Extra X-Chromosome Abnormalities (XXX and Klinefelter)

XXX, or Triple-X, refers to an abnormality that occurs in females where they have an extra X chromosome. This abnormality results in almost no negative features in the babies. The girls who have it are usually tall, and have normal intelligence and fertility. They may have some learning disabilities, but that is all.

The odds of this abnormality occurring are approximately 1 in 1,500. Parents or affected children will likely not even be aware of it unless testing is done.

The appearance of an extra (or even more) X chromosome in males is known as Klinefelter syndrome. Symptoms include learning disabilities, problems with impulse control, lower levels of testosterone than the average male, and infertility. This abnormality occurs in about 1 in 700 boys.

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