What is Turner syndrome (TS)?
Turner syndrome is a genetic disorder resulting in short stature and lack of puberty, along with several other medical issues. The severity of these problems varies among affected individuals. Typically, a female has two X chromosomes. Turner syndrome results from missing all or part of one of the X chromosomes. Turner syndrome occurs in 1 in 2,000 to 2,500 females.
The name "Turner syndrome" comes from Dr. Henry Turner, the physician who first described the collection of findings in 1938. It was not until 1959 that the cause of Turner syndrome was identified.
Normally during reproduction, a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes resulting in a complete set of 46 chromosomes, half from the father and half from the mother. Sometimes, an error occurs when an egg or sperm cell is forming, causing it to have a missing or abnormal sex chromosome. Turner syndrome occurs when either the egg or sperm fails to contribute a normal sex chromosome to the embryo, resulting in all or part of one of the X chromosomes being missing.
In some cases, the embryo may initially contain 46 chromosomes, however shortly after conception, the sex chromosomes do not divide properly, leaving a set of cells with only one X chromosome.
- About 50 percent of Turner syndrome results from missing an entire X chromosome.
- About one-third of girls with TS have the normal number of chromosomes (46 total), but they are missing a portion of the second X chromosome. In some cases, this is because the ends of the chromosome join together forming a ring; in other cases, the chromosome may be made up of two copies of the long (q) arm, and be missing the short, or p, arm. This is called an isochromosome.
When only part of an X chromosome is missing (called a deletion) the features of Turner syndrome that are present may vary depending upon which part of the X chromosome is missing.
Often, girls with Turner syndrome have a mosaic pattern (two or more chromosome patterns in the cells).
Related medical issues
Short stature is the most common feature of girls with Turner syndrome. The average adult height of a woman with Turner syndrome is 4 feet 8 inches, although some women reach 5 feet. Growth hormone therapy can be used in girls with Turner syndrome to increase their height.
Most girls with Turner syndrome have either poorly formed or absent ovaries. Ovaries produce estrogen and without estrogen, normal pubertal development does not occur. Signs of puberty, such as breast development and menstruation (periods), often do not occur without the help of hormone therapy.
Other medical issues
Other medical issues that can occur in girls with Turner syndrome include cardiac abnormalities, renal (kidney) abnormalities, hearing problems, skin disorders, dental/orthodontic issues and learning issues.
The diagnosis of Turner syndrome can be made in utero (during pregnancy), shortly after birth, during childhood or in the late teens.
Testing during pregnancy
In many cases, chromosomal abnormalities like those causing Turner syndrome can be diagnosed before a baby is born. This is done by analyzing cells in the amniotic fluid or from the placenta. A chromosome analysis, whether performed on a blood sample, cells from the amniotic fluid or the placenta, is over 99.9 percent accurate.
Fetal ultrasound during pregnancy can also give information about the possibility of Turner syndrome. However, ultrasounds are not 100 percent accurate, and many babies with Turner syndrome may look the same on ultrasound as those without Turner syndrome.
Sometimes features of TS are noted at birth which lead to the diagnosis of TS. When a girl is born with features suggestive of Turner syndrome, the healthcare provider usually takes a blood sample for chromosomal analysis (called a karyotype).
This confirms the diagnosis of Turner syndrome and determines the underlying chromosomal abnormality. Your healthcare provider may explain the results of the test to you or refer you to a geneticist or genetic counselor who can explain the results of chromosomal tests.
Sometimes a healthcare provider may recommend a chromosomal analysis as part of the workup for short stature if a girl’s height is noted to be less than what is expected for her age and family, and she is growing at a slower than expected rate.
Sometimes girls with Turner syndrome do not exhibit any signs of the condition as infants or children. It is only when they fail to go through puberty that a healthcare provider begins to suspect the diagnosis of Turner syndrome.
Risk of TS in future children
Although Turner syndrome is a genetic condition, in most cases it is not something that is inherited and not something that runs in families. Therefore, for most families, the chance of having another child with Turner syndrome is low.
Every pregnant woman has a risk for having a child with a chromosome abnormality that is associated with her age; as the woman gets older, this risk increases. The chance for having another baby with Turner syndrome is generally not increased above this population risk.
Your healthcare provider may refer you to a geneticist or genetic counselor who can explain what tests are available to diagnose chromosome problems before a baby is born.
There is no cure for Turner syndrome; however, many of the more serious problems can be treated. For example, growth hormone can be given to improve final height, and hormone replacement therapy can be given so that girls will develop signs of puberty.
Reviewed by: Denise Gruccio, CRNP; Holly Dubbs, MS, CGC
Date: July 2014