Fragile X Syndrome

What is Fragile X Syndrome?
Fragile X Syndrome (FXS) is a hereditary disease and the most common inherited cause of mental impairment. Fragile X Syndrome causes mild to severe mental impairment and includes physical and behavioral characteristics.

Causes of Fragile X Syndrome
Fragile X Syndrome occurs when a certain gene (FMR-1) mutates or changes. The FMR-1 gene mutates by expanding or repeating certain chemical components of DNA (CGG). Everyone has the FMR-1 gene, but whereas the general population has between 5 and 40 repeats, carriers of FXS have between 55 and 200 repeats. This is called the premutation stage. Individuals with the full mutation have over 200 repeats. The full mutation causes the FMR-1 gene to turn off. That means the FMR-1 gene is not working properly and not producing the protein it is supposed to. This protein is crucial to intellectual development and functioning.

Characteristics of Fragile X Syndrome
Characteristics of Fragile X Syndrome fall into three categories: physical, behavioral and cognitive. Males are usually more affected by these characteristics than females.

Adult males often have physical characteristics such as large or prominent ears, a long face and enlarged testicles. Males often also have loose connective tissue, often resulting in double-jointed fingers, a heart murmur (mitral valve prolapse) and/or flat feet. Females and younger children with Fragile X Syndrome may have these same features or may look similar to the general population.

The behavioral characteristics of FXS individuals are exhibited throughout a wide range — anywhere from friendly to autistic-like. Sensory stimulation, such as noise, a light touch or crowds of people, is also overwhelming in individuals with FXS.

The cognitive characteristics of Fragile X Syndrome range from learning disabilities and a normal IQ to severe disabilities and autism. The most common cognitive difficulties include attention deficits, hyperactivity and delayed developmental milestones such as walking and talking.

Diagnosis
Fragile X Syndrome is diagnosed with a simple blood test, called the FMR-1 gene test. This is the only accurate way a diagnosis can be made.

Family History Risk Factors
If you have a child or relative with a disability or developmental delay, or have a father with balance or tremor problems, ask your doctor about FXS.

Genetic Counseling
Genetic counseling is a wonderful resource for individuals diagnosed with FXS or their family members. Genetic counselors who are familiar with FXS can offer information on testing, family planning options and inheritance patterns as well as support and coping strategies.

Treatment
Treatment for Fragile X Syndrome individuals is available. Specialists help individuals with coping strategies that allow them to reach their full potential.

It’s a good idea to screen for Fragile X Syndrome during your pregnancy so that the expecting couple can start informing themselves about the disease and how to offer coping strategies to their new child.

For more information, visit the National Fragile X Foundation.

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