Alport syndrome arises from pathogenic variants in genes encoding type IV collagen chains of the glomerular basement membrane. In XLAS, variants in COL4A5 (located on the X chromosome) disrupt the alpha-5(IV) collagen chain, accounting for the more severe disease course typically documented in males. In ARAS, biallelic pathogenic variants in COL4A3 or COL4A4 are causative. In ADAS, heterozygous pathogenic variants in COL4A3 or COL4A4 cause disease with reduced penetrance; the absolute ESKD risk from a heterozygous variant in these genes is estimated at significantly below 3%, though clinical severity varies widely even within the same family. A digenic form is also documented. Variant type within COL4A5 substantially influences disease trajectory in XLAS: large rearrangements, nonsense variants, and frameshift variants carry the highest risk of early ESKD; splice site variants confer intermediate risk; missense variants are associated with later-onset kidney failure. In XLAS females, both genotype and X-chromosome inactivation patterns can affect disease severity.

Diagnostic criteria for Alport syndrome have been published. Molecular genetic testing is considered in individuals with persistent glomerular hematuria accompanied by one or more of the following: sensorineural deafness; anterior lenticonus and/or characteristic retinopathy; diffuse leiomyomatosis; family history of hematuria, chronic kidney disease, or deafness associated with kidney disease; or characteristic pathologic findings on kidney biopsy. Pathologic findings include negative or nonspecific routine immunofluorescence, abnormal type IV collagen expression, thin GBM, and characteristic GBM thickening, lamellation, and scalloping. Molecular genetic testing identifies pathogenic variants in COL4A5 (X-linked forms) or COL4A3 and COL4A4 (autosomal forms). Evaluations following diagnosis include urine albumin-to-protein excretion measurement, kidney function assessment, hearing evaluation, and ophthalmologic assessment. Ongoing surveillance for microalbuminuria and proteinuria through nephrology follow-up is part of the documented clinical framework. Differential diagnosis includes IgA nephropathy, C3 glomerulopathy, and other collagen IV-related nephropathies.

No FDA-approved treatments are documented in this packet specifically for Alport syndrome. The GeneReviews chapter documents published clinical practice recommendations in which early intervention is directed at suppressing proteinuria. Angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) represent the documented therapeutic approach for kidney disease management; early initiation is associated with delayed ESKD onset in documented clinical guidance. Hypertension management follows standard approaches. Kidney transplantation is a documented management option for individuals reaching ESKD, with specific considerations for selection of living-related kidney donors. Hearing aids are documented for hearing deficits. Eye care is included in the documented framework for individuals with ocular manifestations. The GeneReviews data documents dehydration as a factor associated with worsened manifestations, and loud noise as relevant to hearing outcomes. Protective measures for the corneas are documented for individuals with recurrent corneal erosions.

Prognosis varies substantially by inheritance pattern and variant type. In XLAS males, large rearrangements and nonsense or frameshift variants in COL4A5 confer approximately a 50% probability of ESKD before age 20 years. Splice site variants are associated with a 65% probability of ESKD before age 30, with 50% reaching ESKD by age 25. Missense variants carry lower risk: approximately 30% probability of ESKD before age 30 and 50% by age 40. XLAS females have a milder documented course, with approximately 20% reaching ESKD by age 60. ARAS carries a more severe prognosis: approximately 80% probability of ESKD by age 30. In ADAS, the absolute ESKD risk is estimated significantly below 3%, though individual outcomes vary. Anterior lenticonus and central retinopathy in XLAS males typically indicate kidney failure onset before age 30, and are more commonly observed with COL4A5 deletions or premature stop codon variants.

Fifteen active clinical trials for Alport syndrome are documented in this packet. The GeneReviews chapter references the Alport Syndrome Foundation as a resource for current clinical trial listings. Documented areas of investigation include pharmacologic kidney protection strategies and emerging therapeutic candidates. The well-characterized genotype-phenotype relationships across XLAS, ARAS, ADAS, and digenic forms provide a framework supporting therapeutic development. Information on active studies is accessible through ClinicalTrials.gov and the EU Clinical Trials Register.