Fragile X syndrome
Do changes in the fragile X mental retardation 1 gene cause fragile x syndrome?
The CGG trinucleotide repeat expansion and hypermethylation (turning off) of the promoter region of the FMR1 gene does not predispose to fragile X syndrome, it causes fragile X syndrome. If a person has the full mutation of greater than 200 CGG repeats, that person has a diagnosis of fragile X syndrome. What symptoms of fragile X syndrome a person shows and how affected they are can vary, even between individuals in the same family. Some persons may be more mildly affected and have fewer symptoms, and some persons may be more severely affected and have many symptoms, but all individuals with greater than 200 repeats in their FMR1 gene are said to have fragile X syndrome. For more information about the signs and symptoms of fragile X syndrome, please visit The National Fragile X Foundation.