Fragile X Syndrome

Fragile X syndrome (FXS) is the most common known cause of intellectual disability (formerly referred to as mental retardation) that can be inherited. It is estimated that FXS affects about 1 in 4,000 boys and 1 in 6,000to 8,000 girls. Both boys and girls can have FXS, but girls usually are more mildly affected.

The cause of FXS is genetic. FXS occurs when there is a change in a gene on the X chromosome called FMR1. This gene makes a protein needed for normal brain development. In FXS, the FMR1 gene does not work properly. The protein is not made, and the brain does not develop as it should. The lack of this protein causes FXS.

The Centers for Disease Control and Prevention offers this list of signs that children with FXS might:

·         Sit up, crawl, or walk later than other children

·         Have trouble with learning and solving problems

·         Learn to talk late, or have trouble speaking

·         Become very anxious is crowds and new situations

·         Be sensitive about someone touching them

·         Bite or flap their hands

·         Have trouble making eye contact

·         Have a short attention span

·         Be in constant motion and unable to sit still

·         Have seizures

Some children with FXS have certain physical features such as:

·         A large head

·         A long face

·         Prominent ears, chin, and forehead

·         Flexile joints

·         Flat feet

·         Macroorchidism (enlarged testicle in males; more obvious after puberty)

Children with FXA might also have behavioral problem such as ADHD and anxiety. Some males can develop aggressive behavior. Depression can also occur. Boys with FXS usually have a mild to severe intellectual disability, while many girls with FXS have normal intelligence. Autism spectrum disorders occur more often among children with FXS.

For more information contact the National Information Center for Children and Youth with Disabilities at www.nichcy.org/states.htm or call the CDC at 1-800-232-4636.