and assess infection risk, especially before immunosuppression.
Assess thrombosis risk in severe nephrotic syndrome. Anticoagulation is individualized because bleeding risk, albumin level, kidney function, and planned biopsy/procedures matter.
Avoid nephrotoxins, including NSAIDs and unnecessary iodinated contrast.
Plan kidney replacement therapy if progressive kidney failure occurs.
Kidney transplantation can be appropriate when the underlying precursor production is controlled. Recurrence risk depends on amyloid type and control of the causative disease.

2. AL amyloidosis

AL is a hematologic emergency when significant cardiac, renal, neurologic, or autonomic involvement exists. Refer early to a center experienced in amyloidosis, hematology, nephrology, and cardiology.

Disease-directed therapy

Current first-line therapy commonly uses daratumumab plus cyclophosphamide, bortezomib, and dexamethasone in eligible patients.
Some patients receive bortezomib-based therapy without daratumumab depending on access, frailty, contraindications, or local protocols.
Autologous stem-cell transplantation can provide durable responses in carefully selected, lower-risk patients.
Relapsed/refractory disease may need additional plasma-cell targeted regimens, selected by prior therapy, organ function, cytogenetics, and response.

The goal is rapid, deep reduction of the toxic monoclonal free light chain, because this offers the best chance of stabilizing or improving organ function. A 2023 consensus guideline supports prompt bortezomib-cyclophosphamide-dexamethasone-based induction with or without daratumumab and close multidisciplinary organ support (Tan et al., 2023, PMID 38920149).

Important: Do not give AL chemotherapy unless the amyloid type is established or there is compelling expert-level evidence of a pathogenic plasma-cell clone.

3. AA amyloidosis

The treatment is sustained control of the disease driving serum amyloid A production.

Examples:

Rheumatoid arthritis, spondyloarthritis, inflammatory bowel disease: effective disease-modifying treatment, often biologic therapy where indicated.
Familial Mediterranean fever: colchicine is foundational; IL-1 inhibition is used for inadequate control or colchicine resistance/intolerance.
Chronic infection: definitive antimicrobial and source-control treatment.
Autoinflammatory syndromes: targeted cytokine inhibition, often IL-1 pathway treatment when appropriate.

Renal outcomes correlate with suppression of inflammation and serum amyloid A. Dialysis and transplantation may be needed in advanced kidney failure, but ongoing inflammation must remain controlled to reduce graft recurrence.

4. Hereditary renal amyloidosis

Management depends on the protein:

Fibrinogen Aα-chain amyloidosis: may progress rapidly to kidney failure. Kidney transplant can be considered; recurrence is possible because the liver produces the mutant fibrinogen. Combined liver-kidney transplantation is reserved for selected situations and specialist assessment.
Apolipoprotein and lysozyme variants: supportive renal care, transplantation in advanced disease, plus genetic counselling.
ATTR: kidney disease is usually not the central problem. TTR-directed therapy is selected based on neuropathy/cardiomyopathy phenotype.
All hereditary cases should receive genetic counselling and appropriate family testing.

5. ALECT2 amyloidosis

There is no established treatment that removes or stops ALECT2 deposits. Care is supportive:

Blood-pressure and proteinuria control
CKD complication management
Dialysis or kidney transplantation when needed

When to refer urgently

Prompt nephrology and hematology evaluation is warranted for:

Nephrotic syndrome or rapidly rising proteinuria
Rapid eGFR decline or acute kidney injury
A monoclonal protein plus otherwise unexplained proteinuria, edema, cardiomyopathy, neuropathy, hepatomegaly, or autonomic dysfunction
Suspected cardiac amyloidosis: dyspnea, syncope, hypotension, arrhythmia, high troponin/NT-proBNP
Suspected hereditary disease or a family history of renal failure/amyloidosis

This is educational information, not a substitute for individualized care. The practical next step in a suspected case is usually nephrology referral for tissue confirmation and definitive amyloid typing before committing to disease-specific treatment.

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