What is FXS?

FXS (Fragile X Syndrome) is a genetic disorder characterized by mild-to-moderate intellectual disability. It is more affected in males, however, females may also be affected by the condition but usually to a lesser extent. There is no cure for this disorder and early intervention is recommended so that there is an opportunity for developing a full range of skills.

What causes FXS?

FXS is caused by a mutation in the FMR1 (fragile X mental retardation 1) gene which is located on the X chromosome. The protein made by the FMR1 gene has a role in the development of the brain (connections between neurons). When there is an expansion of the CGG triplet repeat within the FMR1 gene, it may results in learning disabilities and cognitive impairment. This abnormal gene, which can be passed from generation to generation, is usually inherited through the gene that is carried by women.

How is fragile X syndrome inherited?

A fragile X carrier is someone who has an altered FMR1 gene, but does not display or show any obvious symptoms of FXS. Women who are fragile X carriers have up to a 50% chance of having a child with FXS. Men who are fragile X carriers will pass the altered gene to all of their daughters but none of their sons. Daughters of carrier men are expected to be intellectually normal but are at risk of having children affected with fragile X syndrome.

Carrier Rate:

About 1 in 800 male

About 1 in 260 female

This test is recommended for people who:

• Would like to understand their risk of having a child with FXS.
• Have a family history of FXS.
• Have a family history of mental retardation, developmental delay or autism of unknown cause.
• Have infertility problems associated with elevated follicle stimulating hormone (FSH) levels or premature ovarian failure (POF).
• Have a family history of adult onset ataxia and/or tremors.
• Are considering pregnancy or already pregnant.
• Are planning to use/ donate eggs, sperm, or embryos.