Fragile X Syndrome

Fragile X syndrome (FXS) is a genetic condition that causes intellectual disability, behavioral and learning challenges and various physical characteristics. Though FXS occurs in both genders, males are more frequently affected than females, and generally with greater severity.

Features of Fragile X Syndrome in Males

  • The majority of males with fragile X syndrome demonstrate significant intellectual disability (formerly referred to as “mental retardation”). Disabilities in FXS include a range from moderate learning disabilities to more severe intellectual disabilities.
  • Physical features may include large ears, long face, soft skin and large testicles (called “macroorchidism”) in post-pubertal males. Connective tissue problems may include ear infections, flat feet, high arched palate, double-jointed fingers and hyper-flexible joints.
  • Behavioral characteristics can include ADD, ADHD, autism and autistic behaviors, social anxiety, hand-biting and/or flapping, poor eye contact, sensory disorders and increased risk for aggression.
  • No one individual will have all the features of FXS, and some features, such as a long face and macroorchidism, are more common after puberty.

Features of Fragile X Syndrome in Females

  • The characteristics seen in males can also be seen in females, though females often have milder intellectual disability and a milder presentation of the syndrome’s behavioral and physical features.
  • About one-third of females with FXS have a significant intellectual disability.
  • Others may have moderate or mild learning disabilities, emotional/mental health issues, general anxiety and/or social anxiety.
  • A small percentage of females who have the full mutation of the FMR1 Gene that causes FXS will have no apparent signs of the condition—intellectual, behavioral or physical. These females are often identified only after another family member has been diagnosed.

Moving Forward

While individuals with FXS will experience a number of challenges in their lives, given effective interventions and support they can be engaging and productive members of their families, schools, workplaces and communities as highlighted below in these images and in our Faces of Fragile X section.