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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 differently 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.
While most of the side effects of Turner syndrome are harmless, some can lead to significant medical problems.
Between 5% and 10% of those born with Turner syndrome have coarctation of the aorta, a condition which if untreated causes blood to flow in a thin, fast stream against the side of the heart. This can lead to heart rupture. Coarctation of the aorta can be corrected surgically as soon as it is detected.
Up to 15% of adults with Turner syndrome have bicuspid aortic valves, meaning that there are only two, instead of three, parts to the valves in the main blood vessel leading from the heart. Because bicuspid valves are capable of regulating blood flow properly, this condition may go undetected without regular screening. Because bicuspid valves must work harder than ordinary heart valves, they are more likely to deteriorate and later fail.
Turner syndrome is often associated with persistent hypertension, sometimes even in childhood. In the majority of Turner syndrome patients with hypertension, there is no specific cause. In the remainder, it is usually associated with heart or kidney abnormalities.
Normal skeletal development is inhibited due to a large variety of factors, mostly hormonal. The head, neck, and chest of women with Turner syndrome are usually of normal size, but the arms and legs are unusually short. The average height of a woman with Turner syndrome is 4'7", or about 140cm.
The fourth metacarpal bone (fourth toe and ring finger) may be unusually short.
Due to inadequate circulation of estrogen, many of those with Turner syndrome develop osteoporosis. This can decrease height further, as well as exacerbate the curvature of the spine, possibly leading to scoliosis. It is also associated with an increased risk of bone fractures.