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What Is Fragile X Syndrome?

Medically Reviewed by Dan Brennan, MD on June 01, 2022

Fragile X syndrome is a condition that affects a child's learning, behavior, appearance, and health. Symptoms can be mild or more severe. Doctors also call it Martin-Bell syndrome. 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 Syndrome?

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
  • Depression
  • Obsessive-compulsive behaviors
  • Extreme sensitivity to light or sound
  • Hyperactivity and trouble paying attention
  • Aggressive and self-destructive behavior in boys
  • Trouble picking up on social cues
  • Seizures
  • Attention deficit disorder (ADD)
  • Autism symptoms that affect communication and how they deal with other people

Fragile X Syndrome and Autism

More people with fragile X have autism compared to those without the condition. Fragile X can sometimes cause autism. And if your child has autism, they have a 2%-6% chance of also having fragile X syndrome.

If your child has both fragile X and autism, they’re more likely to have seizures, sleep issues, more behavioral issues, and need more medications.

Almost 80% of children with fragile X also have attention deficit disorder (ADD) or attention deficit hyperactivity disorder (ADHD).

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

  • A large head
  • A long, narrow face
  • Soft skin
  • Crossed or lazy eyes
  • Low muscle tone
  • A high-arched roof of their mouth
  • Large ears
  • A large forehead and chin
  • Loose joints
  • Flat feet
  • Enlarged testicles (after puberty)

Signs of fragile X usually start with delayed speech and language trouble by the age of 2. Boys are usually diagnosed around 35-37 months old. Girls are diagnosed around 42 months old. 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 problems like:

  • Hearing problems
  • Vision problems
  • Heart problems
  • Sleep problems
  • Obesity

What Causes Fragile X Syndrome?

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 their 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 their children. A father can only pass it to 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.

What Are the Risk Factors for Fragile X Syndrome?

The number isn’t clear, but about 1 in 8,000 to 11,000 females have fragile X syndrome, while 1 in 4,000 to 7,000 males have the condition.

There aren’t any risk factors for fragile X that you can control. If you have the FMR1 gene, your child could have it, too.

There’s no way to prevent fragile X syndrome.

How Do Doctors Diagnose Fragile X Syndrome?

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

  • Amniocentesis -- doctors check a sample of amniotic fluid for the FMR1 gene change
  • Chorionic villus sampling (CVS) -- doctors test a sample of cells from the placenta to check for the FMR1 gene

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 for Fragile X Syndrome?

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.

What’s the Outlook for People With Fragile X Syndrome?

The symptoms of fragile X aren’t life-threatening. Your life expectancy with the conditions is the same for anyone without it.

A lot of people with the condition are able to live successful lives on their own. About 8 out of 20 women and 1 in 20 men with fragile X don’t need help with daily activities.

People with the condition can go to school, have conversations, read books, learn new ideas, and finish other tasks by themselves.

How Can You Find Support With Fragile X Syndrome?

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.

There, you can learn about local events and groups for people with fragile X.

There are also resources for parents. If you recently found out that your child has fragile X, this site offers many tips, videos, and firsthand experiences to help you understand how to care for them.

Show Sources

SOURCES:

CDC: "Facts about Fragile X Syndrome."

Cleveland Clinic: "Fragile X Syndrome."

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

March of Dimes: "Fragile X Syndrome."

National Fragile X Foundation: "Fragile X syndrome,” “Newly Diagnosed.”

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

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

The Children’s Hospital of Pittsburgh: “Managing Attention Deficit Hyperactivity Behaviors in Children with Fragile X Syndrome.”

Medline Plus: “Fragile X Syndrome.”

National Organization for Rare Disorders: “Fragile X Syndrome.”

Pediatrics: “Autism Spectrum Disorder in Fragile X Syndrome: Cooccurring Conditions and Current Treatment.”

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