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Keywords: Fragile X syndrome and FXTAS; Triplet and other repeats; Genetic epidemiology; Molecular cytogenetics; Intellectual and developmental disability

G.F.S. Carvalho 1; A.T. Dias 1; S.N. Chehimi 1; Y. Gasparini 1; E.A. Zanardo 1; M.V. Souza 1; M.M. Montenegro 1; A.M. Nascimento 1; A.B. Freitas 2; F.A.R. Madia 1; G.M. Novo-Filho 1; L.D. Kulikowski 1

1) Laboratório de Citogenômica, Departamento de Patologia, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, BR; 2) Departamento de Obstetrícia e Ginecologia, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, Sao Paulo, SP, BR

Background: Fragile X Syndrome (FXS) is the second leading cause of intellectual disability (ID), affecting 1: 5000-7000 men and 1: 4000-6000 women. An alteration of the FMR1 gene at Xq27.3 cause the FXS. Most of patients present CGG expansion (> 200 triplets) in the 5 'UTR of the gene, the other patients present FMR1 mutations and duplication / deletion in the same genomic region. Diagnostic detection using commercial kits allows the unambiguous identification of patients and carriers, while prenatal and neonatal diagnoses are a challenge. Clinical features comprise global developmental delay, anxiety and hyperactive behavior. Characteristic facies include large ears, a long face, a prominent jaw and forehead and flat feet. Material and Methods: We evaluated 63 patients with intellectual disability associated with neuropsychomotor developmental delay and / or other (FXS) clinical features, both sexes and without age restriction, using FragilEase® kits (Perkin Elmer, Massachusetts, USA) or Amplidex® (Asuragen , Texas, USA). The results show four evils with full CGG expansion (> 200 repeats), two patients with intermediate alterations, ranging from 45 to 54 repeats and one patient with pre mutation (range from 55 to 200 repeats). Four females showed alleles in heterozygosis. Discussion: Our study revealed the prevalence of 6.3% of complete mutations, and for non-complete mutations, we identified a percentage of 11.1%. The obtained results corroborated data reported in the literature, but the overall detection rate was higher than the rates previously reported, highlighted the importance of the criteria used to select patients.