What Is Fragile X Syndrome (FXS)?

What Is Fragile X Syndrome (FXS)?

Fragile X syndrome is a common type of intellectual disability that affects cognitive function and causes learning deficits in individuals. Fragile X is one form of intellectual disability that also can affect physical appearance, resulting in some recognizable physical characteristics among individuals with fragile X syndrome.

Fragile X syndrome, sometimes referred to as FXS, is a genetic disorder that is caused by changes in a gene called Fragile X Messenger Ribonucleoprotein. The gene FMR1 is supposed to create a protein called FMRP, which aids in brain development. Individuals with fragile X syndrome do not create this FMR protein needed for brain development. There are also associated fragile X disorders in which an individual makes some FMRP, but not an amount consistent with standard protein production.

What Are the Signs & Symptoms of Fragile X Syndrome?

Fragile X is a syndrome that causes cognitive impairment and delays, as well as physical symptoms.

Cognitive Functioning

Many individuals with fragile X will have difficulties with cognitive functioning. These difficulties can range in severity, with some individuals having mild intellectual difficulties, such as learning delays or difficulties with math problems, while others have more severe intellectual deficits, such as learning disabilities or a developmental disability. Cognitive functioning may be affected by fragile X and cause difficulties in the way an individual thinks, learns, or reasons. Sometimes, individuals will suffer from other health problems associated with fragile X, including:

  • Seizures
  • Sleep problems
  • Obesity
  • Self-injury behaviors
  • Aggressiveness or outbursts

Physical Features

Many infants and young children who have fragile X syndrome do not have recognizable physical features associated with FXS, but when children begin to go through puberty, they will often begin to develop physical features that are typical of individuals with FXS. Some of these features include:

  • A narrow face
  • A larger head with large ears and a prominent forehead
  • A large jaw
  • Soft skin
  • Very flexible or double jointed fingers
  • A high-arched palate
  • Low muscle tone

Behavioral, Social & Emotional

Children with fragile X syndrome will generally have some behavioral issues associated with it. They may have difficulty adapting to new situations and may be fearful of a change in routine. Children may have trouble making eye contact with other people, and they also may have anger issues or become aggressive. Attention disorders and hyperactivity are also common among children with FXS, as are anxiety and language processing deficits.

Speech & Language

Children with fragile X will often have difficulty speaking, often leaving out parts of words or stuttering and having difficulty speaking clearly. They may also have trouble understanding others, whether through speech or social cues such as tone of voice or body language. These language symptoms are more common among boys with fragile X; girls typically do not face these difficulties.


Children with fragile X will often have sensory issues, and are bothered by certain sensations such as bright light, loud noises or the way items of clothing may feel on their body. These sensory issues may contribute to acting out and behavior problems for individuals with fragile X.

Fragile X Syndrome Causes

When it comes to the causes of fragile X syndrome, it is due to a spontaneous genetic mutation on the gene called Fragile X Messenger Ribonucleoprotein. This gene will not produce the necessary amount of FMRP to assist in brain development, and thus the symptoms of fragile X will occur due to the lack of this protein. The exact reason behind this genetic mutation is not known. Some parents may carry the permutation for Fragile X Syndrome – the permutation is estimated to be carried by 1 in 148 to 291 women and 1 in 290 to 855 men. Parents who carry the permutation are two times more likely to have a child born with the Fragile X mutation than parents who don’t carry the permutation.

Fragile X Syndrome Treatment

There is no one-size-fits-all treatment for individuals with fragile X, and there is no cure, but there are a variety of treatment options that may work to assist individuals with fragile X in everyday aspects of their lives. There are various education services, therapies, including occupational, developmental, behavioral, and physical, and medications that will allow an individual with fragile X to meet their potential and continue to grow in their abilities and independence. Early intervention is important for individuals with fragile X syndrome; encouraging therapies and treatments early in brain development helps children learn valuable skills early on.

How Common Is Fragile X Syndrome?

There is no exact count for the number of individuals with fragile X syndrome worldwide, but researchers have estimated that the number of children born with fragile X syndrome is around 1 in 11,000 for girls and 1 in 7,000 for boys. Boys have a greater chance of being diagnosed with fragile X syndrome, and boys generally have more severe symptoms than their female peers who have fragile X syndrome.

What To Do if You Think Your Child May Have Fragile X Syndrome

If you think your child may have fragile X syndrome, it is important to speak with your doctor to discuss fragile X syndrome diagnosis and treatment options. Your doctor can refer you to a specialist who will provide guidance and knowledge on symptoms and treatments. Early intervention is important for children with fragile X syndrome, so if you think your child may have fragile X, speaking with a doctor soon is a great course of action. There may be various community groups and treatment centers where you can become connected with other parents of children with fragile X syndrome, and where your child can connect with their peers with fragile X. These are great places to learn about options and treatments to help your child thrive.

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