May also be called: FXS, Martin-Bell Syndrome, Escalante’s Syndrome, Marker X Syndrome, FRAXA Syndrome

Fragile X syndrome is a genetic birth defect. It causes mental impairment, such as learning disabilities, intellectual disability, autistic behaviors, and problems with attention and hyperactivity.

More to Know

Genes are like chemical blueprints that affect how the body looks and works. Fragile X syndrome happens because of a defect in a gene that makes a protein important to brain development. The body of a child with fragile X syndrome doesn't make this protein. As a result, the child has some degree of mental impairment, which can range from mild to severe.

Children with fragile X have different features that include a long face, large ears, flat feet, and extremely flexible joints, especially fingers. Boys have the syndrome more often than girls and are more likely to have serious intellectual disability. Both boys and girls are likely to have emotional and behavioral problems.

Some states screen newborns for fragile X syndrome, but sometimes the condition isn't found until the toddler years. Children with developmental delays may be referred for genetic testing that can identify fragile X. Treatment depends on the severity of the mental impairment and the symptoms it causes. Kids with fragile X syndrome often get therapy to learn important skills and medicine to help with some behavioral issues.

Keep in Mind

Early diagnosis and a treatment plan that includes parents, caregivers, teachers, and others close to them can help kids with fragile X reach their full potential. There is no cure, but research continues into ways to prevent it and manage the complications.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.