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What is Fragile X Syndrome?

Marketing Intern | Shield HealthCare
03/05/18  11:30 AM PST
What is fragile X syndrome

What Causes Fragile X Syndrome?

Fragile X syndrome is the number one inherited cause of intellectual disabilities, affecting about 1 in 4,000 males and 1 in 8,000 females. Fragile X can also be found among all racial and ethnic groups.

A genetic mutation causes Fragile X syndrome, where a DNA segment expands beyond a certain length. This DNA segment repeats 5 to 40 times in people without the syndrome — but in people with fragile X syndrome, it repeats over 200 times. This segment’s abnormal expansion prevents the gene from producing a key protein. The lack of this protein leads to symptoms of fragile X syndrome.

The symptoms among people with fragile X vary. People with a small change in the gene might not show any signs of fragile X, while those with bigger changes can have moderate to severe symptoms.  Fragile X affects both males and females, but fragile X affects males more than females – in part because most most males only carry one X chromosome.

Diagnosis of Fragile X Syndrome

Intellectual disability is the syndrome’s primary indication. There are few signs in babies, but one of the most common signs is an abnormally large head. The average age of diagnosis for males is 35-37 months (3 years), while girls are typically diagnosed around 41.6 months (3 1/2 years).

A genetic test (“polymerase chain reaction,” or PCR) can identify and diagnose fragile X syndrome by looking for an expanded gene in the FMR1 gene.

Related article: Father of Two Sons With Fragile X Syndrome Wins Story Contest Grand Prize

Male Symptoms and Traits

Physical traits can include

  • large head size
  • long face
  • prominent forehead and chin
  • protruding ears
  • large testes (after puberty)
  • flat feet
  • loose or hyper-flexible joints

Physical problems can include

  • eye, orthopedic, heart, and skin problems
  • ear infections
  • tremors
  • poor coordination

Pre-pubescent behavioral traits can include

  • social anxiety
  • hand biting or flapping of hands
  • hyperactivity
  • temper tantrums

Post-pubescent behavioral traits can include

Other traits of fragile X syndrome include friendly and social behavior, strong imitation skills, and a strong visual and long term memory.

Female Symptoms and Traits

  • Females display some traits of males, however, females typically have milder intellectual disabilities and less behavioral and physical features than men.
  • Approximately one-third of females with fragile X have serious intellectual disabilities.
  • Some females may only have mild learning disabilities and emotional/mental health issues such as general or social anxiety.
  • A minor percentage of females who have the full genetic mutation will not have any signs of the syndrome. These patients may only be diagnosed after another family member has been diagnosed.


  • There is no definitive treatment for fragile X syndrome. There is supportive therapy for people with this syndrome that includes:
    • Specialized education and anticipative management (e.g., avoidance of extra and unnecessary stimulation that may increase behavioral problems).
    • Medications that can decrease behavioral problems (no specific medication has been proven more effective than another).
    • Intervention and vocational training.
    • Any visual, hearing, connective tissue, or heart problems are treated normally.

Health risks

  • Women have an increased risk of premature ovarian failure and menopause (starting before the age of 40).
  • Men have an increased risk of developing fragile X tremor ataxia syndrome, which causes tremors that worsen over time. These tremors can lead to difficulty in walking and balance.
  • Males also have a higher chance of getting dementia.

Additional  resource: Think Fragile X