XXX syndrome
XXX synodrome (Trisomy X)
Trisomy X, also known as triple X syndrome and characterized by the karyotypenote 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 women but it is rarely diagnosed; fewer than 10% of those with the condition know they have it.
Those who have symptoms can have learning disabilities, mild dysmorphic features such as hypertelorism (wide-spaced eyes) and clinodactyly (incurved little fingers), early menopause, and increased height. The average intelligence quotient (IQ) in trisomy X is 85–90. As the symptoms of trisomy X are often not serious enough to prompt a karyotype test, many cases of trisomy X are diagnosed before birth via prenatal screening tests such as amniocentesis. Research on girls and women with the disorder finds that cases which were diagnosed postnatally, having been referred for testing because of obvious symptoms, are generally more severe than those diagnosed prenatally. Most women with trisomy X live normal lives, although their socioeconomic status is reduced compared to the general population.
Trisomy X occurs via a process called nondisjunction, in which normal cell division is interrupted and produces gametes with too many or too few chromosomes. Nondisjunction is a random occurrence, and most girls and women with trisomy X have no family histories of chromosome aneuploidy. Advanced maternal age is mildly associated with trisomy X. Women with trisomy X can have children of their own, who in most cases do not have an increased risk of chromosome disorders; women with mosaic trisomy X, who have a mix of 46,XX (the typical female karyotype) and 47,XXX cells, may have an increased risk of chromosomally abnormal children.
First reported in 1959 by the geneticist Patricia Jacobs, the early understanding of trisomy X was that of a debilitating disability observed in institutionalized women. Beginning in the 1960s, studies of people with sex chromosome aneuploidies from birth to adulthood found that they are often only mildly affected, fitting in with the general population and that many never needed the attention of clinicians because of the condition.
- More information is available at [ Wikipedia:Trisomy X ]
XXY Syndrome
Klinefelter syndrome (KS), also known as 47,XXY, is a syndrome where a male has an additional copy of the X chromosome. The primary features are infertility and small, poorly functioning testicles. Often, symptoms are subtle and subjects do not realize they are affected. Sometimes, symptoms are more evident and may include weaker muscles, greater height, poor motor coordination, less body hair, breast growth, and less interest in sex. Often, these symptoms are noticed only at puberty. Intelligence is usually normal, but reading difficulties and problems with speech are more common.
Klinefelter syndrome occurs randomly. The extra X chromosome comes from the father and mother nearly equally. An older mother may have a slightly increased risk of a child with KS. The syndrome is defined by the presence of at least one extra X chromosome in addition to a Y chromosome yielding a total of 47 or more chromosomes rather than the usual 46. KS is diagnosed by the genetic test known as a karyotype.
While no cure is known, a number of treatments may help. Physical therapy, occupational therapy, speech and language therapy, counselling, and adjustments of teaching methods may be useful. Testosterone replacement may be used in those who have significantly lower levels. Enlarged breasts may be removed by surgery. About half of affected males have a chance of fathering children with the help of assisted reproductive technology, but this is expensive and not risk free. XXY males appear to have a higher risk of breast cancer than typical, but still lower than that of females. People with the condition have a nearly normal life expectancy.
Klinefelter syndrome is one of the most common chromosomal disorders, occurring in one to two per 1,000 live male births. It is named after American endocrinologist Harry Klinefelter, who identified the condition in the 1940s. In 1956, the extra X chromosome was identified as the cause. Mice can also have the XXY syndrome, making them a useful research model.
- More information is available at [ Wikipedia:Klinefelter syndrome ]
XYY Syndrome
XYY syndrome is a genetic condition in which a male has an extra Y chromosome. There are usually few symptoms. These may include being taller than average, acne, and an increased risk of learning disabilities. The person is generally otherwise normal, including typical rates of fertility.
The condition is generally not inherited from a person's parents but rather occurs as a result of a random event during sperm development. Diagnosis is by a chromosomal analysis, but most of those affected are not diagnosed within their lifetime. There are 47 chromosomes, instead of the usual 46, giving a 47,XYY karyotype.
Treatment may include speech therapy or extra help with schoolwork, but outcomes are generally good. The condition occurs in about 1 in 1,000 male births. Many people with the condition are unaware that they have it.
The condition was first described in 1961.
- More information is available at [ Wikipedia:XYY syndrome ]
Chat rooms • What links here • Copyright info • Contact information • Category:Root