Fragile X Syndrome, also known as Martin-Bell Syndrome, is the most common form of inherited intellectual and developmental disability (IDD).  It is called Fragile X Syndrome (FXS) because part of the X chromosome looks broken or fragile when viewed through a microscope.  It is caused by changes in the FMR1 gene, which usually makes a protein called FMRP. FMRP is needed for brain development.  People who have Fragile X Syndrome do not make this protein.

 

Researchers estimate that about 1 in 8,000-11,000 females and 1 in 4,000-7,000 males have Fragile X Syndrome. FXS is usually more severe in males. It is not clear how many people carry the fragile X premutation, which can be passed down to their child and cause fragile X. Parents carrying the premutation are nearly two times more likely to have a child with a disability.

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Fragile X Syndrome affects a child’s intelligence, mental health, physical features, and behavior. Signs that a child might have FXS include:

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• Developmental delays;

• Learning disabilities, like trouble learning new skills;

• Social and behavioral problems, like not making eye contact, anxiety, trouble paying attention, and hand flapping; and

• Physical features such as a long, narrow face, a large forehead, a large jaw, soft skin, and/or flat feet.