Turner Syndrome (45 X Syndrome)
Turner Syndrome is caused by a missing sex chromosome. Typically, most people have 46 chromosomes in 23 pairs; 22 of these pairs are the same in both males and females. The 23rd pair is called the sex chromosomes and these determine whether a person will be born with the physical features of a male (46, XY) or a female (46, XX). In Turner Syndrome (TS), the most common chromosome configuration is 45, X. This means that the person is missing a sex chromosome, either an X or a Y. People with Turner Syndrome are all physically female.
Turner syndrome occurs in 1 in 2000 to 1 in 2500 live female births.
Common Associated Conditions
Girls with Turner syndrome may have all or some of the following physical features:
- short stature (usually under 5' tall) is the most common feature of TS
- narrow, high-arched palate (the roof of the mouth is higher and narrower than is typical)
- retrognathia (the lower jaw is small)
- ears protruding outward, and/or low set, and/ or rotated toward the neck
- webbed neck (excess or stretched skin) which may include a lowered hairline in the back
- droopy eyes
- strabismus (lazy eye)
- broad chest
- cubitus valgus (arm turns slightly out at the elbow when the arm is extended)
- scoliosis (curvature of spine)
- flat feet
- small and narrow fingernails, toenails that turn up
- short fourth metacarpal (bone in hand between the knuckle of the fourth finger and the wrist)
- edema (swelling or puffiness) or hands and feet, especially at birth
Short Term Treatment and Outcomes
If a girl is suspected of having Turner Syndrome, either because of testing done before she was born or because she has physical features that suggest this diagnosis, a chromosome test using a blood sample should be done to confirm the diagnosis.
Girls with Turner Syndrome have about a 50% chance of having specific congenital heart conditions (features of the heart and circulatory system that are present at birth and affect how well the heart and the rest of the circulatory system pump blood around the body). The most common congenital heart conditions in girls with Turner syndrome include
- coarctation of the aorta (a narrowing of the large artery that leads out of the heart and carries blood to the rest of the body);
- a bicuspid aortic valve (two valve leaflets instead of three between the largest artery in the body, the aorta, and the left ventricle of the heart) in the heart;
- partial anomalous pulmonary venous return (a misalignment of some of the major vessels entering or coming off of the heart).
Although these congenital heart conditions may cause problems in early life, some girls who have them may not have any problems until they are older. Every girl who is diagnosed as having Turner syndrome should be evaluated by a pediatric cardiologist (children's heart doctor) who is familiar with the cardiovascular features that are more likely to be present in girls with Turner syndrome.
Some 30% to 40% of individuals will have problems with their kidneys and/or urinary tract. Once a diagnosis of Turner syndrome is made, the urinary system should be checked for any clinically relevant problem.
Short stature is the most common feature in Turner syndrome and this feature becomes more prominent over time. Even when a girl with Turner Syndrome is still a baby, parents may wish to discuss growth hormone therapy with their daughter's care providers to become familiar with the pros and cons of treatment and to plan if or when treatment might begin. This therapy is typically managed by a pediatric endocrinologist (children's doctor who manages hormonal conditions). Many girls begin to show short stature as early as the first two or three years of life. If left unattended, women with Turner syndrome will average 20 cm (almost 8 inches) shorter than their peers without Turner syndrome. Although not deficient in growth hormone, treatment with additional growth hormone serves to increase the growth rate and final stature. In one study, treatment with growth hormone resulted in a final stature that was over seven centimeters (almost 3 inches) taller than girls not treated with growth hormone. The average length of treatment was 5.7 years. In addition, the girls who were youngest when growth hormone therapy was started, were tallest at the start of treatment and those who had the tallest parents had the most marked response to this therapy.
Long-Term Treatment and Outcomes
As a woman with Turner Syndrome ages, she needs to be followed to watch for other health conditions that may develop over time. Over time, the aorta (the main artery that comes off of the heart and carries blood to the rest of the body) may start to stretch out and dilate in up to 30% of women with Turner syndrome. If this should occur, the rate of dilation should be monitored by a cardiologist. A dilated aorta is a risk factor for aortic dissection, which means that the walls of this large blood vessel can weaken and give way suddenly, resulting in very serious damage. This serious complication is rare and only occurs in about 1% of adults. As hypertension (elevated blood pressure) may be a factor in aortic enlargement and since it is fairly common in individuals with Turner syndrome, it is very important to monitor blood pressure and control any hypertension that may develop.
There is also an increased incidence in electrocardiographic (EKG) features in individuals that may not be associated with any structural heart defects. The clinical significance of these changes is unclear, but may warrant additional monitoring by electrocardiogram and follow up by a cardiologist.
Although up to one third of girls with Turner syndrome may have some normal pubertal development, only a small percentage will have menstrual periods due to the failure of the ovaries to produce sufficient estrogen. Estrogen replacement therapy should be guided by a pediatric endocrinologist to allow the development of secondary sex characteristics to take place and to support appropriate mineralization of bones. Most women with Turner syndrome will be very unlikely to spontaneously get pregnant because of the characteristic ovarian dysfunction, but there may be interventions that will allow a woman with Turner syndrome to carry a pregnancy. The potential options for reproduction should be guided by a team made up of her primary care provider, her endocrinologist, her obstetrician, and her cardiologist and put into the context of any other clinically relevant features she may have.
Implications for Children's Development
People with Turner Syndrome have intelligence quotients (I.Q.s) that mirror the spectrum seen in the general population. In other words, most people with Turner Syndrome have normal intelligence. However, there is a greater likelihood of having a learning disability, especially with spatial-temporal processing (imagining objects in relation to each other), nonverbal memory and attention.
Hearing loss may be a feature of Turner syndrome, so an evaluation by an otolaryngologist (an ear nose and throat doctor) and audiologist to identify any hearing problems is recommended for all affected individuals. Girls with Turner syndrome are also more likely to have otitis media (infection of the middle ear), which may also affect hearing.
Genetics Home Reference. Turner Syndrome Accessed 3/1/2016
45X Syndrome in Jones, KL (2008) Smith's Recognizable Patterns of Human Malformation, 6th Edition. Elsevier Saunders, Philadelphia. pp 76-81