What Is Fragile X Syndrome?

Fragile X Syndrome

Image source: Fragilex.org.uk

Fragile X syndrome is a genetic disorder. It is the most common cause of inherited intellectual disability in boys, however girls can also inherit the condition. According to the National Fragile X Foundation, it is also the most common genetic cause of autism. The symptoms of Fragile X can range from mild to severe. While there is no cure for this disorder, treatments are available to address the symptoms.


Fragile X is inherited. However, a child may inherit the condition even if neither of the parents have it. Fragile X is caused by a mutation on the fragile area of the X chromosome. The specific gene affected is FMR1. The mutation occurs when a portion of the gene code is improperly repeated. It may be repeated many times, in which case the risk of developing Fragile X increases.

The exact science of inheriting the condition is a bit complicated (check this website for the in-depth, scientific explanation), but essentially, a child may inherit a premutation or a full mutation. If a person has a premutation, they may pass the condition on to future generations, and they may also develop Fragile X-associated disorders. A child with a full mutation will typically experience Fragile X symptoms of varying degrees.

DNA Testing

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Signs & Symptoms

Fragile X syndrome can cause a wide range of symptoms. It can cause mild to severe intellectual disabilities and speech and language problems. Typically, most boys who have Fragile X will have speech and language difficulties. Communication problems are less common in girls who inherit the condition. Some of the speech and language signs can include repetitive sounds, words, and phrases, as well as cluttered speaking. Fragile X may also cause social or behavioral issues. Children may shy away from transitions or new situations. Boys in particular may exhibit aggression or poor attention span, while girls tend to be quite shy.

Fragile X often causes sensory issues. Children might be bothered by excessive stimulation, like loud noises or bright lights. They may not like to be touched or they may avoid eye contact. Physical symptoms, such as a long face and ears, are also possible. Children may also have low muscle tone, extremely flexible joints, and flat feet.


Diagnosing Fragile X can be tricky – not because it’s difficult to run the tests, but because there may be few outward signs present at birth. There may be very subtle differences in facial features and a larger head circumference. If Fragile X is not diagnosed at birth, it may take a while for parents to notice signs of mental retardation. The most accurate diagnostic test for this condition is DNA testing. However, the doctor may run other tests, such as a protein test, to check for the possibility of Fragile X before confirming it with a DNA test.

Occupational Therapist Working with Child

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Treatment Options

While there is no cure for Fragile X syndrome, treatment options are available. If your child exhibits speech and language difficulties, a speech-language pathologist (SLP) can develop a treatment plan to address those issues. A physical therapist and an occupational therapist can address physical signs and symptoms, while a behavioral therapist can teach your child to cope with distress.

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