Home > Diseases and Conditions > Fragile X syndrome
  • We are sorry, but NCBI web applications do not support your browser and may not function properly. More information

PubMed Health. A service of the National Library of Medicine, National Institutes of Health.

A.D.A.M. Medical Encyclopedia [Internet]. Atlanta (GA): A.D.A.M.; 2013.

A.D.A.M. Medical Encyclopedia [Internet].

Fragile X syndrome

Martin-Bell syndrome; Marker X syndrome

Last reviewed: September 8, 2013.

Fragile X syndrome is a genetic condition involving changes in part of the X chromosome. It is the most common form of inherited intellectual disability in boys.

Causes

Fragile X syndrome is caused by a change in a gene called FMR1. A small part of the gene code is repeated on a fragile area of the X chromosome. The more repeats, the more likely the condition will occur.

The FMR1 gene makes a protein needed for your brain to function properly. A defect in the gene makes your body produce too little of the protein, or none at all.

Boys and girls can both be affected, but because boys have only one X chromosome, a single fragile X is likely to affect them more severely. You can have fragile X syndrome even if your parents do not have it.

A family history of fragile X syndrome, developmental problems, or intellectual disability may not be present.

Symptoms

Behavior problems associated with fragile X syndrome include:

  • Autism spectrum disorder
  • Delay in crawling, walking, or twisting
  • Hand clapping or hand biting
  • Hyperactive or impulsive behavior
  • Intellectual disability
  • Tendency to avoid eye contact

Physical signs may include:

  • Flat feet
  • Flexible joints and low muscle tone
  • Large body size
  • Large forehead or ears with a prominent jaw
  • Long face
  • Soft skin

Some of these problems are present at birth, while others may not develop until after puberty.

Family members who have fewer repeats in the FMR1 gene may not have intellectual disability. Women may have premature menopause or difficulty becoming pregnant. Both men and women may have problems with tremors and poor coordination.

Exams and Tests

There are very few outward signs of Fragile X syndrome in babies. Some signs may include:

  • Large head circumference in babies
  • Intellectual disability
  • Large testicles after the start of puberty
  • Subtle differences in face features

In females, excess shyness may be the only sign of the disorder.

Genetic testing can diagnose this disease.

Treatment

There is no specific treatment for Fragile X syndrome. Instead, training and education have been developed to help affected children function at the highest possible level.

Support Groups

National Fragile X Foundation -- www.fragilex.org

Outlook (Prognosis)

How well the patient does depends on the amount of intellectual disability.

Possible Complications

Complications vary depending on the type and severity of symptoms.

  • Recurrent infections in children
  • Seizure disorder

Fragile X syndrome can be a cause of autism or related disorders, although not all children with fragile X syndrome have these conditions.

Prevention

Genetic counseling may be helpful if you have a family history of this syndrome and are planning to become pregnant.

References

  1. Shapiro BK, Batshaw ML. Intellectual disability. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 33.

Review Date: 9/8/2013.

Reviewed by: Chad Haldeman-Englert, MD, FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only — they do not constitute endorsementscof those other sites. © 1997–2011 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Copyright © 2013, A.D.A.M., Inc.

What works?

  • Folic acid for fragile X syndromeFolic acid for fragile X syndrome
    People with fragile X syndrome (or FXS) have intellectual limitations that can range from mild to severe. Fragile X syndrome is considered the most common form of inherited intellectual disability and it has been estimated that it affects approximately 1 in 4000 males and 1 in 8000 females. Folate is particularly important during the early development of the brain and in later life is involved in methylation processes that are essential for the maintenance of normal brain function. It was observed that cells from patients with fragile X syndrome cultured in solutions deficient in folic acid revealed a fragile site at the X chromosome; consequently it was thought that individuals with fragile X syndrome had low folate levels in their bodies, which may be due to insufficient dietary intake, inefficient absorption or impaired metabolic utilisation. It was argued that supplementing their dietary intake might help improve the adverse developmental and behavioural effects of the condition.
See all (3) ...

PubMed Health Blog...

read all...

Read More

MedlinePlus.gov links to free, reliable, up-to-date health information from the National Institutes of Health (NIH) and other trusted health organizations.

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...