Clinical Features of Turner Syndrome
Turner syndrome affects approximately 1 out of every 2,500 female live births worldwide. It embraces a broad spectrum of features, from major heart defects to minor cosmetic issues. Some individuals with Turner syndrome may have only a few features, while others may have many. Almost all people with Turner syndrome have short stature and loss of ovarian function, but the severity of these problems varies considerably amongst individuals.
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Some individuals with Turner syndrome have a short neck with a webbed appearance, a low hairline at the back of the neck, and low-set ears. Hands and feet of affected individuals may be swollen or puffy at birth, and often have soft nails that turn upward at the ends when they are older. All these features appear to be due to obstruction of the lymphatic system during fetal development. Another characteristic cosmetic feature is the presence of multiple pigmented nevi, which are colored spots on the skin, or moles.
Almost all individuals with Turner syndrome have short stature. This is partially due to the loss of one copy of the SHOX gene on the X-chromosome. This particular gene is important for long bone growth. The loss of SHOX may also explain some of the skeletal features found in Turner syndrome, such as short fingers and toes, and irregular rotations of the wrist and elbow joints. Linear growth is attenuated in utero, and statural growth lags during childhood and adolescence, resulting in adult heights of 143-145 cm (approximately 4 feet 8 inches). Final adult height in Turner syndrome can be increased by a several inches if growth hormone (GH) treatment is given relatively early in childhood.
Unknown genes on the X-chromosome regulate the development and functions of the ovary. Most individuals with Turner syndrome experience loss of ovarian function early in childhood, and thus do not enter puberty at the normal age.
Some teenagers may undergo some breast development and begin menstruating, but cease further development and menses during the later teen years. A few women with Turner syndrome have apparently normal ovarian function with regular menses until the mid-20s before ovarian failure occurs. A few spontaneous pregnancies have been reported.
It is standard medical practice to treat girls with Turner syndrome with estrogen to induce breast development and other features of puberty if Spontaneous puberty does not occur. Girls and women with Turner syndrome should takeestrogen-progesterone treatment to maintain their secondary sexual development and to protect their bones from osteoporosis until ~ the usual age of menopause (50 years).
Most women with Turner syndrome do not have ovaries with healthy oocytes capable of fertilization and embryo formation. Current assisted reproductive technology, however, may allow women to become pregnant with donated oocytes. However, the risk of maternal complications such as diabetes, high blood pressure and aortic dissection, is high in women with Turner syndrome.
From 5-10% of children with Turner syndrome are found to have a severe constriction of the major blood vessel coming out from the heart, a condition known as "coarctation of the aorta." This can be surgically corrected as soon as it is diagnosed.
Other major defects in the heart and its major vessels are reported to a much lesser degree. Approoximately 30% of individuals with Turner syndrome are reported to have "bicuspid aortic valves," meaning that the major blood vessel from the heart has only two rather than three components to the valve regulating blood flow. This condition has been discovered mainly by medical imaging studies on women without symptoms, and may not be clinically obvious. It requires careful medical monitoring, since bicuspid aortic valves can deteriorate or become infected. Comprehensive screening and evaluation by a cardiologist with expertise in congenital heart conditions is essential for all patients with Turner syndrome at the time of diagnosis. The evaulation should include cardiac magnetic resonance as well as echocardiography and ECG.
Many women with Turner syndrome have high blood pressure, which may be apparent even in childhood. In some cases this high blood pressure may be due to aortic constriction, or to kidney abnormalities (see Kidney section below). In a majority of women, however, no specific cause for the high blood pressure has been found.
Kidney malformations affect ~ 1/3 of individuals with Turner. T. While the kidneys usually function normally, there may be a tendency towards urinary infections.
There is a high incidence of osteoporosis—meaning thin or weak bones—in women with Turner syndrome. Osteoporosis leads to loss of height, curvature of the spine and increased bone fractures.
The primary cause of osteoporosis in individuals with Turners appears to be inadequate circulating estrogen in the body. Turner women who have low levels of estrogen due to ovarian failure can take estrogen treatments, which will help prevent osteoporosis. It is possible that other factors contribute to the severity of osteoporosis in Turner syndrome. For example, there may be defects in bone structure or strength related to the loss of unknown X-chromosome genes. This is an area of major medical significance, which demands further study to help prevent osteoporosis and fractures in women with Turner syndrome.
Type II diabetes, also known as adult onset diabetes, has a high occurrence rate in individuals with Turner syndrome.
Individuals with Turner syndrome have twice the risk of the general population for developing this disease. The reason for the high risk of diabetes amongst individuals with Turner syndrome is unknown but there appears to be insufficient insulin release in response to glucose.
Diabetes type II can be controlled through careful monitoring of blood-sugar levels, diet, exercise, regular doctor visits and sometimes medication.
Approximately 1/3 of individuals with Turner syndrome have a thyroid disorder, usually hypothyroidism. Symptoms of this condition include decreased energy, dry skin, cold-intolerance and poor growth.
In most cases, it is caused by an immune system attack on the thyroid gland (also known as Hashimoto's thyroiditis). Although it is not known why thyroid disorders occur with a high frequency in Turner syndrome, the condition is easily treated with thyroid hormone supplements.
In general, individuals with Turner syndrome have normal intelligence. However, some girls and women with Turner syndrome may have difficulty with specific visual-spatial coordination tasks (e.g. mentally rotating objects in space) and learning math (geometry, arithmetic). This very specific learning problem has been termed the "Turner neurocognitive phenotype" and appears due to loss of X-chromosome genes important for selected aspects of nervous system development. The verbal skills of individuals with Turner syndrome are usually normal or superior.