Fragile X Syndrome


Here you’ll find answers to some of the questions that parents often have about this condition. Additional resources are listed at the bottom of the page. Diagnosis and management information can be found in the Fragile X Syndrome module, which is written for primary care clinicians but also may be of help to parents and family members.

What is fragile X syndrome and what causes it?

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disabilities and a common known cause of autism. It may not be immediately apparent that a person has fragile X syndrome as symptoms, such as learning problems, autism, and anxiety, and some physical features, can be subtle.

What are the symptoms of fragile X syndrome?

Males are usually more affected than females. Features may include: intellectual disabilities, ranging from mild learning disabilities to intellectual disability, attention deficit and hyperactivity, anxiety and unstable mood, autistic behaviors and/or sensory integration problems, such as hypersensitivity to loud noices or bright lights, speech delay, with expressive language more severely affected than receptive language, and seizures. Physical features are usually hard to recognize in babies and young children, but sometimes become more apparent with age: long face, large ears, flat feet, hyperextensible joints, low muscle tone, and in adult men, large testes.

How is it diagnosed?

Testing for fragile X is done by a simple and reliable DNA blood test. This test is widely available, so talk with your doctor.

What is the prognosis?

Prognosis will depend on your child's symptoms now. Children who are mildly affected at diagnosis may be less affected as adults than children with severe symptoms at diagnosis.

What is the risk for other family members or future babies?

Fragile X syndrome occurs when there is an expansion of the genetic material in a specific place on the X chromosome. The chances of having a second child with fragile X increase if the mother has a larger expansion, and can be as high as 50% if the second child is male. This should be discussed with your doctor as the risks can be better estimated with more information about the mother's genetic material. Prenatal testing for fragile X is available.

What treatments/therapies/medications are recommended or available?

There is currently no cure for fragile X, although appropriate education and medications can help maximize the potential of each child. However, most boys and many girls remain significantly affected throughout their lives.

I have been told that my child has fragile X syndrome (FXS), but he has no signs of autism. Could the doctors be wrong?

Only about 20% of children with fragile X syndrome exhibit significant autistic behaviors, so it is very possible for a child to have fragile X syndrome and not have autism. Autistic behaviors include poor eye contact, hand-flapping, self-injurious behavior, and poor sensory skills.

Why am I being tested for fragile X syndrome; it is my son who has the disorder?

Extended family members of individuals with fragile X syndrome may have related disorders, including social problems, learning disabilities, premature ovarian failure, and fragile X-associated trem/ataxia syndrome, depending on gene status. Screening is sometimes done on extended family members to provide proactive care for problems that may arise as well as to give genetic counselors more information so that they may better counsel a family regarding recurrence risk.


Information & Support

Where can I go for further information?

For Parents and Patients

Fragile X syndrome (MedLinePlus)
Introduction and links to a variety of reliable sources of information about FXS, from the National Library of Medicine and National Institutes of Health.

FRAXA - The Fragile X Research Association
Information from FRAXA regarding the diagnosis of and research in fragile X syndrome

National Fragile X Foundation
A non-profit organization run by parents of children with fragile X syndrome. This organization supports research into finding a cure for fragile X syndrome and supports families with children with fragile X syndrome.


Behavioral Programs

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Developmental Pediatrics

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Early Intervention Programs

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Genetics, Prenatal

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Pediatric Cardiology

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Pediatric Genetic Counseling

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Pediatric Genetics

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Pediatric Neurology

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Pediatric Ophthalmology

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Pediatric Orthopedics

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Pediatric Physical Medicine & Rehab

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Psychiatrist, Child-18

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Psychologist, Child-18

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Swallow Studies

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For other services related to this condition, browse our Services categories or search our database.


Clinical trials in Fragile X (
Listing of current and recent studies related to Fragile X.

Fenobam study information (FRAXA)
Although in the early stages, fenobam, a slective mGluR5 antagonist, may be helpful in individuals with fragile X syndrome. So far, it has been tested only in adults.


Author: Lynne M Kerr, MD, PhD - 3/2012
Compiled and edited by: URLEND Trainees, 2011-2012 - 3/2012
Content Last Updated: 9/2015


The Medical Home Portal thanks the 2011-2012 URLEND Medical Home Portal trainees group for their contribution to this page.