ABSTRACT

Fragile X Syndrome (FXS), the most common cause of inherited intellectual disability, is a genetic developmental disorder, normally transmitted matrilineally and characterised by particular physical features, autistic behaviours, attention problems, hyperactivity, social anxiety and distinctive neurocognitive deficits. The condition, also known as Martin-Bell syndrome, is caused by alterations in the Fragile X Mental Retardation 1 gene (FMR1) located on the long arm of the X chromosome, which disrupt the synthesis of a functional Fragile X Mental Retardation Protein (FMRP), the product of the affected gene. Fragile X Syndrome is an X-linked inherited disorder associated with intellectual disability, autistic features, behavioural and social challenges and particular physical characteristics. The disorder, transmitted mainly matrilineally, is due to mutations in the FMR1 gene, the most frequent being the expansion in the number of consecutive cytosine-guanine-guanine (CGG) repeats in the 5' untranslated region (5'UTR).