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Turner syndrome is a chromosomal condition that affects development in females. Women with this condition tend to be shorter than average and are usually unable to conceive a child (infertile) because of an absence of ovarian function. Other features of Turner syndrome can include extra skin on the neck (webbed neck), puffiness or swelling (lymphedema) of the hands and feet, skeletal abnormalities, heart defects, and kidney problems. Developmental delays, learning disabilities, and behavioral problems are also possible, although these characteristics vary among affected females.
This condition occurs in about 1 in 2,500 female births worldwide, but is much more common among pregnancies that do not survive to term (miscarriages and stillbirths). Prenatal testing has probably decreased the number of diagnosed cases of this disorder.
Turner syndrome is related to the X chromosome.
The SHOX gene is associated with Turner syndrome.
People typically have two sex chromosomes in each cell; females have two X chromosomes, while males have one X chromosome and one Y chromosome. Turner syndrome results when a female's cells have one normal X chromosome and the other sex chromosome is missing or altered. The missing genetic material affects development and causes the characteristic features of the condition.
About half of individuals with Turner syndrome have monosomy X, which means each cell in the individual's body has only one copy of the X chromosome instead of the usual two sex chromosomes. Turner syndrome can also occur if one of the sex chromosomes is partially missing or rearranged rather than completely missing. Some women with Turner syndrome have a chromosomal change in only some of their cells, which is known as X-chromosome mosaicism.
Researchers have not yet determined which genes on the X chromosome are responsible for most signs and symptoms of Turner syndrome. They have, however, identified one gene called SHOX that is important for bone development and growth. Missing one copy of this gene likely causes short stature and skeletal abnormalities in women with Turner syndrome.
Most cases of this condition are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may lose a sex chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have a single X chromosome in each cell and will be missing the other sex chromosome.
X-chromosome mosaicism is also not inherited. It occurs as a random error during cell division in early fetal development. As a result, some of an affected person's cells have the usual two sex chromosomes (either two X chromosomes or one X chromosome and one Y chromosome), and other cells have only one copy of the X chromosome.
'''Turner syndrome''' is a human genetic abnormality, caused by a nondisjunction in the XY sex-determination system 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: *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 mole (skin marking)s, 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 (genetics) 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 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. Turner syndrome may be diagnosed by an amniocentesis during pregnancy. Sometimes, ... [ Read More ]
Turner's Syndrome Society, Texas - Providing links and information about Turner's Syndrome. Definition and Synonyms, FAQ, TSS Societies (National, State, and Local), Associated Links, Newsgroup discussions, Conference Information.
The Turner's Syndrome Society of the US - Learn about this disease, find medical information, order publications, share experiences, see some TS kids, and get screening information for TS.
The National University Hospital Turner Support Group - For patients with Turner Syndrome and their families, combined with the pharmaceutical company Serono Singapore Pte. Ltd. to co-organise biannual meetings and parties for the group.
National Library of Medicine - Offers synonyms for Turner syndrome, a summary and a list of major features.
Pediatric Oncall - Information about approach to a child with Turner's syndrome.
Turner Syndrome: Toward Early Recognition and Improved Outcomes - Detailed overview of this condition, including clinical features, genetics, diagnosis, defects and medical problems associated with the syndrome, and recommendations for treatment. Includes many photos. [Requires free registration.]
Turner Syndrome - A site prepared by the family of a young girl with TS. Includes her story, information about the syndrome and its treatment, FAQs, photos and links. [English, Turkish]
Turner Syndrome Clinical Trials - Explains the importance of participating in Turner Syndrome clinical trials and how even participants who take placebos contribute and benefit from volunteering.
NORD - Turner Syndrome - Offers alternative names, a general discussion and further resources.
Turners Syndrome Support - A personal site offering support and information.