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 results in an inability to make a protein needed for
normal brain development.
FXS affects both males and females, but is more common in males. FXS can result
social and behavioral problems
People with FXS also may have other conditions, including: