Turner syndrome

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. Common symptoms of Turner syndrome include:

Related Topics:
Genetic abnormality - Nondisjunction - Sex chromosomes - X chromosome

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• 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.

Related Topics:
Cubitus valgus - Webbed neck - Mole

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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.

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There are no known risk factors for Turner syndrome.

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Approximately 98% of all foetuses with Turner syndrome spontaneously abort. Foetuses with Turner syndrome make up about 10% of the total number of spontaneously aborted foetuses in the United States. The incidence of Turner syndrome in live births is between 1 in 2,500 and 1 in 3,000.

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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.

Related Topics:
Amniocentesis - Ultrasound - Genetic counseling

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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.

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Turner syndrome: Diagnosis ►