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Fragile X Syndrome


Fragile X syndrome is the most common genetically-inherited form of mental retardation currently known. Fragile X exhibits X-linkage , which means that the frequency of the syndrome is greater in males than in females. The observable characteristics of Fragile X occur in approximately 1 in 1,000 male births and 1 in 2,500 female births. Because of scientific advances, improvements in genetic testing, and increased awareness, the number of children diagnosed with Fragile X has increased significantly over the last decade. In 1991 the FMR-1 ( Fragile X mental retardation ) gene was discovered.

Symptoms and Signs

Individuals with Fragile X may have a cluster of physical, behavioral, mental, and other characteristics. These symptoms may vary in number and degree among affected children. Children with Fragile X often appear normal in infancy but develop typical physical characteristics during their lifetime.

Males with Fragile X have some common physical characteristics : a long narrow face; large or prominent ears; and macroorchidism (enlarged testicles). Females with Fragile X syndrome do not exhibit most of the physical characteristics found in males with Fragile X, although they often have large or prominent ears.

The most prevalent behavioral characteristics of children with Fragile X are attention problems and hyperactivity, known as attention-deficit hyperactivity disorder (ADHD). Some of the other behaviors associated with Fragile X are similar to those of autism . However, one strength of males with Fragile X is their great sociability and friendliness, in contrast to autistic children, who appear unable to relate to others.

Mental retardation associated with Fragile X is similar to that of Down syndrome in that most of those affected fall somewhere in the middle range of impairment. There are differences between males and females with Fragile X with respect to their mental impairment.

Children with Fragile X often speak in rapid bursts or repeat words (echolalia). For males with Fragile X, the primary language difficulty is perseveration (inability to complete a sentence because of continuous repetition of words at the end of a phrase).

Although most children with Fragile X do not have serious physical problems , they are at greater risk for certain types of moderate medical problems than are normal children. Examples include, recurrent otitis media , eye problems such as myopia (nearsightedness) and a high incidence of strabismus . Orthopedic difficulties related to flat feet and joint laxity may occur. Twenty percent of males with Fragile X are prone to seizures , including petit mal, grand mal, and temporal lobe seizures. In addition, many children with Fragile X have digestive disorders , such as gastroesophageal reflux, that causes gagging, regurgitation, and discomfort.

Diagnosis and Treatment

A simple test is now available that can determine if a woman is carrier of the Fragile X gene. A drop of blood can be taken from the woman's finger and analyzed quickly and inexpensively. If a woman who is found to be a carrier is pregnant, she can arrange for testing of the fetus, which generally includes one or more of the following: chorionic villi sampling (CVS), amniocentesis and percutaneous umbilical blood sampling (PUBS). For a woman with a family history of retardation, testing before pregnancy will help determine if she is at risk.

In the best of circumstances, early identification of a child with Fragile X and subsequent treatment involves a team of professionals. These might include a speech and language pathologist, an occupational therapist (perhaps even a specialist in sensory integration), a physical therapist, a special education teacher, a genetics counselor, and a psychologist.

For further, more detailed information on this topic, please refer to the reference source for this page.

The information in this page is presented in summarised form and has been taken from the following source(s):
1. United States National Institutes of Health, National Institute of Child Health and Human Development:

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Contact Last modified: Jun 24 2002