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Turner Syndrome (TS)
Saturday, 26 July 2003
Wednesday, 18 February 2004
Turner Syndrome (TS) is a genetic condition most commonly caused by the presence of a single X chromosome in a person’s genetic make-up or “genotype.” Thus, instead of the normal 46 chromosomes, which include a pair of sex chromosomes, these individuals have 45 chromosomes and only have a single X (sex) chromosome and the condition is called 45,X in the medical literature. Turner syndrome patients are female and usually have a characteristic “phenotype” or physical appearance that includes short stature, immature internal sexual organs and lack of secondary sexual characteristics, as well as a pattern of major and minor malformations.
Only girls have Turner Syndrome and it occurs in about 1 out of 1,500-2,500 live born females. It occurs in any ethnic population.
Signs and Symptoms
Often, girls with TS have few noticeable major defects until puberty. At this time, these girls fail to undergo the normal adolescent growth spurt. Lacking ovaries, they do not usually develop breasts (secondary sexual characteristic). However, a small number of TS females do have enough ovarian development to have menstrual periods (menarche) and a small number do conceive and have children. Naturally, the phenotype (physical appearance) of the individual often leads to the diagnosis of TS. The diagnosis can be made at any age, including prenatally.
In fetuses, TS can be suspected by ultrasound if the following features are seen:
Thickening of the neck folds, responsible for the web-like appearance of the neck later in life;
Frank nuchal cystic hygromas, which is a sac containing lymphatic fluid in the neck;
Mild shortness of the femur (upper leg) bone at midtrimester.
In infants, TS can be diagnosed by the following physical findings:
Low birth weight and decreased length.
Loose neck skin (pterygium colli) and edema of the hands and feet
Flattened middle region of the face and redundant skin around the eyes
Nipples appearing widely spaced
Heart and cardiovascular system: heart murmur (due to aortic stenosis or bicuspid aortic valve) or decreased pulses in the groin (due to aortic coarctation)
Kidney: structural defects such as incorrect location in the body or misshapen kidneys, detected on ultrasound.
In older children, diagnosis is often made by:
Slow growth and proportionate short stature
Delayed or absent periods (menses)
Webbing of the neck, a low hairline on the back of the neck, small jaw, prominent ears, high arched palate in the mouth, and rounded fingernails
Not all individuals with TS reveal the same karyotype. There is variation in the chromosomal abnormality, which is why there is great variability in physical appearance. However, about 50% of cases of TS are caused by the 45,X karyotype, indicating that only one X chromosome is inherited. The single X is of maternal origin in 70-80% of patients; however, the mechanism of chromosome loss is unknown and the risk for the syndrome does not increase with maternal age. About 30-40% are mosaic, which means that the mutation occurs in some but not all of the cells of the body. Mosaic Turner syndrome can vary in severity since the fewer the cells of the body affected, the milder the disease.
In order to confidently diagnose TS, laboratory tests and imaging studies are obtained. A karyotype is performed in all suspected cases of TS. A karyotype consists of a picture of all the chromosomes, and in TS only one X chromosome instead of two is found. In addition, endocrine evaluations are performed in older patients with short stature or lack of menstruation. If learning disabilities are suspected, psychometric evaluations may be performed. These measure psychological variables, such as intelligence, aptitude, behavior, and emotional reactions. Although intelligence is usually normal, females with TS have been observed to show a reduced ability to interpret spatial relationships.
Because TS involves many different parts of the body, the child will usually have more than one doctor. The child will have a primary care doctor as well as specialists in order to best address specific problems and provide the child with the best overall treatment. For example, the heart, kidneys and thyroid gland are often evaluated regularly. Other specific concerns include developmental delays, learning disabilities, slow growth, and amenorrhea (lack of menstruation).
Recombinant human growth hormone therapy may be given to increase height. This therapy has been shown to be effective in most but not all children. Some doctors believe that growth hormone treatment should be started in early childhood, while other doctors wait until there is specific evidence of slow growth before starting therapy. Estrogen replacement therapy is sometimes started in early adolescence to help with puberty, but not everyone agrees about the best age at which to start treatment. The psychological preparedness of the child to accept therapy must be taken into account. For example, estrogen can lead to slowing of height growth. Thus, careful consideration should be given to the psychological consequences of delaying estrogen therapy for the purpose of achieving better adult height. The availability of very low dose estrogen replacement therapy in the future may minimize the need to choose between appropriate pubertal replacement and optimizing height potential. Psychosocial support for these girls is an integral component of treatment. Some experts believe it is best to advise the child between the age of 8 and adolescence that she will probably not have children. However, successful pregnancies have been carried to term using ovum donation and in vitro fertilization.
Careful and appropriate health maintenance should be continued for girls with TS throughout their lifetimes. This chromosome abnormality is associated with numerous medical problems in addition to the lack of sexual maturity. In the absence of severe heart defects at birth, most girls with TS survive into adulthood and have normal intelligence. About 2-5% of women with Turner syndrome have some ovarian function. They may spontaneously start menstruating and can then become pregnant. As mentioned above, women with TS may have children via alternatives such as in-vitro fertilization and embryo transfer.
As with many childhood diseases, psychological problems may result from the stigma associated with the condition and its symptoms. These can be addressed early to minimize long-term effects on emotional development and overall health and wellness. In adult women with TS, there seems to be a high prevalence of bone mineral density, lipid, and thyroid abnormalities. These women have a tendency toward obesity, elevated blood pressure, and diabetes mellitus. The outcomes are highly variable and depend on the individual. Of course, proper health care over the course of one’s lifetime is essential to achieving the best prognosis. Many females with TS lead relatively normal lives, although coupled with long-term health management.
Connect with other parents
In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.
http://turnersyndrome.org/ Turner Syndrome Society of the United States
A great website committed to providing support to individuals with Turner Syndrome, as well as advancing research into this condition and promoting education and learning.
This site does a thorough job in explaining some of the basics of Turner Syndrome. It includes a diagram of a karyotype and illustrates the abnormality involving the sex chromosomes (the 23rd pair). It also provides information on ongoing clinical trials.
Turner Syndrome Support Society
A great site wich is dedicated to providing support for anyone affected by the Syndrome.
National Institute of Child Health and Development
This site provides general information about Turner syndrome, as well as sharing information about clinical studies of Turner Syndrome being conducted at the NIH.