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Two recent studies of Klinefelter syndrome (47XXY) are of interest to pediatricians.
The first study examined the changing prevalence of the syndrome. In population studies from the 1960s and 1970s, the three sex chromosome trisomies (XYY, XXY, and XXX) had similar prevalence, about 1 per 1000 same-sex births. Recently, increased prevalence has been noted for Klinefelter syndrome only. Now, researchers have examined its prevalence in live births using data from 16 studies and report an increase per 1000 male births from 1.09 in 1967 to 1.72 in 1988. According to the authors, the higher prevalence suggests that the rate of nondisjunction occurring at the first paternal meiotic division has increased during the last 30 to 40 years. They suspec…