Turner Syndrome

Turner Syndrome

This condition is a disorder of sexual development of women. It arises due to defective sexual differentiation at the time of fertilization. Turner syndrome is a genetic condition in which a female does not have the usual pair of two X chromosomes.

Humans have 46 chromosomes. Two of these chromosomes, the sex chromosomes, determine if you become a boy or a girl. Females normally have two of the same sex chromosomes, written as XX. Males have an X and a Y chromosome (written as XY).

In Turner syndrome, cells are missing all or part of an X chromosome. The condition only occurs in females. Most commonly, the female patient has only one X chromosome. Others may have two X chromosomes, but one of them is incomplete. Sometimes, a female has some cells with two X chromosomes, but other cells have only one.

About half of individuals with Turner syndrome have monosomy X, which means each cell in the individual’s body has only one copy of the X chromosome instead of the usual two sex chromosomes.Turner syndrome can also occur if one of the sex chromosomes is partially missing or rearranged rather than completely absent.Some women with Turner syndrome have a chromosomal change in only some of their cells, which is known as mosaicism. These are called mosaic Turner syndrome.Which all genes on the X chromosome are responsible for most of the features of Turner syndrome is still not fully understood. One gene called SHOX that is important for bone development and growth, and missing one copy of this gene is a likely causes for short stature and skeletal abnormalities in women with Turner syndrome.Most cases of Turner syndrome are not inherited. When this condition results from monosomy X, the chromosomal abnormality occurs as a random event during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction can result in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may lose a sex chromosome as a result of nondisjunction. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have a single X chromosome in each cell and will be missing the other sex chromosome.Mosaic Turner syndrome occurs as a random event during cell division in early fetal development. 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.

The incidence is estimated at 1 in 3000 newborn females.

Main features in this condition are absence of menstruation (Primary amenorrhea), incomplete development of sexual characters (sexual infantilism), short stature, multiple congenital abnormalities in women. After the time of expected puberty pubic and axillary hair remain sparse, the breasts are infantile, and no menses occur. In a small percentage of cases some menstruation may occur. Indeed, occasionally minimally affected women become pregnant; the reproductive life in such individuals is brief.

Main features:

Absence of menstruation. In this condition the egg cells in the ovaries usually die prematurely and most ovarian tissue degenerates before birth. A majority of the girls do not undergo puberty unless they are treated with the hormone estrogen. A small percentage of females with Turner syndrome do retain normal ovarian function.
After the time of expected puberty pubic and axillary hair remain sparse, the breasts are infantile, and no menses occur. In a small percentage of cases some menstruation may occur. Indeed, occasionally minimally affected women become pregnant; the reproductive life in such individuals is brief.
Incomplete development of sexual characters resulting to sexual infantilism.
Short stature, becomes evident at about the age of 5.
Multiple congenital abnormalities in women.
Webbed Neck is seen in about 30 percent of people. This is due to extra folds of skin on the neck.
A low hairline at the back of the neck.
Drooping of the eyelids
Ears are differently shaped. Ears are set lower on the sides of the head than usual.
Abnormal bone development especially the bones of the hands and elbows.
A larger than usual number of moles on the skin.
Puffiness or swelling (lymphedema) of the hands and feet.
Congenital heat diseases: coarctation of the aorta, the aortic valve defect.
Some girls with the condition may experience learning difficulties, particularly in math. Many have a difficult time with tasks that require skills such as map reading or visual organization. Many women with Turner syndrome have normal intelligence and some may have higher than average intelligence.

People with TS are all different. Some may have many physical abnormalities and symptoms, whereas others experience only a few medical problems. With early and appropriate medical care and ongoing support, many with TS can lead normal, healthy, and productive lives.

The diagnosis is made either at birth because of the associated anomalies or at puberty when amenorrhea and failure of sexual development are noted.The external genitalia are of female type but remain immature and do not grow as in adult females. There is no breast development. Internally the fallopian tubes and uterus are also immature. On the both sides the ovaries are grossly underdeveloped.Skeleton and the connective tissue are also involved. Swelling of the hands and feet, webbing of the neck, low hairline, skin folds on the back of the neck, a shield like chest with widely spaced nipples, and growth retardation. These features suggest the diagnosis in infancy. Ears may be deformed. A fishlike mouth, Eyes may show ptosis – drooping of the upper eye lids.

Other associated conditions which may be present in such patients are : Coarctation of Aorta, Renal malformations, tendency to keloid formation, hearing impairment, unexplained hypertension, tendency to diabetes, thyroid disease.

Treatment : At the anticipated time of puberty, replacement therapy with estrogen should be started. This helps in the maturation of the breasts, labia, vagina, uterus, and fallopian tubes. Linear growth and bone maturation rates are also improved by this treatment. But the eventual height rarely approaches the predicted level. Combination therapy with oxandrolone and/or growth hormone accelerates growth and increases final height.

Genetic Disorders