Chromosome Disorders

Turner's (Turner) Syndrome

Turner's syndrome (also called Turner syndrome) occurs when there is only one X chromosome, and the pattern is designated X0, with a zero standing in for the missing chromosome. At least one X chromosome is necessary for an embryo to be viable. An embryo with only one Y for the sex chromosome will not survive. Turner's syndrome is estimated to occur in about one of every 2,500 to 4,000 female births, with the infant appearing female at birth. The average age of diagnosis is 6.6 years, although it may not be diagnosed until much later in life. The ovaries do not fully develop and thus do not produce a normal level of estrogen. This lack of estrogen means that the individual will not go through puberty and menstruate. A female with Turner's syndrome is short, usually less than 5 feet tall, and has immature breasts. She is also likely to suffer some degree of mental retardation and be hyperactive. The person with Turner's syndrome often experiences social isolation because of her body image and poor self-concept. She may receive estrogen and progesterone during puberty to enhance sex characteristics, and this can produce a menstrual flow, as the uterus is fully formed. Androgens may also be given at this time to promote height. The earlier Turner's syndrome is detected, the more likely treatments will be effective. The Turner's syndrome female usually has a strong feminine gender identity and a strong interest in motherhood. Although she is infertile due to the lack of functioning ovaries, she can become pregnant through in vitro fertilization and deliver via cesarean section.

Klinefelter's Syndrome

The most common sex chromosome disorder is Klinefelter's syndrome, in which the male has an extra X chromosome and is designated XXY. It is estimated to occur in 1 out of every 500 to 1,000 male births. While the Y triggers the development of male geni-talia, the extra X prevents full development. Internally, the genitalia of individuals are like a normal male's, though the testes and penis are small. They cannot produce sperm and are sterile. Individuals also have low testosterone levels and low sexual desire. They may have gynecomastia (abnormal breast development in a male), a feminized body shape, be tall, and lack fully developed secondary sex characteristics, such as facial and body hair. Testosterone therapy can help develop the secondary sex characteristics, especially during puberty. With Klinefelter's syndrome, there is an increased chance of developmental disabilities and mental retardation, particularly speech and language difficulties. As with Turner's syndrome, treatment is usually most successful when started early. The individual with Klinefelter's syndrome typically has a male gender identity.

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