Fragile X syndrome is the leading known inherited cause of mental retardation. The condition is due to a lengthening of a gene on the X chromosome, one of the set of chromosomes which determine the gender of a person.

The lengthening of the Fragile X Mental Retardation gene (FMRP1) shuts off the ability of brain cells to make a protein necessary for normal brain functioning. The effects of the shortage or lack of this protein range from mild learning disabilities to severe autistic tendencies.

There is no cure for fragile X syndrome, but many early intervention therapies and newer medications can help alleviate some of the effects and allow many persons to lead productive lives.

Fragile X syndrome is a fertile research area in the booming field of genetics.  This page guides you to the major fragile X sites on the web, originating in the U.S.  In addition some more specialized medical and research sites are listed. 

A separate page is devoted to local and regional support groups in the United States.

The FX International page lists sites originating from other countries.

Fragile X syndrome is just one of many developmental disabilities. Because many persons affected by fragile X have autistic-like symptoms, it is often listed among the autism spectrum disorders.

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FRAXA Research Foundation
FRAXA is a foundation of parents dedicated to research to find a cure for fragile X syndrome. Basic information is available in a number of other languages. This site also contains instructions for joining a free e-mail list of parents and professionals who support each other and exchange information about fragile X. Another excellent source of information.

National Fragile X Foundation
The National Fragile X Foundation is the oldest advocacy group on fragile X syndrome. This site contains a comprehensive overview of fragile X syndrome as well as summaries of the latest research from the biennial international conference it sponsors. Much of the information is of great practical value to parents and professionals alike.

GeneClinics article on Fragile X Syndrome
Complete summary of current knowledge on fragile X syndrome. Includes plenty of technical details and a fairly extensive list of source citations.

Your Genes, Your Health: Fragile X Syndrome
Animated presentation with basic information about fragile X syndrome.