Fragile X syndrome (FXS), also known as Martin-Bell syndrome, is the most common cause of inherited intellectual disability. FXS is caused by a change in a gene on the X chromosome. This change means the body can't make a protein needed for normal brain development.
FXS affects both males and females, but is more common in males. FXS can lead to:
social and behavioral problems
People with FXS also may have other conditions, including: