Fragile X Syndrome

Fragile X syndrome affects a child's learning, behavior, appearance, and health. Symptoms can be mild or more severe. Boys often have a more serious form of it than girls.

Children who are born with this genetic condition can get special education and therapy to help them learn and develop like other kids. Medicines and other treatments can improve their behavior and physical symptoms.

What Are the Symptoms of Fragile X?

There are several, including:

  • Trouble learning skills like sitting, crawling, or walking
  • Problems with language and speech
  • Hand-flapping and not making eye contact
  • Temper tantrums
  • Poor impulse control
  • Anxiety
  • Extreme sensitivity to light or sound
  • Hyperactivity and trouble paying attention
  • Aggressive and self-destructive behavior in boys

Some children with fragile X also have changes to their face and body that can include:

  • A large head
  • A long, narrow face
  • Large ears
  • A large forehead and chin
  • Loose joints
  • Flat feet
  • Enlarged testicles (after puberty)

Symptoms are usually milder in girls. While most boys with fragile X have trouble with learning and development, girls usually don't have these issues.

Girls with fragile X sometimes have trouble getting pregnant when they grow up. They might also go into menopause earlier than usual.

This condition can also cause health problems like:

 

What Causes It?

The FMR1 gene, which is on the X chromosome, makes a protein called FMR that helps nerve cells talk to one another. A child needs this protein for his brain to develop normally. Children with fragile X make too little or none of it.

People with this condition also have more copies than usual of a DNA segment known as CGG. In most people, this segment repeats five to 40 times. In people with fragile X, it repeats more than 200 times. The more times this DNA segment repeats, the more serious the symptoms are.

A mother with the FMR1 gene change has a 50% chance of passing it to any of her children. A father can only pass it to his daughters.

Boys are more likely to have fragile X than girls, and they have more severe symptoms. This is because girls have two copies of the X chromosome. Even if one X chromosome has the gene change, the other copy can be fine. Boys have one X and one Y chromosome. If the X chromosome has the gene change, they will have symptoms of fragile X syndrome.

Some people inherit the fragile X gene without having symptoms. They are called carriers. Carriers can pass the gene change to their children.

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How Is It Diagnosed?

These tests can be done during pregnancy to see if an unborn baby has fragile X:

After the child is born, a blood test can diagnose fragile X syndrome. This test looks for the FMR1 gene change.

Babies born with fragile X syndrome don't always show signs of it. The doctor might notice that the baby's head is larger than usual. As the child gets older, learning and behavior problems can start.

What’s the Treatment?

No medicine can cure fragile X. Treatments can help your child learn more easily and manage problem behaviors. Options include:

  • Special education to help with learning (IEP and 504 are education plans that guide the school in providing support)
  • Speech and language therapy
  • Occupational therapy to help with daily tasks
  • Behavior therapy
  • Medicines to prevent seizures, manage ADD symptoms like hyperactivity, and treat other behavioral problems

The earlier you start treatment, the better. Work with your child's doctor, teachers, and therapists to make a treatment program. Your child might also qualify for free special education services.

To learn more about fragile X, join a support group. Or, reach out to an organization like the National Fragile X Foundation for advice and resources.

WebMD Medical Reference Reviewed by Renee A. Alli, MD on September 09, 2018

Sources

SOURCES:

CDC: "Facts about Fragile X Syndrome."

Cleveland Clinic: "Fragile X Syndrome."

Fraxa Research Foundation: "Are There Treatments for Fragile X Syndrome?" and "What Causes Fragile X Syndrome?"

March of Dimes: "Fragile X Syndrome."

National Fragile X Foundation: "Fragile X syndrome."

National Human Genome Research Institute: "Learning about Fragile X Syndrome."

U.S. National Library of Medicine: "Fragile X Syndrome."

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