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Alport Syndrome

A genetic kidney disease caused by mutations in collagen genes — damaging kidney filters, hearing, and vision. Early treatment can significantly slow progression.

What it is

Mutations in the COL4A3, COL4A4, or COL4A5 genes prevent the body from making normal type IV collagen — a structural protein that forms the glomerular basement membrane (the kidney's main filtration layer). Without it, the membrane weakens and leaks blood and protein into the urine, leading to progressive kidney damage.

Inheritance patterns

About 80% of cases are X-linked (COL4A5 mutation) — inherited through the X chromosome from the mother. Males are usually more severely affected; females may have mild disease or, in some cases, significant kidney disease. The remaining 20% follow autosomal patterns (COL4A3/COL4A4), where one or two copies of a mutation cause disease. Genetic testing clarifies which type a family has.

How common

Approximately 1 in 50,000 live births, though milder autosomal dominant forms (formerly called thin basement membrane nephropathy) are more common than previously recognised. Alport syndrome accounts for roughly 1–2% of all kidney failure cases and 3% in children.

Symptoms to watch

Persistent microscopic hematuria (blood only visible under a microscope) is often the first and earliest sign — sometimes found on a routine school urine test. As disease progresses: protein in urine, rising blood pressure, sensorineural hearing loss (high-frequency first), and eye changes including anterior lenticonus (a specific bulging of the eye lens).

Diagnosis

Genetic testing (blood test) is now the preferred first step — it identifies the specific mutation, confirms the diagnosis, and guides family testing. A kidney biopsy can also diagnose Alport syndrome by showing characteristic GBM changes on electron microscopy (thinning, thickening, and splitting). Hearing tests and an eye exam complete the assessment.

Treatment & slowing progression

ACE inhibitors or ARBs are the cornerstone of treatment — and current guidelines recommend starting them early, even in children with only hematuria and no proteinuria, as they slow GBM damage. SGLT2 inhibitors provide additional kidney protection. Hearing aids help with cochlear hearing loss. Kidney transplant for end-stage disease has excellent outcomes — donor kidneys carry normal collagen.

Alport Syndrome

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Related family guides

Tools and resources for families navigating an Alport Syndrome diagnosis.

Family Resource

Questions to Ask Your Nephrologist

A checklist covering diagnosis, labs, treatment options, and school — especially useful after a new genetic diagnosis.

Read guide → Symptom Guide

Protein in Urine

What proteinuria means in kidney disease and how it's measured — an important marker to track in Alport syndrome.

Read guide → Visual Tool

Kidney Bean eGFR Calculator

Estimate kidney function from creatinine levels — useful for tracking how well the kidneys are working over time.

Use tool → Research

Clinical Trials

Alport syndrome is one of the most active areas of kidney research. See current trials recruiting patients.

Browse trials →

Frequently asked questions

Is Alport syndrome always inherited from a parent?

Usually, but not always. Most cases run in families — either X-linked (a COL4A5 mutation on the X chromosome, typically passed from mother to son) or autosomal (COL4A3 or COL4A4 mutations from one or both parents). Occasionally, Alport syndrome arises from a new mutation with no family history. Genetic testing of parents clarifies the inheritance pattern and identifies other family members who should be tested.

Why does Alport syndrome affect hearing?

Type IV collagen is not only essential in the kidney's filtration membrane but also in the structure of the cochlea — the spiral organ of hearing in the inner ear. When the collagen is abnormal, the sensory hair cells in the cochlea gradually deteriorate, causing sensorineural hearing loss that typically begins with high-frequency sounds. Hearing aids can help significantly and should be fitted as soon as hearing loss is detected.

Do all males with X-linked Alport syndrome reach kidney failure?

Without treatment, about 50% of males with X-linked Alport syndrome develop kidney failure by age 25 and 90% by age 40. With early ACE inhibitor therapy started in childhood — before proteinuria is even present — progression can be delayed by years. SGLT2 inhibitors and newer agents in clinical trials are adding further options. Females with X-linked Alport are usually less severely affected but still need regular monitoring.

Are there new treatments for Alport syndrome?

Early ACE inhibitor treatment is now the strongest evidence-based intervention, and starting it in childhood before proteinuria appears matters. SGLT2 inhibitors (such as empagliflozin and dapagliflozin) are increasingly added for extra kidney protection. Gene therapy, collagen-targeting approaches, and other molecular therapies are in early-stage clinical research. The field is moving quickly — Alport syndrome is one of the most active areas in nephrology research.

Should other family members be tested?

Yes — this is important. First-degree relatives (parents, siblings, and children of affected individuals) should be evaluated with a urine test for blood and protein, kidney function blood tests, hearing assessment, and an eye exam. Genetic testing of the family can identify carriers and at-risk members who benefit from early monitoring and treatment — even before any symptoms appear.

Can people with Alport syndrome receive a kidney transplant?

Yes, and outcomes are generally excellent. A donor kidney carries normal type IV collagen, so it functions properly. Transplant teams monitor for a rare complication called anti-GBM nephritis, where the immune system can react to the normal collagen in the new kidney — but this affects only a small minority of Alport patients. Overall, Alport syndrome patients do very well after transplant.