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Turner syndrome (TS) also known as Ullrich–Turner syndrome, gonadal dysgenesis, and 45,X, is a condition in which a female is partly or completely missing an X chromosome. Signs and symptoms vary among those affected. Often, a short and webbed neck, low-set ears, low hairline at the back of the neck, short stature, and swollen hands and feet are seen at birth. Typically they are without menstrual periods, do not develop breasts, and are unable to have children. Heart defects, diabetes, and low thyroid hormone occur more frequently. Most people with TS have normal intelligence. Many, however, have troubles with spatial visualization such as that needed for mathematics. Vision and hearing problems occur more often.〔 Turner syndrome is not usually inherited from a person's parents.〔 No environmental risks are known and the mother's age does not play a role.〔 Turner syndrome is due to a chromosomal abnormality in which all or part of one of the X chromosomes is missing or altered. While most people have 46 chromosomes, people with TS usually have 45. The chromosomal abnormality may be present in just some cells in which case it is known as TS with mosaicism.〔 In these cases, the symptoms are usually fewer and possibly none occur at all. Diagnosis is based on physical signs and genetic testing. No cure for Turner syndrome is known. Treatment, however, may help with symptoms. Human growth hormone injections during childhood may increase adult height. Estrogen replacement therapy can promote development of the breasts and hips. Medical care is often required to manage other health problems with which TS is associated. Turner syndrome occurs in between one in 2000 and one in 5000 females at birth. All regions of the world and cultures are affected about equally. People with TS have a shorter life expectancy, mostly due to heart problems and diabetes. Henry Turner first described the condition in 1938. In 1964, it was determined to be due to a chromosomal abnormality. == Signs and symptoms == Of the following common symptoms of Turner syndrome, an individual may have any combination of symptoms and is unlikely to have all symptoms. * Short stature * Lymphedema (swelling) of the hands and feet * Broad chest (shield chest) and widely spaced nipples * Low hairline * Low-set ears * Reproductive sterility * Rudimentary ovaries gonadal streak (underdeveloped gonadal structures that later become fibrotic) * Amenorrhoea, the absence of a menstrual period * Increased weight, obesity * Shortened metacarpal IV * Small fingernails * Characteristic facial features * Webbed neck from cystic hygroma in infancy * Aortic valve stenosis * Coarctation of the aorta * Bicuspid aortic valve * Horseshoe kidney * Visual impairments - sclera, cornea, glaucoma, etc. * Ear infections and hearing loss * High waist-to-hip ratio (the hips are not much bigger than the waist) * Attention deficit hyperactivity disorder (problems with concentration, memory, attention with hyperactivity seen mostly in childhood and adolescence) * Nonverbal learning disability (problems with math, social skills, and spatial relations) Other features may include a small lower jaw (micrognathia), cubitus valgus,〔Chapter on Amenorrhea in: 〕 soft upturned nails, palmar crease, and drooping eyelids. Less common are pigmented moles, hearing loss, and a high-arch palate (narrow maxilla). Turner syndrome manifests itself differently in each female affected by the condition; therefore, no two individuals share the same features. While most of the physical findings are harmless, significant medical problems can be associated with the syndrome. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Turner syndrome」の詳細全文を読む スポンサード リンク
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