Fragile X Syndrome – Symptoms and Signs

Individuals living with Fragile X syndrome may experience a range of behavioral and health challenges.


  • intellectual disabilities, ranging from mild to severe
  • attention deficit and hyperactivity, especially in young children
  • anxiety and unstable mood
  • autistic behaviors, such as hand-flapping and not making eye contact
  • sensory integration problems, such as hypersensitivity to loud noises or bright lights
  • speech delay, with expressive language more severely affected than receptive language
  • seizures (epilepsy) affect about 25% of people with Fragile X syndrome

Physical Signs

These features may be hard to recognize in babies and young children, but sometimes become more apparent with age. Not everyone with Fragile X has all these signs.

  • long face, large prominent ears, flat feet
  • hyperextensible joints, especially fingers
  • low muscle tone
  • males may have large testes after puberty

Girls are Often Less Affected than Boys

Girls generally have milder symptoms than boys, although there is a lot of variation and no good way to predict this. While most boys have intellectual impairment, only one-third to one-half of girls have significant intellectual challenges. The rest have either normal IQ or learning disabilities. Math is often a particular challenge for girls. Emotional and behavioral problems are common in both sexes.

About 30% of boys with Fragile X meet full criteria for autism. Most boys and some girls have some symptoms of autism, but many tend to be very social and interested in other people.

Both boys and girls may have delays in learning how to talk, but most individuals with Fragile X do learn to speak.

Learn More

According to the Centers for Disease Control (CDC), “More families caring for a child with Fragile X syndrome report excessive financial expense as compared to families caring for a child with autism spectrum disorder, with an intellectual disability, or those caring for a child with both autism spectrum disorder and intellectual disability”. The need for more research and resources is urgent.

Nuno has Fragile X Syndrome
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