Fragile X syndrome is the leading cause of inherited intellectual disabilities like autism. There are behavioral, physical, intellectual and mental health symptoms. Females have milder symptoms than males. FXS is not life-threatening and although there is no cure, medication and therapy can help manage the symptoms.
Fragile X syndrome (FXS), also known as Martin-Bell syndrome, is an inherited condition that causes developmental delays, intellectual disabilities, learning and behavioral issues, physical abnormalities, anxiety, attention-deficit/hyperactivity disorder and/or autism spectrum disorder, among other problems. It’s the most common form of inherited intellectual and developmental disability (IDD).
FXS is named fragile X syndrome because, when looked at through a microscope, part of the X chromosome looks “broken” or “fragile.”
FXS is one of three syndromes in the fragile X family. The other two syndromes are:
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
No. The symptoms of fragile X syndrome are not life-threatening.
Although the exact number isn’t clear, researchers estimate that, worldwide, about 1 in 8,000 to 11,000 females and 1 in 4,000 to 7,000 males have fragile X syndrome.
Experts don’t know for sure how many people carry the fragile X premutation, which can be passed down to their child and cause fragile X. Some studies estimate that, in the United States, 1 in 148 to 291 women and 1 in 290 to 855 men have the premutation. Parents with the premutation are nearly two times more likely to have a child with a disability than those without the premutation.
Fragile x syndrome can sometimes cause autism. If your child has autism, they have a 2% to 6% chance of also having fragile X syndrome.
Yes, fragile X syndrome is an inherited genetic condition.
No, but males are more likely to have fragile X syndrome than females. Their symptoms are also more severe.
Yes. If your child has fragile X syndrome, you should tell your primary healthcare provider. As a possible carrier, you’re at a higher risk for:
Menopause that starts before age 40 (females only).
Fragile X syndrome gets passed from parent to child. A DNA part called the “CGG triplet repeat” expands within a gene called “FMR1,” producing a mutation that causes fragile X syndrome. A normal part repeats five to 40 times, but in people with fragile X syndrome it repeats more than 200 times. This “silences” the FMR1 gene, which messes up the nervous system and causes the symptoms of fragile X syndrome.
There are four classifications of the fragile X mutation. They’re determined by the number of times the CGG repeats in the DNA:
Not everyone with the mutated FMR1 gene has FXS symptoms. Some people are still able to make the FMRP protein because:
Fragile X syndrome affects your child’s intelligence, mental health, physical features and behavior. Common symptoms in each category include:
Intelligence issues:
Talk to your child’s healthcare provider about exactly what milestones to watch out for and how to evaluate them.
Mental health problems:
Physical features:
Behavior:
Sometimes people with fragile X syndrome have other health conditions. In one survey, parents reported that their children also had:
Fragile X is a lifelong syndrome. It can’t be cured.
Diagnosing fragile X syndrome requires DNA from blood, amniotic fluid or other tissues. Your healthcare provider will send the sample to a laboratory that will determine if your child has the FMR1 gene.
If you’re pregnant and concerned that your child has fragile X syndrome, you can see a genetic counselor where you may undergo the following prenatal tests:
Boys are usually diagnosed around 35 to 37 months old, and girls around 42 months. You might start to notice symptoms in your child as early as 12 months.
Your pediatrician or genetic counselor can order a test for fragile X syndrome.
Before your healthcare provider or genetic counselor orders a test for fragile X syndrome, they may ask you the following questions:
Fragile X syndrome can’t be cured, but the symptoms can be treated. Your child’s healthcare provider may prescribe a variety of medications, but therapy should also be included – therapy that works with coping and behavioral skills.
Examples of medications, categorized by symptom, include:
Seizures or mood instability:
ADHD:
Aggression or obsessive-compulsive disorder:
Sleep issues:
· Melatonin.
This is just a short list of possible medications your child’s healthcare provider may prescribe. Talk to the provider about possible side effects and complications that may come with each medication.
No, fragile X syndrome can’t be prevented.
Unfortunately there isn’t anything you can do to reduce your child’s risk of fragile X syndrome. If you have the FMR1 gene, they could, too.
Some individuals with fragile X syndrome are able to live independently. Surveys show that around 4 in 10 women and 1 in 10 men with fragile X syndrome grow up to have a high level of independence. Women more than men have the following abilities:
Women with FXS thrive more than men. Women, specifically 8 out of 20 women, don’t need help with daily activities – neither do 1 in 20 men. Most women get a high school diploma but a majority of men don’t. Nearly half of women with FXS have full-time jobs but only 2 in 10 men.
Yes. It’s a lifelong syndrome.
Your child may need special accommodations at daycare or school. Some parts of the school day and classroom may need to be adjusted to fit their needs. Your child’s teacher might be able to make environmental adjustments and curricular adjustments.
Environmental adjustments:
Curricular adjustments:
Be sure to inform your child’s school that they have fragile X syndrome. Have a conversation with their teacher about their unique needs. You may also meet with a school psychologist and/or counselor. They work with children three years old and older. Other healthcare providers you may want to connect with are occupational therapists, behavior therapists and speech and language therapists. Talk with your local school and healthcare providers for referrals.
It’s important to note that there are many positive characteristics of people with fragile X syndrome. For example, researchers have noted that they’re:
The intelligent quotient (IQ) of a person with fragile X syndrome decreases over time. They become less intelligent with age.
None of the symptoms of fragile X syndrome are life-threatening, so the life expectancy for someone with fragile X syndrome is the same as for the average person.
How do I help my friend or family member with fragile X syndrome?
Educate yourself as much as possible. Look for support groups and community resources that can help you and them. Life skills programs may be appropriate. Some provide guidance about:
Take your child in to see their pediatrician as soon as you notice the symptoms of fragile X syndrome. Don’t wait, as early intervention is important.
The following are some questions you may want to ask the healthcare provider when you discuss your child’s diagnosis:
A note from Cleveland Clinic
Fragile X syndrome can be a difficult diagnosis for the child’s family and friends. It’s the start of a lot of change and adjustment. Therapy, medications and accommodations at school are now part of your child’s life. While helping your child with their issues, be sure not to neglect your own needs. Remember that if your child has fragile X syndrome, that means you’re more vulnerable to dementia, depression, migraines, chronic pain, premature menopause, high blood pressure, anxiety, hypothyroidism and sleep apnea. Don’t neglect your own care!
Last reviewed by a Cleveland Clinic medical professional on 05/18/2021.
Learn more about our editorial process.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy