Fragile X Syndrome Information

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By Disabled World - 2008-11-02
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What is Fragil X Syndrome?

Fragile X syndrome is the second most common identifiable cause of genetic mental retardation after Down syndrome.

The fragile X syndrome is a genetic disorder caused by mutation of the FMR1 gene on the X chromosome. Mutation at that site is found in 1 out of about every 2000 males and 1 out of about every 259 females. (Incidence of the disease itself is about 1 in every 4000 females.)

Because males normally have only one copy of the X chromosome, those males with significant trinucleotide expansion at the FMR1 locus are symptomatic. They are intellectually disabled and may show various physical features of the fragile X syndrome.

Females have two X chromosomes and thus have double the chance of having a working FMR1 allele. Females carrying one X chromosome with an expanded FMR1 gene can have some signs and symptoms of the disorder or be normal. Although the extra X chromosome can serve as a backup, only one X chromosome is active at a time due to X-inactivation.

Females carrying one copy of the fragile X can transmit it to their sons or daughters; in this case each child has a 50% chance of inheriting the fragile X. Sons who receive the fragile X are at high risk of intellectual disability. Daughters who receive the fragile X may appear normal or they may be intellectually disabled, usually to a lesser degree than boys with the syndrome.

Fragile X includes:

Fragile X syndrome (FXS) - This impairment can range from learning disabilities to more severe cognitive or intellectual disabilities. FXS is the most common known cause of autism or "autistic-like" behaviors. Symptoms also can include characteristic physical and behavioral features and delays in speech and language development.

Fragile X-associated tremor/ataxia syndrome (FXTAS) - A condition which affects balance, tremor and memory in some older male gene carriers.

Fragile X-associated primary ovarian insufficiency (FXPOI) - A problem with ovarian function which can lead to infertility and early menopause in some female gene carriers.

Characteristics of Fragile X Syndrome

Aside from intellectual disability, prominent characteristics of the syndrome include an elongated face, large or protruding ears, flat feet, larger testicles in men (macroorchidism), and low muscle tone.

Speech may include cluttered speech or nervous speech.

Behavioral characteristics may include stereotypic movements (e.g., hand-flapping) and atypical social development, particularly shyness and limited eye contact.

Some individuals with the fragile X syndrome also meet the diagnostic criteria for autism.

Most females experience symptoms to a lesser degree because of their second X-chromosome, however they can develop just as severe symptoms.

While full mutation males tend to present with severe intellectual disability, the symptoms of full mutation females run the gamut of minimally affected to severe intellectual disability, which may explain why females are underdiagnosed relative to males.

Seizures (epilepsy) affect about 25% of people with fragile X.

Treatment of Fragile X Syndrome

There is no cure for Fragile X, but there are ways to help with the symptoms.

Standard treatment includes special education, speech, occupational, and sensory integration training; and behavior modification programs. Surgical correction of heart defects is sometimes necessary. Genetic counseling will benefit families of affected persons. Other treatment is symptomatic and supportive.

UPDATE: Recently researchers working with mice have significantly alleviated a wide range of abnormalities due to fragile X syndrome by altering only a single gene, countering the effects of the fragile X mutation. They said their achievement offers the potential for treatment of the disorder, the most common form of inherited mental retardation and a leading identified genetic cause of autism.

For more information about Fragile X syndrome

NICHD Information Resource Center

P.O. Box 3006
Rockville, MD 20847
Phone: 1-800-370-2943
Fax: 301-984-1473
E-mail: NICHDIRC@ mail.nih.gov

The Vanderbilt Fragile X Clinic is a clinic that provides resources for individuals and families affected by fragile X.

The clinic is part of the National Fragile X Foundation Clinics Consortium.

Center for Child Development
Monroe Carell Jr. Children's Hospital at Vanderbilt
Doctors' Office Tower (DOT), 9th Floor
Nashville, TN 37232

Phone: 615.936.0249
Fax: 615.936.0256

The Fragile X Association of Australia (www.fragilex.org.au) is a non-profit organisation made up of family, friends, therapists, doctors and carers of people with Fragile X Syndrome.

Their aim is to help people with Fragile X realise their full potential, provide information and support to those people whose lives have been affected by Fragile X, and promote acceptance and integration of people with Fragile X into the community.