How Does Fragile X Syndrome Affect People?

A wide range of characteristics are associated with Fragile X syndrome. However an individual person with Fragile X syndrome may only experience some of these characteristics, and the degree to which a person may be affected by Fragile X syndrome will vary.

Developmental disability is the key presentation of Fragile X syndrome, and typically in males includes intellectual disability. Females commonly appear less affected by Fragile X syndrome, but this is not always the case and some will be severely affected.



  • Developmental delay
  • Learning difficulties
  • Intellectual disability
  • Speech and language difficulties
  • Fine and gross motor issues
  • Difficulty with coordination


  • Anxiety
  • Attention Deficit Hyperactivity Disorders (ADHD)
  • Autism spectrum disorders, autistic type behaviours
  • Hyperarousal
  • Difficulty with eye contact
  • Mood instability
  • Sensory processing issues including aversion to touch, loud noises, bright lights


There are some physical features associated with Fragile X syndrome, but they may be subtle or not present:

  • Low muscle tone and loose joints
  • Vision and hearing issues
  • Long narrow face, prominent ears (older males)
  • Flat feet
  • Large testicles (post-pubescent males)
  • Mitral valve prolapse



About one-third of females with Fragile X syndrome have a significant intellectual disability. Others may have moderate or mild learning disabilities, emotional/mental health issues, general anxiety, and/or social anxiety.


Characteristics seen in males with Fragile X syndrome can also be seen in females, though females often have milder intellectual disability and a milder presentation of other characteristics.

A small percentage of females with Fragile X syndrome full mutation will have no apparent signs of the condition—intellectual, behavioural, or physical. These females are often identified only after another family member has been diagnosed.

To learn more:

Understanding Fragile X 

Video produced by Fragile X Association of Australia

About Fragile X syndrome

Video produced by Fragile X Society UK (7 minutes)

Fragile X syndrome

Article from Medical Observer journal

Females with Fragile X syndrome

Video produced by Fragile X Society UK (5 minutes)


World Fragile X Day!

22 July | Celebrating everyone living with Fragile X and acknowledging the work being done to ensure early diagnosis and access to future treatments. Your support will help enable us to provide support to the Fragile X community around Australia through our HelpLine, specialist counselling, peer connections, educational webinars, referrals and advocacy. We are grateful for your lead.

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