Browsing by Author "Tavares, I"
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- Collagen Type IV-Related Nephropathies in Portugal: Pathogenic COL4A5 Mutations and Clinical Characterization of 22 FamiliesPublication . Nabais Sá, MJ; Sampaio, S; Oliveira, A; Alves, S; Moura, CP; Silva, SE; Castro, R; Araújo, JA; Rodrigues, M; Neves, F; Seabra, J; Soares, C; Gaspar, MA; Tavares, I; Freitas, L; Sousa, TC; Henriques, AC; Costa, FT; Morgado, E; Sousa, FT; Sousa, JP; da Costa, AG; Filipe, R; Garrido, J; Montalban, J; Ponce, P; Alves, R; Faria, B; Carvalho, MF; Pestana, M; Carvalho, F; Oliveira, JPAlport syndrome (AS) is caused by pathogenic mutations in the genes encoding α3, α4 or α5 chains of collagen IV (COL4A3/COL4A4/COL4A5), resulting in hematuria, chronic renal failure (CRF), sensorineural hearing loss (SNHL) and ocular abnormalities. Mutations in the X-linked COL4A5 gene have been identified in 85% of the families (XLAS). In this study, 22 of 60 probands (37%) of unrelated Portuguese families, with clinical diagnosis of AS and no evidence of autosomal inheritance, had pathogenic COL4A5 mutations detected by Sanger sequencing and/or multiplex-ligation probe amplification, of which 12 (57%) are novel. Males had more severe and earlier renal and extrarenal complications, but microscopic hematuria was a constant finding irrespective of gender. Nonsense and splice site mutations, as well as small and large deletions, were associated with younger age of onset of SNHL in males, and with higher risk of CRF and SNHL in females. Pathogenic COL4A3 or COL4A4 mutations were subsequently identified in more than half of the families without a pathogenic mutation in COL4A5. The lower than expected prevalence of XLAS in Portuguese families warrants the use of next-generation sequencing for simultaneous COL4A3/COL4A4/COL4A5 analysis, as first-tier approach to the genetic diagnosis of collagen type IV-related nephropathies.
- Fabry Disease Caused by the GLA p.Phe113Leu (p.F113L) Variant: Natural History in MalesPublication . Oliveira, J; Nowak, A; Barbey, F; Torres, M; Nunes, J; Teixeira-e-Costa, F; Carvalho, F; Sampaio, S; Tavares, I; Pereira, O; Soares, A; Carmona, C; Cardoso, MT; Jurca-Simina, I; Spada, M; Ferreira, S; Germain, DBackground, aims and methods: The α-galactosidase gene (GLA) c.337T>C/p.Phe113Leu variant was originally described in patients with late-onset cardiac forms of Fabry disease (FD), who had residual α-galactosidase activity. It has since emerged as the most commonly reported GLA variant in Portuguese subjects diagnosed with FD but is also prevalent in the Italian population, where two boys carrying the GLA Leu113 allele were identified in a large-scale newborn screening program, the variant allele segregating in both cases with the same surrounding haplotype. To further delineate the genotype-phenotype correlations of this GLA variant, we have reviewed the natural history and clinical phenotypes of 11 symptomatic Portuguese males, from 10 unrelated families originating from several different areas in mainland Portugal and Madeira Island, who were diagnosed with FD associated with the GLA Leu113 allele in a diversity of clinical and screening settings. Nine of the patients were the probands of their respective families. To test whether the GLA Leu113 allele inherited by the 10 Portuguese and the two Italian families resulted from independent mutational events, we have additionally performed a haplotype analysis with 5 highly polymorphic, closely linked microsatellite markers surrounding the GLA gene. Results and conclusions: Hemizygosity for the GLA Leu113 variant allele is associated with a late-onset form of FD, invariably presenting with severe cardiac involvement. Clinically relevant cerebrovascular and kidney involvement may also occur in some patients but the pathogenic relationship between the incomplete α-galactosidase deficiency and the risks of stroke and of chronic kidney disease is not straightforward. The observation that the Leu113 allele segregated within the same GLA microsatellite haplotype in both the Portuguese and Italian families suggests its inheritance from a common ancestor.