Fragile X syndrome is the leading hereditary cause of developmental disabilities in all populations. The absence of a functional fragile X gene shuts off production of a special protein in the brain needed for normal cognitive development. Without this protein, children with the syndrome will never learn normally, despite hours of therapy and rehabilitation. Visit the links at right to learn more about this common genetic condition.

What is Fragile X

In 1991, scientists discovered the gene (called FMR1) that causes Fragile X. In individuals with Fragile X Syndrome, a defect in FMR1 (a full mutation) shuts the gene down. Like a defective factory, the FMR1 gene cannot manufacture the protein that it normally makes. Some individuals are fragile X carriers; they have a small defect in the FMR1 gene (called a premutation) but do not show symptoms of Fragile X .

Fragile X is inherited. Carrier men (transmitting males) pass the premutation to all their daughters but none of their sons. Each child of a carrier woman has a 50% chance of inheriting the gene. The Fragile X premutation can be passed silently down through generations in a family before a child is affected by the syndrome. A DNA blood test identifies both carriers and affected individuals. While the exact prevalence of Fragile X is unknown, recent studies indicate the statistics below:

1 in 2000 boys and 1 in 4000 girls are estimated to be affected.
1 in 260 women are carriers.

1.The FMR-1 gene is located on the X chromosome. This gene is responsible for instructing the cell to make FMRP, a protein assumed to be essential for normal brain functioning.
2.The genetic code for the FMR-1 gene usually contains a limited repetition of CGG sequences. The normal range is 5-50 repeats.
3. Some people have an expanded number of CGG repeats. When the number of CGG repeats is between 50 and 200 the individual is a premutation carrier of fragile X syndrome. Carriers are not usually affected by fragile X syndrome, but they are at risk of having affected children.
4. If the number of repeats exceeds 200, usually this disrupts the code and prevents the production of the FMR protein. These individuals have the full mutation and usually are affected by fragile X syndrome.

The Effects Of Fragile X

Fragile X is the leading form of autism of known cause: 90 % of Fragile X patients have autistic features, 50% of pre-school Fragile X children meet autism diagnostic criteria, and 6% of all autistic individuals turn out to have fragile X. Fragile X also gives rise to anxiety disorders, attention deficit hyperactivity disorder, psychosis, obsessive-compulsive disorder, and many other problems.

Is There a Cure for Fragile X Syndrome?

There is currently no cure for Fragile X Syndrome, although appropriate education and medications can help maximize the potential of each child. However, most boys and many girls remain significantly affected throughout their lives. The cost to society for treatment, special education, and lost income is staggering. The need for research aimed at treatment is urgent. Recent significant progress has been made in understanding mechanisms and developing potential treatments for inherited diseases that are caused by a single gene, such as Fragile X. Current medical research focuses on: Gene Therapy - studying the gene that causes Fragile X in order to determine whether a healthy gene may be inserted into the cells of affected individuals, thereby replacing the mutated, ineffective gene. Protein Replacement Therapy - studying the protein product that is lacking due to the mutation, in hopes that the protein may be supplemented from an external source. Psychopharmacology - treating the symptoms of the disorder with medications.

Many researchers believe that medical treatment, when it becomes available, will be able to help Fragile X individuals of all ages. Experts think that the missing FMR protein has a regulatory function in the brain, rather than a structural function, and that this protein is needed throughout a person's life.