Five Things You May Not Know about Fragile X Syndrome

What to know

Fragile X syndrome (FXS) is a genetic disorder. Because of changes in their genetic material (specifically the FMR1 gene), people who have FXS do not make a protein called FMRP, which is needed for normal brain development. People who have other fragile X-associated disorders also have changes in the FMR1 gene but usually make some of the FMRP protein.

family sitting together with three kids that have fxs

Five things you may not know about fragile X syndrome

As part of CDC's work to educate people about fragile X syndrome (FXS), here are five things you may not know about FXS.

Graphic of a fragile x syndrome chromosome
Fragile X syndrome (FXS) is a genetic disorder.

#1 FXS is genetic, but there isn’t always a family history.

FXS means that a particular part of person's FMR1 gene is much larger than usual. This part of the FMR1 gene ranges in size from person to person and can become bigger from one generation to the next. Therefore, many people with FXS have no family members with FXS symptoms. In some people who do not have FXS, this part of the FMR1 gene is a little larger than usual. These people are said to have a "premutation" in the FMR1 gene. FMR1 premutations run in families, and women with a premutation may give birth to children with FXS. Some people with a premutation have symptoms of fragile X-associated disorders, such as tremors and, in women, early menopause, although these symptoms are most commonly due to other causes.

#2 Babies aren’t routinely tested for FXS, so families might not find out about FXS for a few years.

FXS requires a special blood test that is not usually included in the genetic tests that a pregnant woman gets or in the tests that are routinely done right after a baby is born. The only way to diagnose FXS is with a special blood test called the "FMR1 DNA Test for Fragile X." The American Academy of Pediatrics recommends that children diagnosed with general developmental delays, intellectual disability, or autism spectrum disorder (ASD) receive a genetic test for FXS.

#3 Not everyone who has FXS has the same symptoms, and FXS doesn’t just affect boys.

Both boys and girls can have FXS. FXS is more common in boys, and the symptoms are usually more severe in boys than in girls. Boys with FXS usually have some degree of intellectual disability, whereas girls range from normal intelligence to having an intellectual disability. But both boys and girls can have symptoms that range from mild to severe.

#4 There is no cure for FXS, but an early diagnosis can still help.

Even though there is no cure for FXS, there are educational, behavioral, and therapeutic services which can help. A diagnosis may also help families with family planning and connecting with support groups of other families affected by FXS. Learn more.

#5 CDC works with researchers and the FXS community to improve the lives of people with the condition and their families.

To help individuals and families affected by FXS, we need to learn more about other conditions that commonly occur with FXS, the day-to-day lives of people living with FXS and their families, and the types of intervention and support that are most effective for individuals with FXS and their families.

What CDC is doing

CDC building in Atlanta, GA
Information collected by the FORWARD study has answered important questions for individuals with FXS and their families.

CDC activities include:

Supporting the National Fragile X Foundation to develop the Fragile X Online Registry With Accessible Research Database (FORWARD).

  • Because FXS is a rare disorder—meaning that there are fewer than 200,000 newly identified cases per year in the United States—researchers who want to learn more may have difficulty finding enough affected individuals to get answers to scientific questions. The FORWARD database now includes carefully collected clinical, demographic, and behavioral information on more than 1,700 children and adults with FXS enrolled at fragile X specialty clinics throughout the United States.
  • The information in the FORWARD database can be used to better understand many of the unanswered questions about FXS, and to find ways to improve the health and quality of life of people with FXS and their relatives and caregivers.
  • Recent studies published in medical and scientific journals have used information from FORWARD to help answer questions that are important to individuals with FXS and their families (for example, what medications are most typically used to treat children with FXS with challenging behaviors such as irritability, agitation, aggression, and self-injury, and what to expect with toilet training efforts in children with FXS). Learn more about research studies using the FORWARD database.

FORWARD-MARCH: The Next Step in Fragile X Syndrome Research

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