(Turner's Syndrome; Monosomy X; Gonadal Dysgenesis)
Turner syndrome is a sex chromosome abnormality in which girls are born with one of their two X chromosomes partially or completely missing.
Turner syndrome is caused by the deletion of or partial formation of one of the two X chromosomes.
Girls with the syndrome are typically short and have loose skin on the back of the neck, learning disabilities, and an inability to undergo puberty.
The diagnosis is confirmed by analyzing the chromosomes.
Treatment with hormones can stimulate growth and initiate puberty.
Chromosomes are structures within cells that contain DNA and many genes. A gene is a segment of deoxyribonucleic acid (DNA) and contains the code for a specific protein that functions in one or more types of cells in the body (see Genes and Chromosomes for a discussion about genetics). Genes contain instructions that determine how the body is supposed to function.
The sex chromosomes determine whether a fetus becomes male or female. A pair of X and Y chromosomes (XY) results in a male, and a pair of X and X chromosomes (XX) results in a female.
Turner syndrome occurs in about 1 out of 2,500 live female births. However, this chromosome abnormality is much more common at conception, but 99% of affected fetuses abort spontaneously.
Some symptoms of Turner syndrome are noticeable at birth. Other symptoms are not noticed until the children are school-age or older.
Many newborns with Turner syndrome are mildly affected, but some have swelling (lymphedema) on the backs of their hands and tops of their feet. Swelling or loose folds of skin are often evident over the back of the neck. Heart defects include narrowing of part of the aorta (coarctation of the aorta). Other abnormalities seen later include a webbed neck (wide skin attachment between the neck and shoulders) and a broad chest with widely spaced and inwardly turned nipples. Infants are at a higher risk of a problem with the hip joint called developmental dysplasia of the hip. Less common symptoms include drooping upper eyelids (ptosis), a low hairline at the back of the neck, moles (nevi), and poorly developed nails.
Girls with Turner syndrome generally do not have menstrual periods (amenorrhea), and the breasts, vagina, uterus, and labia remain childlike rather than undergoing the changes of puberty (delayed puberty). About 10% of adolescents have scoliosis. In 90% of girls, the ovaries are replaced by connective tissue and do not contain developing eggs (gonadal dysgenesis), so these girls are infertile. A girl or woman with Turner syndrome is often short compared with family members, and obesity is common.
Other disorders may develop. High blood pressure frequently occurs with aging even if the girl does not have coarctation. Kidney defects, diabetes mellitus, and thyroid diseases are common. Occasionally, abnormal blood vessels in the intestine cause bleeding. Hearing loss occurs, and crossed eyes (strabismus) and farsightedness (hyperopia) are common. Celiac disease, inflammation of the thyroid gland, and diabetes mellitus occur more frequently among girls with Turner syndrome than among the general population. There is an increased risk of an enlarged aorta so girls need to be screened regularly with echocardiography.
Many girls with Turner syndrome have attention-deficit/hyperactivity disorder and learning disabilities with difficulty assessing visual and spatial relationships, planning tasks, and paying attention. They tend to score poorly on certain performance tests and in mathematics, even if they achieve average or above-average scores on verbal intelligence tests. Intellectual disability is rare.
Doctors may suspect the diagnosis of Turner syndrome if a newborn has lymphedema or a webbed neck. However, they may not suspect the syndrome until adolescence, when the girl is short and has delayed puberty.
To confirm the diagnosis, the chromosomes are analyzed using a blood test.
There is no cure for Turner syndrome. However, some specific symptoms and problems caused by the syndrome can be treated. Coarctation of the aorta is usually repaired surgically. Doctors monitor and repair other heart defects as needed. Lymphedema can usually be controlled with support hosiery and other techniques such as massage.
Treatment with growth hormone can stimulate growth. Once satisfactory growth has been achieved, treatment with growth hormone is stopped.
Treatment with the female hormone estrogen is usually needed to initiate puberty and is typically given at age 12 to 13 but is usually not started until after satisfactory growth has been achieved. After girls have undergone puberty, they are given birth control pills that contain estrogen plus another female hormone, progestin. This hormone treatment helps girls maintain their female sexual characteristics. Estrogen treatment may also improve the girl’s ability to plan tasks, pay attention, and assess visual and spatial relationships and also helps the bones become dense and helps the skeleton develop properly.
Some girls who have Turner syndrome begin puberty normally without estrogen replacement therapy, but this is more common in girls who are mosaic. Girls who have mosaic Turner syndrome have a mixture of two types of cells. Some of the cells contain two X chromosomes and some cells contain just one X chromosome. Such girls may become pregnant if fertility treatments are used.
Girls with Turner syndrome should have regular evaluations to detect problems that may result from this disorder. Evaluations include the following: