Turner syndrome (TS) is a chromosomal condition that describes girls and women with common features that are caused by complete or partial absence of the second sex chromosome. The syndrome is named after Dr. Henry Turner, who was among the first to describe its features in the 1930's. TS occurs in approximately 1 of 2,000 female's born and in as many as 10% of all miscarriages.
Females normally have two X chromosomes (46,XX) and males have one X and one Y (46,XY). Turner syndrome individuals are missing all or part of one of their sex chromosomes.
About half of girls with Turner syndrome have only one X chromosome (45,X). Another third have two X chromosomes, but part of one X is missing. Other individuals with Turner syndrome have a mosaic pattern: some of their cells are missing an X chromosome (45,X), while other cells have different chromosome composition (such as 46,XX).
Diagnosis is made through a test called a karyotype, which is usually performed on cells in the amniotic fluid before birth and on cells in the blood after birth. A trained specialist counts the chromosomes in the white blood cells and looks for abnormalities.
Turner syndrome may be diagnosed throughout the life span, including adulthood, if signs are subtle. Signs that indicate a karyotype is needed can include:
- Fetal abnormalities such as cystic hygroma (fluid around the neck)
- Webbed neck (excess skin) or lymphedema (swelling of hands and feet) in newborns
- Specific heart problems in infants
- Slow growth and/or short stature
- Delayed puberty or amenorrhea (lack of menstrual cycles)
- Infertility or menstrual irregularities.
Primary characteristics of Turner Syndrome
Short stature. The most common feature of Turner syndrome is short stature. The average height of an adult TS woman who has not received human growth hormone treatment is 4’8”. Individuals tend to be a little shorter at birth, averaging 18.5” compared to an average of 20” for all girls. Growth failure continues after birth, and most girls with TS fall below the normal female growth curve for height during early childhood. TS girls who are not treated with hormone replacement usually do not have a pubertal growth spurt; many will continue to grow at a slow rate until they are in their twenties. Many girls who undergo growth hormone treatment have been able to achieve adult height within the lower range of normal.
Premature ovarian failure. Most (90%) TS individuals will experience early ovarian failure. In the general population, the ovaries produce eggs and hormones necessary for the development of secondary sexual characteristics. Estrogen replacement therapy is necessary for breast development, feminine body contours, menstruation and proper bone development. About a third of TS individuals will show some signs of breast development without estrogen treatment; however, many will not complete puberty, and those that do often have premature ovarian failure. Therefore, the majority of individuals will require estrogen from puberty until the normal age of menopause. Fertility without assisted reproduction therapy is rare (less than 1%).
Physical features. Many characteristic features are associated with Turner syndrome. Their presence and severity vary greatly from individual to individual.
- Narrow, high-arched palate (roof of the mouth)
- Retrognathia (receding lower jaw)
- Low-set ears
- Low hairline (the hair on the neck is closer to the shoulders)
- Webbed neck (excess or stretched skin)
- Slight droop to eyes
- Strabismus (lazy eye)
- Broad chest
- Cubitus valgus (arms that turn out slightly at the elbows)
- Scoliosis (curvature of the spine)
- Flat feet
- Small, narrow fingernails and toenails that turn up (usually if lymphodema was present at birth)
- Short fourth metacarpals (the ends of these bones form the knuckles)
- Edema (swelling) of hands and feet, especially at birth
Intelligence. TS individuals are on average of normal overall intelligence with the same variance as the general population. They do, however, often have difficulty with spatial-temporal processing (imagining objects in relation to each other), nonverbal memory and attention. This may cause problems with math, sense of direction, manual dexterity and social skills. New and better ways to compensate for these problems, which currently fall under the general category of nonverbal learning disabilities, are being researched.
Risks associated with Turner Syndrome
Several medical problems occur more frequently in individuals with Turner syndrome than in the general population. It is important that TS individuals are screened regularly to see if any of these problems exist. Most of these conditions can be managed successfully with good medical care.
Heart. Some form of cardiac abnormality occurs in approximately one-third of TS patients. Problems are primarily left-sided and may include:
- coarctation (narrowing) of the aorta and bicuspid aortic valve (a valve with two leaflets instead of the usual three).
- TS individuals are also at higher risk for hypertensionor high blood pressure.
- TS patients should receive an echocardiogram or MRI to evaluate the heart at the time of diagnosis regardless of age and have their heart re-evaluated periodically for aortic root enlargement.
- All individuals with TS should be aware of the symptoms of dissection of the aorta, an uncommon but life-threatening complication. These include sudden, severe, sharp, stabbing, tearing, or ripping chest pain, intense anxiety, rapid pulse, profuse sweating, nausea and vomiting, dizziness, fainting or shortness of breath.
Kidney. Thirty percent of TS individuals will have kidney abnormalities. Many of the abnormalities do not cause any medical problems; however, some may result in urinary tract infections and an increased risk of hypertension. It is recommended that TS individuals receive a renal ultrasound examination at the time of diagnosis.
Thyroid. Hypothyroidism (low level of thyroid hormone) caused by autoimmune thyroiditis (inflammation of thyroid gland) occurs frequently in individuals with TS. It can be diagnosed with a blood test and is easily treated with thyroid hormone.
Ears. Otitis media (ear infection) is extremely common in TS girls particularly in infancy and early childhood. Aggressive treatment of infections is appropriate. The majority (50-90%) of TS women will also develop early sensorineural (nerve) hearing loss and may require hearing aids earlier than the general population.
Treatment of Turner Syndrome
The treatment of TS individuals should be individualized; physicians, family and patients should decide on treatment options together.
Growth hormone therapy. Human growth hormone (hGH) is an FDA-approved drug used to increase the growth rate and achieve greater final height in TS patients. Therapy should be considered when a TS individual experiences growth failure and/or drops below the 5th percentile of the normal female growth curve. The expected increase in height depends upon many factors, including how early GH is started, what dose is given, the duration of treatment, if anabolic steroids (such as oxandrolone) are also given, and how late estrogen therapy is begun. Gains in height between 5 and 16 cm (2 and 6 inches) have recently been reported; however, not every individual responds to growth hormone. Treatment is discontinued when growth is very slow(less than 2 cm or 1 inch per year) or if the patient has reached a satisfactory height.
Estrogen therapy. This therapy is necessary in most TS individuals because of ovarian failure. Therapy is typically started at 12-14 years of age but should be individualized to optimize both growth and pubertal development. Estrogen is given in small doses to initiate puberty and breast development. The dose is then increased and progesterone is added in order to initiate a monthly menstrual cycle. TS individuals can experience normal sexual function on estrogen therapy. Because of the role estrogen plays in maintaining healthy bone mass, it is generally recommended that the therapy continue until the age of normal menopause (approximately 50 years of age).
Becoming a family
Many options are available to TS women who wish to have children. The most common fertility solution for TS women is adoption. At this time, assisted reproduction technology options for TS women who wish to become pregnant is discouraged from specific medial specialists due to the increased rate of mortality related to cardiac issues. The reproductive technology options include in-vitro fertilization with egg donation by a related or anonymous donor or donor embryo transfer. It is critical that a TS patient undergo a thorough physical evaluation (particularly cardiac and renal) before attempting pregnancy and include a high risk prenatal physician from the onset of pregnancy.
It's important to note that many women consider their "family" as an extension of relatives, nieces, nephews, and neighbors. Some women with TS, as other women in the United States are happy without having children.
With the help of medical specialists and a good social support system, a woman with Turner syndrome has many choices that will enable her to live a happy, healthy life.