LYCOS RETRIEVER 
Fragile X Syndrome: Females
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Fragile X syndrome is a genetic disorder caused by a mutation (a change in the genetic information) of a specific gene. The parents or other family members did not do anything to cause it. The gene mutation has usually been carried unknowingly for many generations. Both males and female carriers can have a small fragile X mutation (called a premutation) and have a normal IQ. The premutation can expand to a larger full mutation when it is passed on to the next generation through a female. It is the full mutation that causes fragile X syndrome. Your child may be the first one in your family with behavior or development problems, or there may be other relatives who are affected by the fragile X mutation.
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This final report reviews the second phase of a life-span study of boys with fragile X syndrome (FSX), the most common known inherited cause of mental retardation. Males with the syndrome are more severely affected than females and in males, delays are usually evident in all the developmental domains, although cognitive and communication skills are likely to be most affected. The project studied 61 elementary school aged boys and their families. Approximately 25% of the boys were found to ... meet diagnostic criteria for autism. It was noted that when autistic behavior and FXS co-occur, the effect on development appears to be additive. The heart rates of the boys with FXS were significantly higher than of typically developing children, and their visual-motor skills were less than half than would be typically expected.
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Fragile-X syndrome is an X-linked, semi-dominant disorder with reduced penetrance. In addition to being associated with characteristic physical and behavioural features, it causes intellectual disabilities ranging from mild to severe. It is the most common cause of inherited intellectual disability and is second only to Down's syndrome as the most common genetic cause of intellectual disability. There are about 100-200 affected births in the UK each year. The population prevalence is estimated at 1 in 4000 males and 1 in 8000 females. It occurs in all races and ethnic groups.
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Fragile X syndrome (FXS) is the most common known cause of inherited mental impairment. According to the Centers for Disease Control (CDC), between 1 in 4000 and 1 in 6000 males is affected with FXS. Although the prevalence of the disorder in females is less certain, the CDC estimates that at least 1 in 8000 females has FXS.
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Individuals with a premutation do not express the clinical symptoms associated with fragile X syndrome, although it has been reported that pre-mutation carrier females can experience premature ovarian failure. Individuals who carry the full mutation can express symptoms of fragile X syndrome because they are missing the protein produced by the FMR1 gene. Males with a full mutation always exhibit some symptoms of the disorder. Due to X inactivation, females with a full mutation may or may not express symptoms.
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Developmental delays are the most significant characteristic of those with fragile X. The range of learning problems is wide. Some are affected in fairly small ways, while at the other end of the scale, especially with males, there can be severe intellectual disabilities. Most affected males fall somewhere in the middle. Learning disabilities are often accompanied by delays in speech and communication skills. There can ... be delays in both gross motor (such as sitting and walking) and fine motor (such as holding a pencil) skills. In general, females are not as delayed as males.
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