Alternative Names
45, X; Monosomy X; TS; Turner's Syndrome; Ullrich-Turner syndrome; Monosomy X syndrome
Symptoms & Characteristics
Turner syndrome (also known as 45, X) is a chromosomal condition that affects development in females. The features of Turner syndrome can include:
- short stature (typically becomes evident by 5 years old)
- extra folds of skin on the neck (called webbed neck)
- low hairline at the back of the neck
- puffiness or swelling (called lymphedema) of the hands and feet
- skeletal abnormalities (such as a broad/flat chest and scoliosis)
Females with Turner syndrome also experience early loss of ovarian function (called premature ovarian failure). The ovaries develop normally at first, but egg cells (called oocytes) usually die prematurely and most ovarian tissue degenerates before birth. Many affected girls do not undergo puberty unless they are treated with the hormone estrogen. A small percentage of females affected with Turner syndrome retain normal ovarian function through young adulthood
Most girls and women affected with Turner syndrome have normal intelligence. Developmental delays, nonverbal learning disabilities, and behavioral problems are possible, although these characteristics vary among affected individuals.
Treatment
There is no cure for Turner syndrome. However, early diagnosis, routine surveillance and treatment can help to manage some of the symptoms.
How Common Is It?
About 1 in 2,000 female births worldwide are affected with Turner syndrome. However, Turner syndrome is much more common among pregnancies that do not survive to term (i.e. miscarriages and stillbirths).
Genetics & Inheritance
All of our genes are packaged together on chromosomes. People typically have 46 chromosomes in total, which are grouped into 23 pairs. The first 22 pairs are numbered largest to smallest (1-22) and are called autosomes. The last pair are called the sex chromosomes and determine gender, either XX (female) or XY (male). We typically inherit 23 chromosomes (one of each pair) from our mother (in an egg cell) and the other 23 from father (in a sperm cell).
Turner syndrome is related to the X chromosome. Turner syndrome results when one normal X chromosome is present in a female's cells and the other sex chromosome is either completely (or partially) missing or structurally altered.
About 50% of women with Turner syndrome have monosomy X (written as 45, X), which means that every cell in their body has only one copy of the X chromosome.
- 45, X is caused by a missing X in females, which occurs as a result of a random "non-disjunction event" in the formation of either the egg or sperm cell. Non-disjunction occurs when chromosomes in the developing egg or sperm fail to separate during cell division.The result is a sperm or egg cell with either an extra chromosome or one that lacks a chromosome. When this sperm or egg cell combines with one from the opposite sex, the resulting embryo will have cells with an extra chromosome (47) or cells that have a missing chromosome (45).
Turner syndrome can also occur if one of the sex chromosomes is partially missing or rearranged (structurally altered) rather than completely absent.
In addition, some people affected with Turner syndrome have a chromosomal change in only some of their cells, which is known as mosaicism. People affected with Turner syndrome caused by X chromosome mosaicism are said to have mosaic Turner syndrome.
- Mosaic Turner syndrome occurs as a random event during cell division in early fetal development (post-conception). As a result, some of an affected person's cells have the usual two sex chromosomes (either two X chromosomes or one X chromosome and one Y chromosome), and other cells have only one copy of the X chromosome (written as 46,XX/ 45,X and 46,XY/ 45,X, respectively).
There are other genetic conditions that have symptoms that overlap with Turner syndrome. A genetic consultation with a trained genetic professional is important for a complete evaluation, accurate diagnosis, as well as discussion of the benefits and limitations of chromosome testing and recurrence risk.
Genetic Testing
Turner syndrome can be diagnosed by a chromosome analysis, which is available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
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