![](https://webarchive.library.unt.edu/web/20090115161248im_/http://www.cdc.gov/ncbddd/homepage_includes/images/core/s.gif) |
Single Gene Disorders and Disability (SGDD) |
What
is Fragile X syndrome?
Fragile X syndrome (FXS) is the most common known cause of
intellectual disability, also known as mental retardation, and
developmental disability that can be inherited (passed from one
generation to the next). The exact number of people who have FXS is
unknown, but it is estimated that about 1 in 4000 males and 1 in
6000 to 8000 females have the disorder. Although FXS occurs in both
males and females, females generally have milder symptoms. Signs
that a child has FXS include not sitting, walking, or talking as
early as other children. This is known as having developmental
delays. Often, there are other physical and behavioral signs, but
features of FXS vary and signs can be subtle and easy to miss.
Children often have a typical facial appearance that gets more
noticeable with age. These features include a large head, long face,
and prominent ears, chin, and forehead. Children who have FXS might
also have learning disabilities, speech and language delays, and
behavioral problems such as attention-deficit/hyperactivity disorder
(ADHD).
Males who have FXS usually have some degree of intellectual
disability that can range from mild to severe. Females with FXS can
have normal intelligence or some degree of intellectual disability
with or without learning disabilities. Autism spectrum disorders (ASDs)
also occur more frequently in children with FXS.
|
|
|
[Return to top of page]
Date: September 1, 2006
Content source: National Center on Birth Defects and Developmental
Disabilities
|
![](https://webarchive.library.unt.edu/web/20090115161248im_/http://www.cdc.gov/ncbddd/homepage_includes/images/core/s.gif) |
|