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During the earlier stages of embryonic development, a sex chromosome may be lost. This may result in certain cells in the growing body only getting one X chromosome. This is referred to as Mosaic Turner syndrome. In understanding the genetics of Mosaic Turner syndrome, we know that this genetic disorder stems from an incomplete or missing X chromosome. The mosaicism of this disorder comes from about 30 percent of patients only missing the X chromosome in some cells and not all. Those who have this disorder develop as females. This disorder affects about one in 2,000 live births.
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Genetics and Cause
In understanding the genetics of Mosaic Turner syndrome, we know it is usually caused by nondisjunction. This means that a pair of sex chromosomes did not separate during egg formation. This is not an inherited abnormality. In fact, women with this disorder are generally sterile. Only females are affected by this disorder.
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Signs and Symptoms
Young infants may present with a webbed and wide neck and swollen hands and feet. In older females, signs and symptoms may include:
- Flat, broad chest with a shield-like shape
- Dry eyes
- Absent menstrual periods
- Vaginal dryness, which may cause painful sexual intercourse
- Drooping eyelids
- Short height
- Incomplete or absent development at puberty, including small breasts and sparse pubic hair
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Making the Diagnosis
The doctor will usually begin by looking for signs of underdevelopment and performing a physical examination.
In some cases, this genetic disorder is diagnosed before the female is even born through prenatal testing with chromosome analysis.
Other testing may include echocardiogram, chest MRI, pelvic examination, karyotyping and an ultrasound of the kidneys and female reproductive organs. Karyotyping is a type of testing that can be done to examine a patient's chromosomes. Blood tests to check the levels of hormones are also often done and include follicle stimulating hormone and luteinizing hormone.
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Treating the Disorder
To help the child grow taller, growth hormone may be helpful. When the child is 12 or 13 years of age, estrogen replacement therapy is often started to help trigger the growth of pubic hair, breasts and other sexual characteristics. This genetic disorder does make women sterile. Infertility treatments will not reverse the issues with sterility. If a woman with this disorder wishes to have a child, she will have to use a donor egg.
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Complications may occur with this genetic disorder. These include arthritis, diabetes, heart defects, kidney problems, obesity, cataracts, Hashimoto's thyroiditis, high blood pressure, middle ear infections and scoliosis.
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The University of Utah Genetic Science Learning Center. (2011). Turner Syndrome. Retrieved on March 29, 2011 from The University of Utah Genetic Science Learning Center: http://learn.genetics.utah.edu/content/disorders/whataregd/turner/
PubMed Health. (2009). Turner Syndrome. Retrieved on March 29, 2011 from PubMed Health: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001417/