Turner syndrome is a human genetic abnormality, caused by a nondisjunction in the sex chromosomes that occurs in females (1 out of every 2,500 births). Instead of the normal XX sex chromosomes, only one X chromosome is present and fully functional; this is called 45,X or X0. In Turner syndrome, female sexual characteristics are present but underdeveloped. more...
Common symptoms of Turner syndrome include:
- Short stature
- Lymphoedema (swelling) of the hands and feet
- Broad chest and widely-spaced nipples
- Low hairline
- Low-set ears
- Reproductive sterility
Other symptoms include a small lower jaw, cubitus valgus (turned-out elbows), a webbed neck, and soft, upturned nails. Less common are pigmented moles, hearing loss, and a high-arch palate. Turner syndrome manifests itself differently in different people, and no two women need share the same symptoms.
Turner syndrome is caused by the loss of genetic material from one of the sex chromosomes. In Turner syndrome, the embryo has only one functioning sex chromosome. This chromosome is always an X chromosome, as an embryo with only a Y chromosome is incapable of survival. The remaining X chromosome is either absent or damaged. Mosaic Turner syndrome, where some of the cells have two sex chromosomes but others have only a single functioning X chromosome, is also possible. In cases of mosaic Turner syndrome, the symptoms are usually less pronounced.
There are no known risk factors for Turner syndrome.
Approximately 98% of all fetuses with Turner syndrome spontaneously abort. Fetuses with Turner syndrome make up about 10% of the total number of spontaneously aborted fetuses in the United States. The incidence of Turner syndrome in live births is between 1 in 2,500 and 1 in 3,000.
The syndrome is named after Henry Turner, an Oklahoma endocrinologist, who described it in the 1940s. In Europe, it is often called Ullrich-Turner syndrome or even Bonnevie-Ulrich-Turner syndrome to acknowledge that earlier cases had also been described by European doctors.
Turner syndrome may be diagnosed by an amniocentesis during pregnancy. Sometimes, fetuses with Turner syndrome are identified by abnormal ultrasound findings (i.e. heart defect, kidney abnormality, cystic hygroma, ascities). Although the recurrence risk is not increased, genetic counseling is often recommended for families who have had a pregnancy or child with Turner syndrome.
A blood test, called a karyotype, analyzes the chromosomal composition of the individual. This is the most commonly used blood test to diagnose Turner syndrome.
Medical consequences of Turner syndrome
While most of the symptoms of Turner syndrome are harmless, some can lead to significant medical problems.
It is interesting for a better understanding to first consider the results of Price et al, 1986 study of 156 female patients with Turner syndrome. Indeed they showed a significantly greater number of deaths from diseases of the circulatory system than expected, half of them due to congenital heart disease. The interesting finding is that when patients with congenital heart disease were omitted from the sample of the study, the mortality from circulatory disorders was not significantly increased.
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