What is fragile X syndrome?

Causes and Symptoms

Fragile X syndrome is caused by a change in a gene located on the long arm of the X chromosome. It is a sex-linked inherited
disease, transmitted from parent to child, with boys being affected much more often and more severely than girls. The prevalence of the disorder is estimated to be 1 in 4,000 males and 1 in 6 to 8,000 females worldwide.

While symptoms and their severity vary widely, common physical features of fragile X syndrome include a long, thin face, a prominent jaw and ears, a broad nose, a high palate, large testicles (macroorchidism) in males, and large hands with loose finger joints. Physical features are more subtle in females. Nonphysical features include a range of intellectual and learning disabilities, with the majority of affected males demonstrating a range from low-normal intelligence to severe intellectual disability. More recent research has found that the intelligence quotients (IQs) of males with fragile X syndrome appear to decline throughout childhood. Associated behavioral symptoms include unusual speech patterns, problems with attention span, hyperactivity, motor delays, and occasional autistic-type behaviors, such as poor eye contact, hand-biting, or hand-flapping.

Treatment and Therapy

While there is no cure for fragile X syndrome, a number of possible interventions can address various symptoms. Medications can be administered to assist with attention span and hyperactivity, as well as with aggressive behavior. Schools can provide children with assistance in speech, physical therapy, and vocational planning. Early childhood special education services for children prior to school age can provide necessary early intervention that may prove most helpful if indeed the rate of learning for children with fragile X syndrome slows with age. Genetic counseling is advised for families who carry the gene.

Perspective and Prospects

In 1969, the discovery was made of a break or fragile site on the long arm of the X chromosome. It was not until the 1980s, however, that consistent diagnoses of fragile X syndrome were made. In 1991, the responsible gene was sequenced and named the FMR-1 gene. Cytogenetic and deoxyribonucleic acid (DNA) testing are now available to identify affected persons.

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