Triple-X syndrome is characterized by a trisomy of the X chromosome. Patients usually do not show significant physical symptoms apart from an increased height. As the clinical impact is highly variable, many women with triple-X are never diagnosed with this chromosomal aberration. About 70% of women are fertile, but some present with menstrual irregularities and premature menopause. Intelligence may be 10-15 points below the family average. There may be a delay in speech development. Offspring of Triple-X women are not found to be at higher risk for gonosomal aneuploidy.
The prevalence of Triple-X syndrome is reported to be approximately 1:1,000 in female newborns. In 98% of patients, trisomy X is found in all cells, while 2% show mosaicism.
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