The clinical and genetic study of fragile X syndrome

Fragile X syndrome (FXS). is the most common cause of inherited mental retardation. FXS is mainly caused by the massive expansion of CGG-repeats located in the 5'untranslated region in the fragile X mental retardation-1 (FMR1) gene. We carried out a clinical and genetic study of 214 children from Bashkortostan with mental retardation of unknown etiology. Molecular genetic diagnostic included screening with PCR analysis of CGG-repeats length and methylation sensitive polymerase chain reaction (ms-PCR) for the detection of CpG-island methylation in the FMR1 and FMR2 genes. Nine patients (4,2%) with full mutation were identified. This result is consistent with the prevalence of the FXS in Caucasian populations in which it is estimated as 2,6 to 8,7% among retarded males. This screening method proved to be useful for the diagnostic of FXS. Furthermore, our clinical findings confirmed that autistic-like behaviors, hyperactivity and speech dysfunction were stable phenotypic features of FXS.