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(Monosomy X; Gonadal Dysgenesis)
In Turner syndrome, 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.
Turner syndrome occurs in about 1 out of 4,000 live female births and is the most common sex chromosome abnormality in females. However, 99% of affected fetuses abort spontaneously.
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. 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 dysplasia of the hip (see Limb and Joint Defects). 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, and labia remain childlike rather than undergoing the changes of puberty. In 90% of girls, the ovaries are replaced by connective tissue and do not contain developing eggs (gonadal dysgenesis). A girl or woman with Turner syndrome is virtually always short compared with family members, and obesity is common.
Other disorders often develop. Heart defects include narrowing of part of the aorta (coarctation of the aorta—see see Coarctation of the Aorta). 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 and inflammation of the thyroid gland occur more frequently among girls with Turner syndrome than among the general population.
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 if a newborn has lymphedema or a webbed neck. However, they may not suspect the syndrome until adolescence, when the girl is short and does not mature sexually. Analysis of the chromosomes confirms the diagnosis. Doctors do ultrasonography or magnetic resonance imaging (MRI) of the heart to detect heart problems.
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. Estrogen replacement therapy is usually needed to initiate puberty and is typically given at age 12 to 13. Treatment with the female hormone estrogen (given in the form of birth control pills) is usually not started until after satisfactory growth has been achieved. Once satisfactory growth has been achieved, treatment with growth hormone is stopped. Estrogen treatment may improve the girl’s ability to plan tasks, pay attention, and assess visual and spatial relationships as well as stimulate sexual maturation. Continuation of estrogen replacement therapy helps the bones become dense and helps the skeleton develop properly.
Children with this syndrome should have regular heart examinations, kidney function tests, hearing examinations, bone evaluations (for disorders of the hips and spine), eye examinations by a pediatric ophthalmologist, thyroid function tests, and screening tests for celiac disease. Blood tests for glucose (sugar) intolerance may be done in adulthood.
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