Turner syndrome is a genetic disease.  It is most commonly caused when a fertilized egg has only a single "X" chromosome. As such, all Turner's patients are without a "Y" chromosome and develop as females. 

It is fairly rare, occuring in about 1 in 2,000-5,000 live births, although it is estimated that approximately 99% of eggs with a single X chromosome will result in a miscarriage.  In addition, the symptoms can be subtle and often are not noticed until the patient is near adulthood.  These include short stature, swelling, a broad chest, a low hairline, low set ears and a webbed neck.  Patients also do not develop ovaries and are sterile,

Turners patients suffer from numerous complications including heart disease, hypothyroidismdiabetes mellitus, vision problems and hearing problems.  They also frequently suffer from autoimmune diseases.

If recognized early enough, Turner patients can be given human growth hormone to increase their height and estrogen to develop secondary sexual characteristics and to offset osteoporosis.

Turner syndrome at Wikipedia

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