Triple X syndrome

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Definition

Triple X syndrome is an abnormality of the chromosomes that affects about one in 1,000 females. Females normally have two X chromosomes, one from each parent. In triple X syndrome, a female has three X chromosomes — hence, the name.

Triple X syndrome isn't inherited. It usually results from a mistake in the formation of a mother's egg cell or a father's sperm cell. Sometimes, triple X syndrome occurs as a result of an error early in the embryo's development.

If your daughter has triple X syndrome, know that many cases result in no symptoms or only mild symptoms. In other cases, symptoms may be more pronounced — possibly including developmental delays.

Treatment for triple X syndrome depends on which symptoms your daughter exhibits and their severity.

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Symptoms