Turner syndrome (monosomy X or TS) is a genetic disorder that occurs in girls. It causes a variety of traits and problems. Girls with TS are shorter than most girls. They don’t go through normal puberty as they grow into adulthood. They may also have other health problems such as heart or kidney problems. The seriousness of these problems varies from girl to girl. Many of the health problems affecting girls with Turner syndrome can be managed or fixed with treatment. Turner syndrome occurs in about 1 in 2,000 to 2,500 girl babies.
When a baby is conceived, a normal egg cell and normal sperm cell start with 46 chromosomes. The egg and sperm cells then divide in half. The egg and sperm cells then have 23 chromosomes each. When a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes, the baby will then have a complete set of 46 chromosomes, or 23 pairs. Half are from the father and half are from the mother. The 23rd pair is called the sex chromosomes. In females, the 23rd pair is two X chromosomes. In males, the 23rd pair is one X and one Y chromosome.
There are 2 types of Turner syndrome: monosomy X TS and mosaic TS. About half of all girls with Turner syndrome have a monosomy disorder. Monosomy means that a person is missing one chromosome in the pair. Instead of 46 chromosomes, the person has only 45 chromosomes. This means a girl with TS has only one X chromosome in her 23rd pair. Sometimes an error occurs when an egg or sperm cell is forming, causing it to have a missing sex chromosome. But it is usually an error that happened by chance when the father's sperm cell was forming. The missing sex chromosome error can occur in either the mother's egg cell or the father's sperm cell.
Girls with mosaic TS have chromosome changes in only some cells, but not all cells. A small number of cases have the normal number of 46 chromosomes, but with part of the X chromosome missing. When only part of an X chromosome is missing (deletion), a girl with the syndrome will usually have milder signs of TS. The features of TS depend on which part of the X chromosome is missing.
During a pregnancy, the healthcare provider may have seen a structure called a cystic hygroma during a fetal ultrasound. A cystic hygroma is a fluid-filled sac at the base of the neck. It often goes away before birth. But sometimes the sac is there when the baby is born.
About 50% of girls born with TS will have puffy hands and feet at birth. They will also have a wide neck with folds of skin down the sides of the neck (called webbing). Girls with TS often also have:
Chromosome problems such as TS can often be diagnosed before birth. This is done by looking at cells in the amniotic fluid or from the placenta. This can also be done by looking at the amount of the baby’s DNA in the mother's blood. This is a noninvasive prenatal screening. These tests are very accurate.
Fetal ultrasound during pregnancy can also show the possibility of Turner syndrome. But ultrasound is not 100% accurate. Problems due to the disorder may not be seen with ultrasound.
If a healthcare provider thinks that your newborn baby girl may have TS, he or she will usually take a small sample of your baby’s blood. The lab will look at the sample to see if 1 X sex chromosome is missing.
The healthcare provider may refer you to a genetic counselor. This expert can explain the results of chromosome tests, as well as tests available to diagnose chromosome problems before a baby is born.
Sometimes a girl with TS doesn’t have any problems as a baby or child. It’s only when she doesn’t go through puberty or is shorter than her peers that her healthcare provider may suspect TS.
There is no cure for TS. But many of the more serious problems can be treated. For example, growth hormone and androgen therapy can increase the final adult height of a girl. She can also take hormone therapy to develop secondary sex traits such as breasts, pubic hair, and underarm hair. Surgery can fix coarctation of the aorta, if needed. And medicines are available to treat high blood pressure, diabetes, and thyroid problems. A woman with TS can have children by using donor eggs.
Being shorter than normal is the most common feature of TS as a girl grows. The average adult height of a woman with TS is 4 feet, 8 inches. A girl may also have cubitus valgus. This means that when she stands with her arms at her side, her elbows will be slightly bent. She can’t keep her arms perfectly straight at her side.
Most women with TS are born with poorly formed or missing ovaries. Ovaries make estrogen, and without it, a girl with TS will not develop sexually. The usual signs of puberty don’t happen unless the girl is given hormone therapy. This includes breast development, menstrual periods, and growth of pubic hair and hair elsewhere on the body. Most girls with the syndrome won’t be able to have children (are infertile) as adults.
Other common problems with TS affect the heart, kidney, and thyroid. About 1 in 10 girls with TS is born with coarctation of the aorta. This means the main artery that leaves the heart is narrowed. This problem sometimes needs to be fixed with surgery.
Girls with TS generally have normal intelligence. They tend to score higher on their verbal IQ than their nonverbal IQ. But they may have problems in the areas of spatial perception. They may also have certain learning disabilities.
Other possible problems include:
Researchers don’t know how to prevent the chromosome error that causes this disorder. In general, a woman who has a child with Turner syndrome is not at increased risk of having another baby with the condition. TS is usually not inherited in families but happens randomly.
If your baby girl is born with TS, there are things you can do to take care of yourself and your baby.
Call the healthcare provider if your child has:
Tips to help you get the most from a visit to your child’s healthcare provider:
Article Last Updated: August 11, 2020
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