XO syndrome

Related Terms

Bonnevie-Ullrich syndrome, gonadal dysgenesis, monosomy X, Morgagni-Turner-Albright syndrome, ovarian dwarfism, ovary aplasia, pterygolymphangiectasia, Schereshevkii-Turner syndrome, sex chromosomes, Turner type, Turner-Varny syndrome, Ullrich-Turner syndrome, X chromosome, X syndrome, XO syndrome.

Background

Everyone has two sex chromosomes. Healthy males have one X and one Y chromosome, while healthy females have two X chromosomes. Turner syndrome occurs when a female is missing part of, or an entire, X chromosome at birth.
Normally, girls have two X chromosomes that contain the genetic information needed to develop sexual characteristics. Other genes important to development are also present in the X chromosomes. Therefore, females with Turner syndrome have developmental abnormalities, such as a short stature and reproductive problems.
Turner syndrome is not usually considered life threatening. However, many patients develop heart, kidney, and thyroid problems, as well as other abnormalities that require lifelong monitoring and treatment.
Although there is currently no cure for Turner syndrome, treatment is available to manage the symptoms and related conditions. Most women with Turner syndrome are able to live long, healthy lives. Many women are able to have children with the help of hormone therapy and/or fertility treatments.
Researchers estimate that Turner syndrome affects about one female out of 2,000-5,000 live births.

Signs and symptoms

General: Symptoms of Turner syndrome vary in severity based on how much of the X chromosome is missing. The following section describes the most common abnormalities associated with Turner syndrome.
Early signs: Turner syndrome may be suspected at birth if a newborn has loose skin at the back of the neck, swollen hands and feet, an underdeveloped midface that looks concave, widely spread nipples, a heart murmur, and a faint pulse.
Short stature: At birth, girls with Turner syndrome may be slightly shorter (about 18.5 inches) than average (about 20 inches). These girls remain shorter than their peer group for the rest of their lives. If left untreated, most girls with Turner Syndrome do not experience a normal growth spurt. Instead, they continue to grow slowly until they reach their 20s. With treatment, most women grow to be about four feet, eight inches as adults.
Reproductive problems: Many females with Turner Syndrome are born with only remnants of ovaries, rather than fully developed ovaries. In such cases, the ovaries are unable to produce eggs or hormones that are needed for sexual development and growth. In some girls, the ovaries may appear to be normal during childhood, but then stop functioning early in life. When the ovaries are not functional, the condition is often called ovarian hypofunction.
In healthy females, the ovaries produce hormones that trigger the development of sexual characteristics. Therefore, girls with Turner syndrome often do not develop secondary sexual characteristics, such as breasts, body hair (including pubic hair), or wider hips. Without functional ovaries, girls have irregular menstrual cycles or do not menstruate at all. When menstruation does not occur, it is called amenorrhea. However, estrogen supplementation helps stimulate menstruation. Many women are able to have children with the help of estrogen therapy or with the use of donor eggs. It is important to note that women with Turner syndrome have a higher risk of complications during pregnancy.
Learning disabilities and social difficulties: Most females with Turner syndrome have normal intelligence quotients (IQs). However, some may have difficulty with nonverbal concepts, such as math and spatial reasoning. They may also have difficulty understanding nonverbal cues or gestures during social interactions.
Other physical characteristics: Several other characteristic physical features associated with Turner syndrome include low-set ears, a receding lower jaw or arched upper jaw, drooping or lazy eyes, low hairline at the back of the head, loose skin at the back of the neck (called loose nuchal skin), broad chest, flat feet, fingernails that turn upward, swelling of the hands and feet (especially at birth), and arms that turn outward at the elbows (called cubitus valgus). Women may experience all or some of these characteristics, which may be present at birth or develop later in life.

Diagnosis

Karyotyping: Most cases of Turner syndrome are diagnosed during infancy, although it can be diagnosed at any age. If Turner syndrome is suspected, a giemsa banded karyotype test is performed on the patient's white blood cells. This test provides a picture of the person's chromosomes. A sample of the patient's blood is taken and analyzed for the absence of all or part of the X chromosome. If the patient does not have two complete X chromosomes, a positive diagnosis is made.
Prenatal screening and diagnosis: In some cases, Turner syndrome may be suspected during pregnancy. For instance, if a doctor detects heart or kidney abnormalities, thickening of the skin at the back of the neck, cystic hygromas (a cyst that looks like a soft bulge under the skin), and shortened thigh bones during an ultrasound at the mid-trimester of pregnancy, Turner syndrome may be suspected.
If Turner syndrome is suspected based on the results of prenatal screening, a mother may choose to undergo diagnostic tests during pregnancy. Amniocentesis and chorionic villus sampling (CVS) can diagnose Turner syndrome with 98-99% accuracy. However, there are serious risks associated with these tests. Patients should discuss the potential health benefits and risks associated with these procedures before making any medical decisions.
During amniocentesis, a long needle is carefully inserted through the abdominal wall and into the uterus. A small amount of amniotic fluid is then collected from the sac surrounding the fetus for a genetic analysis. This test is performed after 15 weeks of gestation. Some experts estimate that the risk of miscarriage ranges from one out of 200-400 patients; it is highest when the procedure is done early in pregnancy, before the two layers of fetal membranes have sealed. A woman's particular risk depends in large part on the skill and experience of the doctor performing the procedure. Some patients may experience minor complications, such as cramping, leaking fluid, or irritation where the needle was inserted.
During chorionic villus sampling (CVS), a small piece of tissue (chorionic villi) is removed from the placenta during early pregnancy. Depending on where the placenta is located, CVS can be performed through the cervix or through the abdomen. The tissue sample is then analyzed for the absence of all or part of one X chromosome. This procedure may be performed between the ninth and 14th week of gestation. The risks of infection or fetal damage are slightly higher than the risks of amniocentesis. Miscarriage occurs in about two percent of women who undergo this procedure. There appears to be an even higher risk of miscarriage with the transcervical CVS technique compared to the transabominal technique. Other factors that further increase the risk of CVS include having the procedure performed three or more times and having a fetus that is smaller than normal. The physician's skill and experience also play an important role.
Other: Once Turner syndrome is diagnosed, additional tests may be performed to evaluate and/or monitor the patient's condition. For example, people may need to visit a cardiologist to determine if they have valvular abnormalities or aortic coarctation. An ultrasonography of the heart, kidney, and ovaries may be performed to detect abnormalities in the functionality of these organs. Blood tests may be performed to determine if the patient has developed an endocrine disorder (e.g. diabetes, hypothyroidism, or hyperthyroidism), high cholesterol, or autoantibodies (e.g. thyroid peroxidase antibodies). Psychometric testing may be performed in older children to determine if they have learning disabilities.

Complications

Anorexia nervosa: Some patients may develop anorexia nervosa when they begin treatment with estrogen therapy. However, the relationship between the eating disorder and estrogen therapy is not clearly understood or established.
Autoimmune disorders: People with Turner syndrome have an increased risk of developing autoimmune disorders that affect the thyroid gland. A condition called autoimmune thyroiditis, or Hashimoto's disease, is common among Turner syndrome patients. The disorder occurs when the immune system attacks the patient's thyroid gland, causing the thyroid to swell. The thyroid gland, located in the neck, produces hormones called triodothyronin (T3) and thyroxine (T4). These hormones control growth and the rate at which the body uses energy (metabolism). The inflammation caused by Hashimoto's disease often leads to an underactive thyroid gland, called hypothyroidism. Therefore, patients with the condition may experience slowed development and fatigue. Patients typically receive lifelong treatment with hormones to make up for their underactive thyroids. Some patients may need to have their thyroid gland surgically removed. With lifelong hormone supplementation, these patients are also able to live normal, healthy lives.
Patients with Turner syndrome also have an increased risk of developing Grave's disease, a condition that causes the thyroid gland to become overactive. In Graves' disease, the body's immune system releases abnormal antibodies that mimic thyroid stimulating hormone (TSH). As a result, the thyroid produces too many hormones. Several medications and surgical procedures are available for patients with Grave's disease. The best approach depends on age, physical health, and the severity of the condition.
Chronic liver disease: Turner syndrome has also been associated with an increased risk of chronic liver disease.
Colon cancer: Some studies indicate that people with Turner syndrome may have an increased risk of developing colon cancer.
Diabetes: Patients with Turner syndrome have an increased risk of developing diabetes relative to the general population.
Ear infections: Patients with Turner syndrome have an increased risk of acquiring ear infections.
Hearing loss: Patients with Turner syndrome have an increased risk of experiencing sensorineural hearing loss later in life. This type of hearing loss occurs when there is damage to the inner ear or the nerves that send signals from the ear to the brain. Sensorineural hearing loss is permanent and cannot be corrected.
Heart defects: About a third of people with Turner syndrome have heart defects. The most common type of heart abnormality occurs when the aorta or bicuspid valve is narrower than normal. Both of these structures promote blood flow through the heart. Patients may also have an increased risk of high blood pressure.
High cholesterol: Patients with Turner syndrome have an increased risk of developing high cholesterol. Too much cholesterol in the blood is a major risk factor for heart disease, which may lead to a heart attack, heart failure, stroke, and death.
Inflammatory bowel disease (IBD): Patients with Turner syndrome have an increased risk of developing inflammatory bowel disease (IBD). This term refers to two chronic diseases that cause inflammation of the intestines: ulcerative colitis and Crohn's disease. Although Crohn's disease can cause inflammation in any area of the gastrointestinal tract from the mouth to the anus, it most commonly affects the ileum (small intestine) and/or colon. Ulcerative colitis is different from Crohn's disease because inflammation is limited to only the colon. Also, ulcerative colitis only affects the superficial layers (the mucosa) of the colon.
Kidney problems: About 33% of people with Turner syndrome are born with kidney abnormalities. Although these defects do not usually cause medical problems, they may result in an increased risk of urinary tract infections (UTIs). Patients with Turner syndrome also have an increased risk of experiencing pyelonephritis or inflammation of the kidney that is usually caused by a bacterial infection.
Obesity: Turner syndrome patients are also more likely to be overweight or obese than the general population.
Obstructive uropathy: People with Turner syndrome have an increased risk of developing obstructive uropathy. This condition occurs when there is a blockage in the urinary tract that stops or limits the flow of urine. If left untreated, obstructive uropathy may cause urine to back up into the kidneys, which may lead to kidney damage.
Problems during pregnancy: Many women with Turner syndrome are able to have children with the help of estrogen therapy or with the use of a donor egg (in vitro fertilization techniques). However, patients with the disorder have an increased risk of experiencing complications during pregnancies, including miscarriage. Additionally, their children have an increased risk of having chromosomal abnormalities.
Scoliosis: People with Turner syndrome are also more likely to develop scoliosis, a condition in which the spine curves abnormally. Screening for scoliosis is simple and often orthopedic braces or surgery can correct this curvature. Patients with scoliosis may also benefit from back braces.

Treatment

General: Although Turner syndrome is not usually life threatening, patients generally require lifelong treatments to manage the symptoms and related illnesses. Most women with Turner syndrome are able to live long, healthy lives.
Patients with Turner syndrome should stay in close contact with a variety of medical specialists and are encouraged to undergo routine medical checkups and recommended screenings. Patients often need to undergo annual blood tests to check for signs of heart, kidney, or thyroid problems.
Behavioral therapy: Researchers are currently studying behavioral therapy as a possible treatment for specific learning difficulties in patients with Turner syndrome. Several different types of behavioral therapy are available to help patients improve their communication and social skills, as well as their learning abilities and adaptive behaviors. Evidence suggests that behavioral therapy is most effective if it is started early in life, when the patient is 3-4 years old or younger.
Recombinant human growth hormone (hGH): Many patients with Turner syndrome receive recombinant human growth hormone (hGH) therapy with somatropin to improve their height and assure full sexual development. Patients typically receive hGH injections several times a week. Some evidence suggests that hGH therapy increases the height of girls with Turner syndrome by an average of three inches during the first year of treatment.
Estrogen: Once girls with Turner syndrome reach puberty (about 12 years of age), they often require estrogen therapy. This therapy is generally continued for several years until the patient has reached full sexual maturity or until the normal age of menopause. Estrogen therapy has been shown to help patients grow, develop normal female sexual characteristics, begin menstruating, develop proper bone structure, and prevent osteoporosis.
Fertility treatments: In addition to hormonal therapies, some women may choose to undergo fertility treatments in order to have children. In vitro fertilization is one of the most common procedures used in Turner syndrome patients. During the procedure, mature eggs are taken from a woman and combined with a man's sperm in a laboratory. Once the eggs and sperm have combined to form embryos, they are implanted into the female's uterus. Because several embryos are implanted into the female's uterus, there is an increased chance of having more than one baby. This treatment also requires daily hormone injections and frequent blood tests. There are ethical issues regarding in vitro fertilization, particularly in relation to the moral status of gametes (unfertilized egg and sperm), of pre-implantation fertilized eggs, embryos, and of the unborn fetus.

Integrative therapies

Currently, there is a lack of scientific data on the use of integrative therapies for the treatment or prevention of Turner syndrome.

Prevention

There is currently no known method of prevention for Turner syndrome. This disorder occurs randomly and is not inherited. Therefore, if a mother has the disorder, it does not necessarily mean that her daughters will as well.
If Turner syndrome is suspected during pregnancy, prenatal screening and diagnostic tests may be performed to determine if a mother's fetus has the disorder.
Patients with Turner syndrome should stay in close contact with a variety of medical specialists and are encouraged to undergo routine medical checkups and recommended screenings. Patients often need to undergo annual blood tests to check for signs of heart, kidney, and thyroid problems and other possible complications.

Author information

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

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Guttmann H, Weiner Z, Nikolski E, et al. Choosing an oestrogen replacement therapy in young adult women with Turner syndrome. Clin Endocrinol (Oxf). 2001 Feb;54(2):159-64.
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Causes

Genetic mutation: Healthy females have two X chromosomes. These chromosomes are called sex chromosomes because they contain the genetic information that is needed to develop sexual characteristics. Turner syndrome occurs when a female is missing one or part of one X chromosome at birth.
Other genes important to development are also present in the X chromosomes. For instance, the short stature homeobox (SHOX) is found in both X chromosomes; it helps control a person's bone development and height. Because females with Turner syndrome are missing part or all of one X chromosome, they are missing their second copy of the SHOX gene. As a result, they are shorter than average.
Variations of Turner syndrome: The most common genetic variation of Turner syndrome occurs when a female is missing one complete X chromosome in all of her cells. This is called the 45, X Karyotype, or X chromosome monosomy. Evidence suggests that the intact chromosome may be just as likely to come from the mother as the father. In other words, there does not appear to be a parental pattern of responsibility for the deleted chromosome.
A less common variation of Turner syndrome is called mosaic Turner syndrome. This occurs when a female is missing one copy of the X chromosome in just some of her cells.
The third genetic pattern of Turner syndrome occurs when a female has a mutated, or abnormal, X chromosome in all of her cells.
Random occurrence: Although Turner syndrome is a genetic disorder, it is not inherited or passed down among families. Instead, the genetic changes appear to occur randomly. To date, researchers have not discovered exactly what causes this to happen.