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:
Fragile X-associated tremor/ataxia syndrome (FXTAS). Symptoms include balance problems, shaky hands, unstable mood, memory loss, cognitive problems and numbness in the hands and feet.
Fragile X-associated primary ovarian insufficiency (FXPOI). Symptoms include reduced fertility, infertility, missing or unpredictable menstrual periods and premature menopause.
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:
Normal.
Gray zone.
Premutation carrier.
Full mutation.
Not everyone with the mutated FMR1 gene has FXS symptoms. Some people are still able to make the FMRP protein because:
They’re female. Females are not as likely to get FXS.
The size of the mutation is small.
They have mosaicism. This is where some cells have the FMR1 mutation and others don’t.
What are the symptoms of fragile X syndrome?
Fragile X syndrome affects your child’s intelligence, mental health, physical features and behavior. Common symptoms in each category include:
Intelligence issues:
Learning disabilities.
Low intelligence quotient (IQ). Their IQ scores decrease with age.
Delayed early developmental milestones. Milestones are social/emotional, language/communication, cognitive (thinking, learning, problem-solving) as well as movement/physical development (see below).
Delayed development of nonverbal communication such as using gestures, body language and facial expressions.
Problems with math.
Language processing. You might notice that your child struggles with speech and language around age two.
Talk to your child’s healthcare provider about exactly what milestones to watch out for and how to evaluate them.
Mental health problems:
Anxiety.
Depression.
Obsessive compulsive behaviors.
Physical features:
A long, narrow face.
A large forehead.
A large jaw.
Soft skin.
Large ears and crossed/lazy eyes.
Very flexible or double-jointed fingers.
Flat feet.
Enlarged testicles (in males, after puberty).
A high-arched palate (the roof of the mouth).
Low muscle tone.
Behavior:
Attention-deficit/hyperactivity disorder (ADHD).
Social anxiety, shyness.
Flapping or biting their hands.
Poor eye contact.
Sensory disorders – sensitivity to crowds, touch, sounds, foods and textures.
Difficulty picking up “social cues.”
Sometimes people with fragile X syndrome have other health conditions. In one survey, parents reported that their children also had:
Sleep problems. According to a different study, 4 in 10 people with FXS and autism spectrum disorder have sleeping problems. This is compared to 3 in 10 people who have only FXS.
Aggressiveness or irritability. People with FXS in addition to autism spectrum disorder are more likely to be aggressive.
Self-injury behaviors.
Obesity.
How long does fragile X syndrome last? Is fragile X syndrome curable?
Fragile X is a lifelong syndrome. It can’t be cured.
What are the treatments for fragile X syndrome? What medications are prescribed?
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:
Lithium carbonate.
Gabapentin (Neurontin®).
ADHD:
Methylphenidate (Ritalin®, Concerta®) and Dextroamphetamine (Adderall®, Dexedrine®).
Venlafaxine (Effexor®) and Nefazodone (Serzone®).
Aggression or obsessive-compulsive disorder:
Fluoxetine (Prozac®).
Sertraline (Zoloft®) and Citalopram (Celexa®).
Sleep issues:
Trazodone.
· 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.
How is fragile X syndrome diagnosed? What tests are done?
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:
Amniocentesis: The healthcare provider takes a sample of the amniotic fluid for testing.
Chorionic villus sampling: The healthcare provider takes a sample of cells from the placenta for testing.
At what age are kids usually diagnosed with fragile X syndrome?
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.
Which healthcare providers evaluate and diagnose fragile X syndrome?
Your pediatrician or genetic counselor can order a test for fragile X syndrome.
What questions might a healthcare provider ask to help diagnose fragile X syndrome?
Before your healthcare provider or genetic counselor orders a test for fragile X syndrome, they may ask you the following questions:
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