Fragile X Syndrome (FXS) is the most common inherited cause of learning disability, affecting around 1 in 4,000 males and 1 in 8,000 females. It can cause a wide range of learning difficulties as well as social, language, emotional and behavioral problems.
FXS is caused by a defect in a gene that makes a brain protein needed for development. The mutated gene is located on the X chromosome and is called the FMR1 gene.
For more information you can visit the Fragile X Society website.