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Turner syndrome

  • Definition

    Turner syndrome is a genetic condition in which a female does not have the usual pair of two X chromosomes.

    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 normally have two of the same sex chromosomes, written as XX. Males have an X and a Y chromosome (written as XY).

    In Turner syndrome, cells are missing all or part of an X chromosome. The condition only occurs in females. 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.