In women, the premutation is liable to expand to more than repeats in cells that develop into eggs. This means that women with the FMR1 premutation have an increased risk of having a child with fragile X syndrome. By contrast, the premutation CGG repeat in men remains at the same size or shortens as it is passed to the next generation. Males and females who have a fragile X premutation have normal intellect and appearance. A few individuals with a premutation have subtle intellectual or behavioral symptoms, such as learning difficulties or social anxiety.
The difficulties are usually not socially debilitating, and these individuals may still marry and have children. Other neurologic findings include short-term memory loss, executive function deficits, cognitive decline, parkinsonism, peripheral neuropathy, lower-limb proximal muscle weakness, and autonomic dysfunction. The degree to which clinical symptoms of fragile X are present penetrance is age related; symptoms are seen in 17 percent of males aged years, in 38 percent of males aged years, in 47 percent of males aged years, and in 75 percent or males aged 80 years or older.
Some female premutation carriers may also develop tremor and ataxia. Females who have a premutation usually are unaffected, but may be at risk for premature ovarian failure and FXTAS. Premature ovarian failure POF is defined as cessation of menses before age 40 years, has been observed in carriers of premutation alleles.
A review by Sherman concluded that the risk for POF was 21 percent in premutation carriers compared to a 1 percent for the general population.
There are very few outward signs of fragile X syndrome in babies, but one is a tendency to have a large head circumference. An experienced geneticist may note subtle differences in facial characteristics.
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Fragile X syndrome. Actions for this page Listen Print. Summary Read the full fact sheet. On this page. Effects of Fragile X syndrome Fragile X syndrome can cause a range of physical, developmental, behavioural and emotional difficulties in people.
The most significant effects of Fragile X syndrome are: global developmental delay, including speech, language and communication difficulties intellectual disability and learning problems anxiety autism-like behaviours such as hand flapping, repeating words and sentences, and difficulty with social interactions attention deficit hyperactivity disorder ADHD poor eye contact difficulty processing sensory information.
Carriers of the Fragile X gene Although Fragile X syndrome is not that common, affecting around 1 in 3, boys and between 1 in 4, — 6, girls, the number of men and women who are carriers of the Fragile X gene is significantly higher. Testing and diagnosis of Fragile X syndrome Fragile X syndrome and Fragile X-associated disorders can only be diagnosed by DNA testing — usually by a blood test but sometimes via cheek swab or mouthwash.
DNA testing is recommended for: people with a family history of Fragile X syndrome or intellectual disability people with intellectual disability, developmental delay or learning disability together with features of Fragile X syndrome such as anxiety, ADHD or characteristics of autism spectrum disorder men or women over 50 with balance or gait problems, tremor or dementia any woman with problems with fertility or early menopause under 40 women with family history of primary ovarian insufficiency loss of function of the ovaries before age 40 for testing before or during pregnancy.
Genetic counselling services and Fragile X syndrome The facts about Fragile X syndrome are complicated and the ramifications for families can be serious.
Give feedback about this page. People who have FXS do not make this protein. People who have other fragile X-associated disorders have changes in their FMR1 gene but usually make some of the protein. FXS affects both males and females. However, females often have milder symptoms than males. The exact number of people who have FXS is unknown, but a review of research studies estimated that about 1 in 7, males about 1 in 11, females have been diagnosed with FXS.
Males who have FXS usually have some degree of intellectual disability that can range from mild to severe. Females with FXS can have normal intelligence or some degree of intellectual disability. A doctor or genetic counselor can order the test. Testing also can be done to find changes in the FMR1 gene that can lead to fragile X-associated disorders. This allows the family and other caregivers to learn more about the disorder and manage care so that the child can reach his or her full potential.
However, the results of DNA tests can affect other family members and raise many issues. So, anyone who is thinking about FXS testing should consider having genetic counseling prior to getting tested. FMR1 Disorders. Lancet Neurol. Neuroanatomical, molecular genetic, and behavioral correlates of fragile X syndrome. Brain Res Rev. Epub Jul Fragile X syndrome and associated disorders: Clinical aspects and pathology. Neurobiol Dis.
Epub Jan Fragile X syndrome: diagnostic and carrier testing. Genet Med. FMR1 and the continuum of primary ovarian insufficiency. Semin Reprod Med. Epub Oct 3. The Fragile X premutation: new insights and clinical consequences. Eur J Med Genet.
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