• X-linked dominant genetic disorder caused by changes to the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene

  • The FMR1 gene, located on the X chromosome, normally contains between 5 and 44 CGG nucleotide-triplet repeats, although the number varies from person to person, but people with FXS can have more than 200 CGG repeats, which causes the FMR1 gene to "turn off"

    • The FMR1 gene makes a protein (FMRP) that is critical for brain development; FMRP is not produced, or produced in extremely limited amounts, in people with FXS​

      • Fragile X-Associated Disorders are characterized by changes to the FMR1 gene, but some FMRP is still produced

        • There are often abnormal numbers of CGG triplet repeats in the FMR1 gene​

• The exact number of people affected with FXS is unknown and estimates vary

  • Affects an estimated 1 in 4,000-7,000 males and 1 in 6,000-11,000 females in the U.S.

    • More males are affected with FXS and have more significant symptoms, but more females seem to be carriers of altered FMR1 genes​

  • Affects people from all ethnic backgrounds

• Symptoms:

  • Developmental delays

    • Sitting, walking, talking, etc. later than peers​​

  • Learning disabilities

  • Social and behavioral challenges 

  • Intellectual disabilities

    • Ranges from mild to severe in males; less common and less significant in females​

  • Males may have a large head, long face, protruding ears, and other physical characteristics

    • May not be apparent until after puberty​

  • Associated with Autism Spectrum Disorder (ASD)

• Diagnosed by analyzing DNA acquired through a blood sample​

  • Looks for more than 200 CGG nucleotide triplets on the FMR1 gene​​

• Most patients are diagnosed before the age of 2

• No cure exists

  • Treatments aim to improve skills such as walking, talking, and social interaction

    • Early intervention is extremely important but treatment at any age can be beneficial​

  • Medications can be used to help manage behavioral challenges

 
Sources
Center for Disease Control (CDC)

NORD​