Fragile X Syndrome (FXS)

What is fragile X syndrome (FXS)?

Fragile X syndrome is the most common form of inherited developmental disability that causes learning disabilities and cognitive impairment. It is a chronic condition, and unfortunately, only some people with FXS are able to live independently. Usually, males are more severely affected by fragile X syndrome than females.

What causes fragile X syndrome (FXS)?

FXS is caused by a defect in the FMR1 gene on the X chromosome. This mutation prevents the gene from properly making the fragile X mental retardation 1 protein, which plays an important role in the function of the nervous system. A lack of, or shortage of, this protein is what causes the symptoms of FXS.

What are the symptoms of fragile X syndrome (FXS)?

The first signs of fragile X syndrome are when babies miss developmental milestones. People with smaller changes in the gene may not even show signs of fragile X. People with larger changes have more severe symptoms, which may include:

• Developmental delays
• Stuttering
• Intelligence problems, such as learning disabilities or intellectual disabilities
• Social and emotional problems, such as anxiety, depression, or hyperactivity
• Speech and language problems, especially in boys

In addition to these symptoms, people with fragile X syndrome may have notable physical features, such as a large head circumference, protruding ears, forehead, and chin, flat feet, or an elongated face.

How is fragile X syndrome (FXS) diagnosed?

After children show signs of developmental delays or physical abnormalities at around three years of age, fragile X syndrome can be diagnosed by a genetic blood test, called the FMR1 DNA test.

What are the available treatments for fragile X syndrome (FXS)?

There is no cure currently available for fragile X syndrome, so treatment revolves around symptom management, mainly by helping people learn key language and social skills. If needed, a child can also take medications that are typically prescribed for behavior disorders like ADD or anxiety. These may include:

• Methylphenidate (Ritalin)
• Clonidine (Catapres)
• Selective serotonin reuptake inhibitors

Where can I find more information on fragile X syndrome (FXS)?

• U.S. National Library of Medicine
• Medline Plus
• Healthline