The Turner syndrome (XO syndrome) is a rare defect in sex chromosomes. The person is born with only one X chromosome (XO), and no matching X or Y sex chromosome. The sex chromosomes are named X and Y. Normally two X chromosomes (XX) occur in a female, and one of each (XY) in a male.
Patients look female, but are really asexual, as they do not develop testes or ovaries and are infertile. At puberty, the breasts and pubic hair fail to develop, the genitals remain childlike in appearance, and menstrual periods do not start. Other signs are short stature and a web of skin that runs from the base of the skull down the neck and onto the top of the shoulder.
Complications may include eye disorders (e.g. keratoconus), heart valve defects, narrowing of the aorta (main body artery), a stocky chest, the early development of diabetes and thin frail bones (osteoporosis).
The diagnosis can be confirmed by blood and cell tests that show the abnormal chromosome structure.
Female hormones (oestrogens) are given in a cyclical manner from the time of expected puberty to encourage the development of female characteristics, growth hormone can be used to improve height, and surgery can correct the heart defects and neck webbing.
Patients can function as females in every way except fertility, and can lead a normal life.