Fragile X Syndrome (FAQ)

Answers to questions families often have about caring for their child with fragile X syndrome

What is fragile X syndrome and what causes it?

Fragile X syndrome is a single gene mutation of fragile X messenger ribonucleoprotein 1 (FMR1) on the X chromosome that can be inherited. This genetic difference can cause a spectrum of intellectual disability, autism, and behavioral challenges. While there is not yet a cure, therapies, interventions, and medication can help improve symptoms and behaviors.

What are the symptoms of fragile X syndrome?

The gene mutation that causes fragile x syndrome is found on the X chromosome. Males are usually more affected than females since they have only one X chromosome. Features may include intellectual disabilities, ranging from mild learning disabilities to more severe impairments, ADHD, anxiety, unstable mood, autistic behaviors, sensory integration problems such as hypersensitivity to loud noises 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. They are a long face, large ears, flat feet, hyperextensible joints, and low muscle tone.

How is it diagnosed?

Testing for fragile X syndrome is done by a simple and reliable DNA blood test. This test is widely available, so talk with your doctor. Your pediatrician can order it, but they may refer you to a geneticist or Fragile X specialist for interpretation. Other diagnoses that may be mistaken for Fragile X include Fragile XE syndrome, Klinefelter syndrome, Sotos syndrome, and Prader-Willi syndrome.

What is the prognosis?

Prognosis is a spectrum. People can be mild to severely affected. Things that can help improve outcomes are 1) physical, occupational, speech, and behavioral therapies; 2) medication management; and 3) intrinsic factors. Life expectancy for individuals with fragile X is normal.

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

There is a 50% chance that a child will inherit the affected X chromosome. This should be discussed with your doctor, as the risks can be better estimated with more information about the mother's genetics. Prenatal testing for fragile X is available.

What treatments/therapies/medications are recommended or available?

As of now, there is no cure for fragile X, although appropriate education and medications can help each child reach their potential. Most boys and many girls will continue to show FXS symptoms 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?

A child can have fragile X syndrome and not have autism. About 40% of males and less than 40% of females with fragile X syndrome exhibit significant autistic behaviors. Autistic behaviors include poor eye contact, hand-flapping, self-injurious behavior, and poor sensory skills. See Autism Spectrum Disorder (FAQ).

Why am I being tested for fragile X syndrome when my son 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 tremor/ataxia syndrome. They sometimes receive screening for proactive care of problems that may arise and to give genetic counselors more information to better counsel a family about reproductive risk.


Information & Support

Related Portal Content
Fragile X Syndrome
Assessment and management information for the primary care clinician caring for the child with fragile X syndrome (FXS).
Care Notebook
Medical information in one place with fillable templates to help both families and providers. Choose only the pages needed to keep track of the current health care summary, care team, care plan, health coverage, expenses, scheduling, and legal documents. Available in English and Spanish.

For Parents and Patients

FRAXA Research Foundation
Along with funding research, FRAXA runs scientific meetings, advises pharmaceutical companies, and provides education. Families can reach out to FRAXA for resources, guidance, referrals, and an international community of support.

Fragile X 101 (National Fragile X Foundation)
A nonprofit with the mission of providing unwavering support for every family affected by Fragile X, while relentlessly pursuing a cure.

Fragile X Syndrome / High-Resolution Chromosome Analysis - Letter of Medical Necessity / Preauthorization (PDF Document 119 KB)
A sample of a letter requesting preauthorization for diagnostic testing.


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

Fragile X (
Studies looking at better understanding, diagnosing, and treating this condition; from the National Library of Medicine.

Authors & Reviewers

Initial publication: March 2012; last update/revision: April 2024
Current Authors and Reviewers:
Author: Tyler T Miller, MD
Senior Author: Victoria L. Wilkins, MD
Funding: The Medical Home Portal thanks the 2011-2012 URLEND Medical Home Portal trainees group for their contribution to this page.
Authoring history
2012: first version: Lynne M. Kerr, MD, PhDA
AAuthor; CAContributing Author; SASenior Author; RReviewer