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Fragile X Syndrome


Nina N. Powell-Hamilton

, MD, Sidney Kimmel Medical College at Thomas Jefferson University

Last full review/revision Jul 2020

Fragile X syndrome is a genetic abnormality on the X chromosome that leads to intellectual disability and behavior problems.

The symptoms of Fragile X syndrome are caused by an abnormality of a specific gene on the X chromosome (see Gene abnormalities Gene abnormalities Chromosomes are structures within cells that contain a person's genes. A gene is a segment of deoxyribonucleic acid (DNA) and contains the code for a specific protein that functions in one or... read more ). People have an excessive number of copies (more than 200) of a small segment of deoxyribonucleic acid (DNA). People with 55 to 200 extra copies are considered to have a premutation because, although they do not have the disorder, their offspring are at greater risk of having it.

Symptoms of Fragile X Syndrome

Children and adults with the syndrome may have physical, intellectual, and behavior problems. Features, which are often subtle, include delayed development; large, protruding ears; a prominent chin and forehead; and, in boys, large testes (most apparent after puberty). The joints may be abnormally flexible, and heart disease (mitral valve prolapse Mitral Valve Prolapse (MVP) Mitral valve prolapse is a disorder in which the valve flaps (cusps) bulge into the left atrium when the left ventricle contracts, sometimes allowing leakage (regurgitation) of blood into the... read more Mitral Valve Prolapse (MVP) ) may occur.

Children may have mild to moderate intellectual disability. Features of autism Autism Spectrum Disorders Autism spectrum disorders are conditions in which people have difficulty developing normal social relationships, use language abnormally or not at all, and show restricted or repetitive behaviors... read more may develop, including repetitious speech and behavior, poor eye contact, and social anxiety.

Diagnosis of Fragile X Syndrome

  • DNA tests

Fragile X syndrome can be detected by DNA tests done after birth. The diagnosis of Fragile X syndrome is typically made when the child is school age or an adolescent. Boys with autism and intellectual disability should be tested for Fragile X syndrome, especially if their mother has relatives who have similar problems.

Treatment of Fragile X Syndrome

  • Speech, language, and occupational therapies

  • Sometimes drugs

Early intervention, including speech and language therapy and occupational therapy, can help children with Fragile X syndrome maximize their abilities.

Stimulants, antidepressants, and antianxiety drugs may be beneficial for some children.

More Information about Fragile X Syndrome

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

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Preventive Health Care Visits in Infants
Frequent doctor visits are recommended for all infants younger than 1 year of age. These visits, also called well-child visits, make it possible to check development, look for health problems, provide age-appropriate vaccinations, and educate parents. Which of the following is a condition that might affect some infants born very prematurely, with less than 32 weeks of development in the uterus?
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