Fragile X syndrome
Fragile X syndrome is a condition that happens when the body can’t make enough of a protein it needs for the brain to grow and develop. Fragile X can cause problems with learning and behavior.
Fragile X syndrome is the most common inherited cause of learning problems and intellectual disabilities. In the United States, about 1 in 4,000 boys and 1 in 8,000 girls are born each year with fragile X. Usually, boys with fragile X have more serious learning and behavior problems than girls.
What causes fragile X syndrome?
Fragile X syndrome is inherited. This means it’s passed from parent to child through genes. A gene is a part of your body’s cells that stores instructions for the way your body grows and works. Genes are stored in structures called chromosomes. Everyone has 23 pairs of chromosomes, or 46 in all. For each pair, you get one chromosome from your mother and one from your father.
Sometimes the instructions in genes change. This is called a gene change or a mutation. Parents can pass gene changes to their children. Sometimes a gene change can cause a gene to not work correctly. Sometimes it can cause birth defects or other health conditions. A birth defect is a health condition that is present in a baby at birth.
One set of chromosomes is responsible for your gender. This set is made up of X and Y chromosomes. Girls have two X chromosomes (XX). Boys have an X and a Y chromosome (XY). Fragile X syndrome is caused when part of gene repeats more than usual on the X chromosome. Everyone has at least one X chromosome. If a girl has fragile X, her second X chromosome usually is healthy. But boys with fragile X don’t have a second healthy X chromosome. This is why symptoms of fragile X syndrome usually are more serious in boys than in girls.
You can have the fragile X gene change and not have clear signs of the condition. When this happens, you’re called a carrier, and the condition is called fragile X premutation. If either you or your partner is a carrier, you can pass fragile X to your baby.
You may be a permutation carrier if you have ovarian insufficiency or fragile X-associated tremor/ataxia syndrome (also called FXTAS). Ovarian insufficiency, sometimes called early menopause, is when your ovaries don’t work correctly or at all at an early age (less than 40 years). FXTAS is a condition that affects your ability to think and move. It usually affects men older than 50, but women can have it.
How can you find out if you’re a fragile X carrier?
Before or during pregnancy, you and your partner may want to have a genetic test called carrier screening to find out if you’re a fragile X carrier. Anyone can have the test. But it may be more important if you:
- Have autism or autism-like behaviors. Autism is a group of disorders that affect a person’s speech, social skills and behavior. About 1/3 of males with Fragile X have autism features that affect social skills and behavior. Fragile X is the most common known genetic cause of autism.
- Had an unexplained intellectual disability or developmental delay as a child. Unexplained means there’s no known cause (like a head injury) for the disability or delay. A developmental delay is when a child’s skills in movement, learning, thinking, language and behavior develop later than most children’s.
- Have a family history of fragile X syndrome, ovarian insufficiency, autism or unexplained intellectual disability or developmental delay. Family history means that someone in your family has had one of these conditions.
- Have a partner who is a fragile X carrier
If you’re thinking about having carrier screening, you may want to see a genetic counselor. This is a person who is trained to help you understand about how genes, birth defects and other medical conditions run in families, and how they can affect your health and your baby’s health. Ask your health care provider if you need help finding a genetic counselor. Or contact the National Society of Genetic Counselors.
Can you find out if your baby has fragile X syndrome before birth?
Yes. If you or your partner is a carrier, you can talk to your health care provider about prenatal tests called amniocentesis and chorionic villus sampling (also called CVS). These tests can help you find out the chances of having a baby with fragile X.
How do you know if your baby has fragile X after he’s born?
Signs and symptoms of fragile X can be mild or serious. At first, the only sign or symptom you may notice in your baby is a large head. But as he grows, common signs and symptoms can include:
Developmental signs and symptoms
- Learning problems, especially for boys
- Developmental delays in sitting, crawling or walking
- Problems with speech and language, especially for boys
Social or behavior signs and symptoms
- Not making eye contact
- Having trouble paying attention
- Flapping hands
- Being hyperactive
- Being afraid in new situations
- Being aggressive for boys
- Being very shy for girls
- Being bothered by certain sensations, such as bright light, loud noises or the way something feels
- Not wanting to be touched
Physical signs and symptoms
- Long face, ears and chin
- Loose, flexible jointsFlat feet
- Large testicles after puberty for boys
- Seizures in about 15 out of 100 boys (15 percent) and 5 out of 100 girls (5 percent)
If your baby has any of these signs or symptoms, or if you have a family history of fragile X or premutation, tell your baby’s health care provider. Your baby can get a blood test for fragile X.
Boys with fragile X syndrome usually are diagnosed at around age 3. Because girls have less serious symptoms, they’re usually diagnosed a little later, around age 3½.
How is fragile X syndrome treated?
There is no cure for fragile X syndrome. But children with the condition can do well when they get treatment starting in early childhood. They may need help learning to talk, walk and interact with others.
Certain medicines can help some children with behavioral symptoms be better able to learn, including:
- Medicines used to treat depression and anxiety and other mental health problems
- Stimulants like Ritalin®, which often are used to treat attention deficit hyperactivity disorder (also called ADHD)
- Medicines used to help prevent seizures
For more information
Centers for Disease Control (CDC)
CDC video on Fragile X
The National Fragile X Foundation
Last Reviewed January 2014
Frequently Asked Questions
Can dad's exposure to chemicals harm his future kids?
Dad's exposure to harmful chemicals and substances before conception or during his partner's pregnancy can affect his children. Harmful exposures can include drugs (prescription, over-the-counter and illegal drugs), alcohol, cigarettes, cigarette smoke, chemotherapy and radiation. They also include exposure to lead, mercury and pesticides.
Unlike mom's exposures, dad's exposures do not appear to cause birth defects. They can, however, damage a man's sperm quality, causing fertility problems and miscarriage. Some exposures may cause genetic changes in sperm that may increase the risk of childhood cancer. Cancer treatments, like chemotherapy and radiation, can seriously alter sperm, at least for a few months post treatment. Some men choose to bank their sperm to preserve its integrity before they receive treatment. If you have a question about a specific exposure, contact the Organization of Teratology Information Specialists at www.otispregnancy.org.
Can Rh factor affect my baby?
The Rh factor may be a problem if mom is Rh-negative but dad is Rh-positive. If dad is Rh-negative, there is no risk.
If your baby gets her Rh-positive factor from dad, your body may believe that your baby's red blood cells are foreign elements attacking you. Your body may make antibodies to fight them. This is called sensitization.
If you're Rh-negative, you can get shots of Rh immune globulin (RhIg) to stop your body from attacking your baby. It's best to get these shots at 28 weeks of pregnancy and again within 72 hours of giving birth if a blood test shows that your baby is Rh-positive. You won't need anymore shots after giving birth if your baby is Rh-negative. You should also get a shot after certain pregnancy exams like an amniocentesis, a chorionic villus sampling or an external cephalic version (when your provider tries to turn a breech-position baby head down before labor). You'll also want to get the shot if you have a miscarriage, an ectopic pregnancy or suffer abdominal trauma.
Does cleft lip or cleft palate cause dental problems?
A cleft lip or cleft palate that extends into the upper gums (where top teeth develop) can cause your baby to have certain dental problems, including:
- Missing teeth
- Too many teeth
- Oddly shaped teeth
- Teeth that are out of position around the cleft
Every baby with a cleft lip or palate should get regular dental checkups by a dentist with experience taking care of children with oral clefts. Dental problems caused by cleft lip or palate usually can be fixed. If needed, your baby can get ongoing care by a team of experts, including:
- A dentist
- An orthodontist to move teeth using braces
- An oral surgeon to reposition parts of the upper jaw, if needed, and to fix the cleft
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause ear problems?
Cleft lip does not cause ear problems.
Babies with cleft palate, however, are more likely than other babies to have ear infections and, in some cases, hearing loss. This is because cleft palate can cause fluid to build up in your baby’s middle ear. The fluid can become infected and cause fever and earache. If fluid keeps building up with or without infection, it can cause mild to moderate hearing loss.
Without treatment , hearing loss can affect your baby’s language development and may become permanent.
With the right care, this kind of hearing loss is usually temporary. Your baby’s provider may recommend:
- Having your baby’s ears checked regularly for fluid buildup
- Medicines for treating fluid buildup and ear infections
- Ear tubes if your baby has fluid in his ears over and over again. Ear tubes are tiny tubes that are inserted into the eardrum to drain the fluid and help prevent infections.
See also: Cleft lip and cleft palate
Does cleft lip or cleft palate cause problems with breastfeeding?
Babies with only a cleft lip usually don’t have trouble breastfeeding. Most of the time, they can breastfeed just fine. But they may need some extra time to get started.
Babies with cleft lip and palate or with isolated cleft palate can have:
- Trouble sucking strong enough to draw milk through a nipple
- Problems with gagging or choking
- Problems with milk coming through the nose while feeding
Most babies with cleft palate can’t feed from the breast. If your baby has cleft palate, he can still get the health benefits of breastfeeding if you feed him breast milk from a bottle. Your provider can show you how to express (pump) milk from your breasts and store breast milk.
Your baby’s provider can help you start good breastfeeding habits right after your baby is born. She may recommend:
- Special nipples and bottles that can make feeding breast milk from a bottle easier
- An obturator. This is a small plastic plate that fits into the roof of your baby’s mouth and covers the cleft opening during feeding.
See also: Cleft lip and cleft palate, Breastfeeding
Does cleft lip or cleft palate cause speech problems?
Children with cleft lip generally have normal speech. Children with cleft lip and palate or isolated cleft palate may:
- Develop speech more slowly
- Have a nasal sound when speaking
- Have trouble making certain sounds
Most children can develop normal speech after having cleft palate repair. However, some children may need speech therapy to help develop normal speech.
See also: Cleft lip and cleft palate
What are choroid plexus cysts?
The choroid plexus is the area of the brain that produces the fluid that surrounds the brain and spinal cord. This is not an area of the brain that involves learning or thinking. Occasionally, one or more cysts can form in the choroid plexus. These cysts are made of blood vessels and tissue. They do not cause intellectual disabilities or learning problems. Using ultrasound, a health care provider can see these cysts in about 1 in 120 pregnancies at 15 to 20 weeks gestation. Most disappear during pregnancy or within several months after birth and are no risk to the baby. They aren't a problem by themselves. But if screening tests show other signs of risk, they may indicate a possible genetic defect. In this case, testing with higher-level ultrasound and/or amniocentesis may be recommended to confirm or rule out serious problems.
What if I didn't take folic acid before pregnancy?
If you didn’t take folic acid before getting pregnant, it doesn't necessarily mean that your baby will be born with birth defects. If women of childbearing age take 400 micrograms of folic acid every day before and during early pregnancy, it may help reduce their baby’s risk for birth defects of the brain and spin called neural tube defects (NTDs). But it only works if you take it before getting pregnant and during the first few weeks of pregnancy, often before you may even know you’re pregnant.
Because nearly half of all pregnancies in the United States are unplanned, it's important that all women of childbearing age (even if they're not trying to get pregnant) get at least 400 micrograms of folic acid every day. Take a multivitamin with folic acid before pregnancy. During pregnancy, switch to a prenatal vitamin, which should have 600 micrograms of folic acid.
Last reviewed November 2012