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Triple X Syndrome (47,XXX-Syndrome) [Q97.0]

Dipl.-Biol. Uwe Heinrich

Scientific Background

Triple X syndrome is marked by trisomy of the X chromosome. Apart from an above-average body size, the female patients usually do not show any significant physical signs. Clinical consequences vary strongly; therefore, many women with triple X are never diagnosed with this chromosome aberration. Approx. 70% of all women are fertile; some, however, have irregular periods and premature ovarian failure (POF). Intelligence may be 10 to 15 points below the average of the family. Delay of speech development may occur. Offspring of triple X women are not at an elevated risk for gonosomal aneuploidy.

Frequency of the triple X syndrome in female newborns is 1:1,000. In 98% of all patients, the trisomy X is present in all cells, with 2% exhibiting the mosaic form.