Triple X syndrome, also called trisomy X, is a genetic disorder that affects about 1 in 1,000 females. Females normally have two X chromosomes in all cells — one X chromosome from each parent. In triple X syndrome, a female has three X chromosomes.

Many girls and women with triple X syndrome have no symptoms or only mild symptoms. In other cases, symptoms may be more pronounced — possibly including developmental delays and learning disabilities.

Treatment for triple X syndrome depends on which symptoms, if any, are present and their severity. Normal sexual development and the ability to have children are typical for most females who have triple X syndrome.