Browsing by Author "Oliveira, AC"
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- Combined study of ADAMTS13 and complement genes in the diagnosis of thrombotic microangiopathies using next-generation sequencingPublication . Fidalgo, T; Martinho, P; Pinto, CS; Oliveira, AC; Salvado, R; Borràs, N; Coucelo, M; Manco, L; Maia, T; Mendes, MJ; Del Orbe Barreto, R; Corrales, I; Vidal, F; Ribeiro, MLBACKGROUND: The 2 main forms of thrombotic microangiopathy (TMA) are thrombotic thrombocytopenic purpura (TTP) and atypical hemolytic uremic syndrome (aHUS). Deficiency of ADAMTS13 and dysregulation of the complement pathway result in TTP and aHUS, respectively; however, overlap of their clinical characteristics makes differential diagnosis challenging. OBJECTIVES AND METHODS: We aimed to develop a TMA diagnosis workflow based on ADAMTS13 activity and screening of ADAMTS13 and complement genes using a custom next-generation sequencing (NGS) gene panel. PATIENTS: For this, from a cohort of 154 Portuguese patients with acute TMA, the genotype-phenotype correlations were analyzed in 7 hereditary TTP (ADAMTS13 activity <10%, no inhibitor), 36 acquired TTP (ADAMTS13 activity <10%, presence of an inhibitor), and in 34 presumable aHUS. RESULTS: In total, 37 different rare variants, 8 of which novel (in ADAMTS13,CFH, and CD46), were identified across 7 genes. Thirteen TTP patients were homozygous (n=6), compound heterozygous (n=2), and heterozygous (n=5) for 11 ADAMTS13 variants (6 pathogenic mutations). Among the 34 aHUS patients, 17 were heterozygous for 23 variants in the different complement genes with distinct consequences, ranging from single pathogenic mutations associated with complete disease penetrance to benign variants that cause aHUS only when combined with other variants and/or CFH and CD46 risk haplotypes or CFHR1-3 deletion. CONCLUSIONS: Our study provides evidence of the usefulness of the NGS panel as an excellent technology that enables more rapid diagnosis of TMA, and is a valuable asset in clinical practice to discriminate between TTP and aHUS.
- Familial thrombotic risk based on the genetic background of Protein C Deficiency in a Portuguese StudyPublication . Fidalgo, T; Martinho, P; Salvado, R; Manco, L; Oliveira, AC; Pinto, CS; Gonçalves, E; Marques, D; Sevivas, T; Martins, N; Ribeiro, MLINTRODUCTION: Inherited protein C (PC) deficiency is a well-known risk factor for venous thrombosis (VT). Plasma PC levels are reliable in moderate to severe deficiencies; however, in mildly deficient individuals, the levels may overlap with those considered normal. Genetic studies of PROC, which encodes PC, could help identify carriers; genome-wide association studies (GWAS) have shown that approximately 50% of phenotypic variation in PC deficiency is caused by the cumulative effects of mutations in several other loci, namely in the PROCR. PATIENTS AND METHODS: With the main objective of determining the genotype/phenotype correlation in 59 Portuguese individuals from 26 unrelated families with history of thrombosis and repeatedly low/borderline PC plasma levels, we conducted a molecular study by direct sequencing of PROC; PROC promoter haplotypes and PROCR c.4600A>G polymorphism (rs867186), which are known to influence plasma PC concentrations, were also screened. RESULTS: Twelve different PROC mutations were identified, one of them not previously reported, p.Cys105Arg. The mutation types and locations as well as haplotype combinations correlated with the phenotypic severity. The most frequent mutation, p.Arg199X, correlated with the CGTC haplotype and was identified in nine families containing patients with higher numbers of VT episodes. This mutation in homozygous individuals for the CGTC haplotype is a significant risk factor for VT in Portuguese. CONCLUSION: These genetic family studies allowed the identification of the unknown carriers and individuals at a higher thrombotic risk within each family, thus permitting the evaluation of the need for prophylactic measures, particularly in at-risk situations.