Collagen type IV-related nephropathies in Portugal: pathogenic COL4A5 mutations...

• Author(s): Sá, MJ ; Storey, H ; Flinter, F ; Nagel, M ; Sampaio, S ; Castro, R ; Araújo, JA ; Gaspar, MA ; Soares, C ; Oliveira, A ; Henriques, AC ; Costa, AG ; Abreu, CP ; Ponce, P ; Alves, R ; Pinho, L ; Silva, SE ; Moura, CP ; Mendonça, L ; Carvalho, F
• Date: 2014
• Persistent ID: http://hdl.handle.net/10400.23/718
• Origin: Repositório Científico do Hospital de Braga
• Subject(s): Colágenio Tipo IV; Doenças do Rim; Portugal
• Document Type: Article
• Language: English

Description

Pathogenic mutations in genes COL4A3/COL4A4 are responsible for autosomal Alport syndrome (AS) and thin basement membrane nephropathy (TBMN). We used Sanger sequencing to analyze all exons and splice site regions of COL4A3/COL4A4, in 40 unrelated Portuguese probands with clinical suspicion of AS/TBMN. To assess genotype-phenotype correlations, we compared clinically relevant phenotypes/outcomes between homozygous/compound heterozygous and apparently heterozygous patients. Seventeen novel and four reportedly pathogenic COL4A3/COL4A4 mutations were identified in 62.5% (25/40) of the probands. Regardless of the mutated gene, all patients with ARAS manifested chronic renal failure (CRF) and hearing loss, whereas a minority of the apparently heterozygous patients had CRF or extrarenal symptoms. CRF was diagnosed at a significantly younger age in patients with ARAS. In our families, the occurrence of COL4A3/COL4A4 mutations was higher, while the prevalence of XLAS was lower than expected. Overall, a pathogenic COL4A3/COL4A4/COL4A5 mutation was identified in >50% of patients with fewer than three of the standard diagnostic criteria of AS. With such a population background, simultaneous next-generation sequencing of all three genes may be recommended as the most expedite approach to diagnose collagen IV-related glomerular basement membrane nephropathies.