LYCOS RETRIEVER 
Fragile X Syndrome: Females
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Fragile X syndrome is the single most common inherited cause of mental impairment. Current estimates of its prevalence vary, but some experts believe that fragile X affects at least 1 in 1000 males and females of all races and ethnic groups. More conservative estimates put the frequency at 1 in 1500 males and 1 in 2500 females (Warren, Jama, Feb. 16, 1994 - Vol.271, No.7, p.536). The discrepancy in these numbers is due to the fact that large-scale population studies of the incidence of fragile X have not yet been done. In either case, fragile X is one of the most common genetic diseases in humans. It is estimated that 80-90% of people with fragile X are not yet correctly diagnosed.
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Attentional deficits are more common in fragile-X syndrome than in other causes of intellectual disability. Inattentiveness, restlessness and fidgetiness tend to persist over time. Premutation carriers have increased social anxiety and mood lability. It may be difficult to distinguish delusions and hallucinations from the usual fragile-X behaviour, which may include perseverative mumbling and stereotypies. In female carriers, schizotypal features are more common in mildly affected people and fragile-X positive heterozygotes, and depression in fragile-X negative heterozygotes. The occurrence of comorbid bipolar affective disorder in other family members has been described.
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According to the National Fragile X Foundation, it is estimated that 37,200 males in the United States are affected with FXS, of which approximately 9,700 are under the age of 18. The Foundation estimates that about 62,500 U.S. females are predicted to carry a Fragile X allele (genetic mutation).(1) Both males and females can be carriers for either the pre- mutation or full mutation of the FXS gene. Twenty percent of female carriers of the Fragile X pre-mutation will experience fertility problems due to premature ovarian failure,(4) while 39 percent of male pre-mutation carriers will develop symptoms of tremor and clumsiness after the age of 50.(5)
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The most noticeable and consistent effect of Fragile X is on intelligence. More than 80 percent of males with Fragile X have an IQ (intelligence quotient) of 75 or less.1 The effect of Fragile X on intelligence is more variable in females. Some females have mental impairment, some have learning disabilities, and some have a normal IQ.
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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.
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There are very few outward signs of Fragile X syndrome in babies. Babies may have a large head circumference. Measurement of oversized testes in males who have reached puberty may ... suggest the diagnosis. An experienced geneticist may note subtle differences in facial characteristics. Mental retardation is the hallmark of this condition and, in females, this may be the only sign of the problem.
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