What is "triple x syndrome"

n. A form of chromosomal variation characterized by the presence of an extra X chromosome in each cell of a human female, sometimes leading to tall stature, learning disability, and/or epicanthic folds.

Triple X syndrome (also known as triplo-X, trisomy X, XXX syndrome, 47,XXX aneuploidy) is a form of chromosomal variation characterized by the presence of an extra X chromosome in each cell of a human female. A mosaic form also occurs where only a percentage of the body cells contain XXX while the remainder carry XX. The extent to which an individual is affected by the condition will depend upon the proportion of XXX to XX throughout.

Triple X can results either during the division of a parent's reproductive cells or during division of cells during early development.

It occurs in about one in every 1,000 female births. It is estimated that 90% of those affected are not diagnosed as they either have no or only few symptoms.