FRAGILE X CARRIER TESTING
For a common form of mental retardation

Fragile X Syndrome

This information is about fragile X syndrome and fragile X carrier testing. We hope that you find this information helpful, but if you have any questions please contact your doctor or a genetic professional.

What is fragile X syndrome?

Fragile X syndrome is the most common cause of inherited mental retardation, affecting approximately 1 in 4,000 males and 1 and 8,000 females. Often there is a family history of mental retardation, but sometimes there is no family history.

Fragile X syndrome causes a range of symptoms. Early signs include delayed speech and language. Intellectual abilities vary from mild learning disabilities to severe autism, hyperactivity and poor eye contact. Physical features, such as a long face or large or prominent ears, are usually more noticeable in adults than in children, and in males more then females.

How is fragile X syndrome inherited?

Fragile X syndrome is caused by a change in the Fragile X Mental Retardation (FMR1) gene. This altered gene can be passed from one generation to generation.

“Fragile X carrier” is a term used to describe someone who has an altered FMR1 gene, but does not show any obvious symptoms of fragile X syndrome. Women who are fragile X carriers have up to a 50% chance (or one in 2 chance) to have a child with fragile X syndrome. Men who are fragile X carriers pass the altered gene to all of their daughters but none of their sons. Daughters of carrier men are expected to be intellectually normal and are at risk to have affected children.

The genetics of fragile X syndrome are complicated. Genetic counseling is available when someone has a family history of fragile X syndrome or is shown to be a carrier of fragile X.

Can anyone be a fragile X carrier?

Yes. Fragile X syndrome is found among all ethnic backgrounds and racial groups. Approximately 1 in 260 women and 1 in 755 men in the general population is a carrier of the altered gene that causes fragile X syndrome. Additionally, women of all ages can have a child with fragile X syndrome, regardless of whether or not they have had previous healthy children.

Are certain people at greater risk to be a fragile X carrier?

Yes. Individuals are considered to have and increased risk to be a fragile X carrier if they have a:

- Family history of fragile X syndrome
- Family history of mental retardation, developmental delay or autism of unknown cause.

What is the fragile X carrier test?

The fragile X carrier test provides specific information about whether or not individuals are fragile X carriers, and, therefore, about their risks of having a child with fragile X syndrome. The test is performed on a small sample of blood and results are usually ready in two weeks.

Testing provides accurate results more than 99% of the time. Others cause of mental retardation are not identified through this test.

Occasionally, a person has carrier test results that fall in the range between normal and carrier. This is called and intermediate result. In these instances, the person will need to talk further with his/her doctor or genetics professional about the results.

Is prenatal testing available?

Yes. Prenatal testing by amniocentesis at about 16 weeks of pregnancy, or by chorionic villi sampling (CVS) at 10-12 weeks, can be performed to determine whether or not the unborn baby has inherited the fragile X gene.

Informed Consent /Decline for Fragile X Carrier Testing

You should be certain you understand the following point:

- The purpose of the test is to determine whether or not you are a fragile X carrier.
- The decision to have fragile X carrier testing is completely yours.
- The test does not detect all fragile X carriers, but does provide accurate results 99% of the time.
- The test may provide an “intermediate” result that may not give you definite information.
- If a patient is a carrier, prenatal testing is available to find out whether or not an unborn baby ha inherited the abnormal fragile X gene.
- The laboratory needs accurate information about your family history for the most accurate interpretation of the test results.
- No other test will be performed and reported on your sample unless authorized by my doctor, and any unused portion of your original sample will be destroyed within two months of receipt of the sample by the laboratory.
- The laboratory will disclose the test results ONLY to your doctor, or his/her agent, unless otherwise authorized by you or required by law.

Is fragile X testing required?

No. your doctor may recommend that you consider fragile X testing, but all testing is voluntary. The choice is yours.

For additional questions, your health care provider can help answer additional questions, or may refer you to a genetic counselor to:

- Review how fragile X is inherited
- Help you understand why fragile X testing has been recommended for you or your family member
- Explain your fragile X test results
- Explain your fragile X prenatal testing
- Discuss other you may have concerns.