Alport syndrome and Alport kidney diseases - elucidating the disease spectrum.

PURPOSE OF REVIEW: With the latest classification, variants in three collagen IV genes, COL4A3 , COL4A4 , and COL4A5 , represent the most prevalent genetic kidney disease in humans, exhibiting diverse, complex, and inconsistent clinical manifestations. This review breaks down the disease spectrum and genotype-phenotype correlations of kidney diseases linked to genetic variants in these genes and distinguishes "classic" Alport syndrome (AS) from the less severe nonsyndromic genetically related nephropathies that we suggest be called "Alport kidney diseases". RECENT FINDINGS: Several research studies have focused on the genotype-phenotype correlation under the latest classification scheme of AS. The historic diagnoses of "benign familial hematuria" and "thin basement membrane nephropathy" linked to heterozygous variants in COL4A3 or COL4A4 are suggested to be obsolete, but instead classified as autosomal AS by recent expert consensus due to a significant risk of disease progression. SUMMARY: The concept of Alport kidney disease extends beyond classic AS. Patients carrying pathogenic variants in any one of the COL4A3/A4/A5 genes can have variable phenotypes ranging from completely normal/clinically unrecognizable, hematuria without or with proteinuria, or progression to chronic kidney disease and kidney failure, depending on sex, genotype, and interplays of other genetic as well as environmental factors.

Is there a dominant-negative effect in individuals with heterozygous disease-causing variants in COL4A3/COL4A4?

Alport syndrome (AS) shows a broad phenotypic spectrum ranging from isolated microscopic hematuria (MH) to end-stage kidney disease (ESKD). Monoallelic disease-causing variants in COL4A3/COL4A4 have been associated with autosomal dominant AS (ADAS) and biallelic variants with autosomal recessive AS (ARAS). The aim of this study was to analyze clinical and genetic data regarding a possible genotype-phenotype correlation in individuals with disease-causing variants in COL4A3/COL4A4. Eighty-nine individuals carrying at least one COL4A3/COL4A4 variant classified as (likely) pathogenic according to the American College of Medical Genetics guidelines and current amendments were recruited. Clinical data concerning the prevalence and age of first reported manifestation of MH, proteinuria, ESKD, and extrarenal manifestations were collected. Individuals with monoallelic non-truncating variants reported a significantly higher prevalence and earlier diagnosis of MH and proteinuria than individuals with monoallelic truncating variants. Individuals with biallelic variants were more severely affected than those with monoallelic variants. Those with biallelic truncating variants were more severely affected than those with compound heterozygous non-truncating/truncating variants or individuals with biallelic non-truncating variants. In this study an association of heterozygous non-truncating COL4A3/COL4A4 variants with a more severe phenotype in comparison to truncating variants could be shown indicating a potential dominant-negative effect as an explanation for this observation. The results for individuals with ARAS support the, still scarce, data in the literature.

Whole exome sequencing approach for identification of the molecular etiology in pediatric patients with hematuria.

BACKGROUND: Hematuria is a common condition in clinical practice of pediatric patients. It is related to a wide spectrum of disorders and has high heterogeneity both clinically and genetically, which contributes to challenges of diagnosis and lead many pediatric patients with hematuria not to receive accurate diagnosis and early management. METHODS: In this single center study, 42 children with hematuria were included in Tianjin Children's Hospital between 2019 and 2020. We analyzed the clinical information and performed WES (Whole exome sequencing) for all cases. Then the classification of identified variants was performed according to the American College of Medical Genetics and Genomics (ACMG) guidelines for interpreting sequence variants. For the fragment deletion, qPCR was performed to validate and confirm the inherited pattern. RESULTS: For the 42 patients, 16 cases had gross hematuria and 26 had microscopic hematuria. Molecular genetic causes were uncovered in 9 (21.4%) children, including 7 with Alport syndrome (AS), one with polycystic nephropathy and one with lipoprotein glomerulopathy. The genetic causes for other patients were not related with hematuria. CONCLUSIONS: WES is a rapid and effective way to evaluate patients with hematuria. The analysis of genotype-phenotype correlations of patients with AS indicated that severe variants were associated with early kidney failure. Secondary findings were not rare in Chinese children, thus the clinician should pay more attention to the clinical interpretation of sequencing results and properly interaction with patients and their family.

EarlyTect BCD, a Streamlined PENK Methylation Test in Urine DNA, Effectively Detects Bladder Cancer in Patients with Hematuria.

The current noninvasive diagnostic approaches for detecting bladder cancer (BC) often exhibit limited clinical performance, especially for the initial diagnosis. This study aims to evaluate the validity of a streamlined urine-based PENK methylation test called EarlyTect BCD in detecting BC in patients with hematuria scheduled for cystoscopy in Korean and American populations. The test seamlessly integrates two steps, linear target enrichment and quantitative methylation-specific PCR within a single closed tube. The detection limitation of the test was approximately two genome copies of methylated PENK per milliliter of urine. In the retrospective training set (n = 105), an optimal cutoff value was determined to distinguish BC from non-BC, resulting in a sensitivity of 87.3% and a specificity of 95.2%. In the prospective validation set (n = 210, 122 Korean and 88 American patients), the overall sensitivity for detecting all stages of BC was 81.0%, with a specificity of 91.5% and an area under the curve value of 0.889. There was no significant difference between the two groups. The test achieved a sensitivity of 100% in detecting high-grade Ta and higher stages of BC. The negative predictive value of the test was 97.7%, and the positive predictive value was 51.5%. The findings of this study demonstrate that EarlyTect BCD is a highly effective noninvasive diagnostic tool for identifying BC among patients with hematuria.

La nefropatía del colágeno IV (3-4) / Collagen IV (3-4) nephropathy

Se ha demostrado que los genes COL4A3, COL4A4 y COL4A5 están implicadosen distintas manifestaciones renales. Mutaciones en estos genes del colágenoIV afectan la estructura de la membrana basal glomerular (MBG) dando lugar auna nefropatía cuyos síntomas oscilan desde la hematuria aislada hasta la insuficienciarenal. Estas alteraciones renales han sido consideradas históricamente comodistintas entidades: síndrome de Alport autosómico dominante, hematuria familiarbenigna y portadores del síndrome de Alport autosómico recesivo. Pero el conocimientomolecular de estas enfermedades ha hecho que podamos agruparlas bajoel epígrafe de «nefropatía del colágeno IV». Este hecho tiene importantes implicacionesen el diagnóstico, pronóstico y seguimiento de la enfermedad

Recent evidence has shown that the COL4A3, COL4A4 and COL4A5 genes areinvolved in different renal manifestations. Mutations in these collagen type IV genesaffect the glomerular basement membrane (GBM) giving rise to a nephropathywhose symptoms range from isolated hematuria to severe renal failure. This disorderhas been traditionally considered to be different entities: Autosomal DominantAlport syndrome, Familial Benign Hematuria, Autosomal Recessive Alport Syndromecarriers. But the increased knowledge of the molecular basis of this clinicaldiversity prompted us to agglutinate these entities under the name of «collagentype IV nephropathy». This fact has relevant implications in diagnosis, prognosisand management

Hematuria Familiar Benigna / No disponible

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