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Turner syndrome

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Definition:

Turner syndrome is a genetic condition that occurs only in females. Female cells normally have two X chromosomes. In Turner syndrome, cells are missing all or part of an X chromosome.

Alternative Names:

Bonnevie-Ullrich syndrome; Gonadal dysgenesis; Monosomy X

Causes, incidence, and risk factors:

Humans have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. Two of these chromosomes, the sex chromosomes, determine if you become a boy or a girl. Females have two of the same sex chromosomes, written as XX. Males have an X and a Y chromosome (written as XY).

In Turner syndrome, a female does not have the usual pair of two complete X chromosomes. Most commonly, the female patient has only one X chromosome. Others may have two X chromosomes, but one of them is incomplete. Sometimes, a female has some cells with two X chromosomes, but other cells have only one.

Turner syndrome occurs in about 1 out of 2,000 live births.

• Review Date: 12/11/2006
• Reviewed By: Brian Kirmse, MD, Mount Sinai School of Medicine, Department of Human Genetics, New York, NY. Review provided by VeriMed Healthcare Network.

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