Fragile X Syndrome

What is Fragile X syndrome?

Fragile X syndrome is a genetic disorder usually passed on from a parent to a child at the time the child is conceived. The disorder affects a person’s learning and physical growth.

It also affects behavior and being able to relate to other people. The symptoms of Fragile X syndrome can be mild or moderate. It affects both girls and boys; however, it often has more of an effect on males.

Symptoms of Fragile X syndrome

People who have Fragile X syndrome may have early childhood delays in sitting, crawling, walking, and speech. The delays grow as the child gets older. School-aged children are below grade level in reading, math, and other subjects.

They have behavior problems, social challenges (such as difficulties making eye contact and interacting with others), difficulty learning new things, and focusing.

A person diagnosed with Fragile X syndrome may have certain physical features, as well. These include larger-than-normal ears, jaw, and forehead; a long, narrow face; flat feet; and unusually flexible fingers.

Men who have Fragile X syndrome may have larger-than-normal testicles after puberty. Women may experience infertility and enter menopause earlier than normal. Both men and women diagnosed with Fragile X syndrome can have tremors (shaking) and difficulty with coordination.

What causes Fragile X syndrome?

Fragile X syndrome is caused by a problem with one of your genes. Children inherit genes from their parents. That’s what makes them look like each of their parents. Most of the time, that is how Fragile X syndrome is passed on. However, it is possible to have Fragile X even if a child’s parents don’t have the Fragile X gene.

How is Fragile X syndrome diagnosed?

Some parents notice the delay and see their doctor, which leads to testing. A simple blood test can detect the Fragile X gene in your child anytime after he or she is born. That confirms the diagnosis. If you suspect (or know) either parent has the Fragile X gene, amniocentesis can locate the gene in the baby before it is born. This procedure involves inserting a needle into the mother’s uterus to take a sample of fluid that surrounds the baby. Tests on that fluid can detect the gene.

Can Fragile X syndrome be prevented or avoided?

Since Fragile X syndrome is a genetic disorder, it cannot be prevented or avoided.

Fragile X syndrome treatment

There is no cure for Fragile X syndrome. However, certain therapies can help with the symptoms of the disorder. This includes physical, occupational, and speech therapy. Special education services can help with academic and learning challenges. It also can help with behavior. The earlier a person with Fragile X syndrome receives therapy, the better.

Living with Fragile X syndrome

Living with Fragile X syndrome is similar to living with any type of intellectual disability. Therapies and special education are designed to help the person diagnosed with Fragile X syndrome to be as independent as possible. Independence depends on the severity of the diagnosis. For mild cases, the earlier the person receives therapy, the better their chances of being independent as they become an adult.

Questions to ask your doctor

  • If either parent carries the Fragile X syndrome gene, how likely is it you will pass it on to your child?
  • If I have one child with Fragile X syndrome, am I at a higher risk of having other children with the disease?
  • If I notice delays in my child’s development, how long should I wait before seeing a doctor?
  • Are there any medical conditions associated with Fragile X syndrome (heart, hearing, vision)?

4 Interesting Facts of Fragile X syndrome

  1. X-linked disorder in which individuals are affected by variable intellectual disability; behavioral abnormalities and pervasive developmental disorders (eg, autism) are common 
  2. As with Marfan syndrome, patients typically present with characteristic features that suggest a marfanoid phenotype, such as connective tissue findings (eg, joint laxity, pectus excavatum), characteristic facial features (eg, large head, long face, protruding ears, prominent forehead and chin), tall body habitus, and cardiovascular features (eg, mild dilation of aorta, mitral valve prolapse) 
  3. Differentiated from Marfan syndrome via variations in clinical presentation; patients typically do not present with ophthalmologic abnormalities, and postpubertal males exhibit macro-orchidism
  4. Definitive diagnosis can be made via molecular genetic testing, characterized by presence of loss-of-function mutation in FMR1 (fragile X mental retardation 1) consisting of an increased number of CGG trinucleotide repeats


  1. Centers for Disease Control and Prevention, Facts About Fragile X Syndrome  
  2. National Fragile X Foundation, Fragile X Syndrome  
  3. Genetics Home Reference, U.S. National Library of Medicine, Fragile X Syndrome  

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