title: Klinefelter's syndrome in nontwin brothers and maternal XX/XXX mosaicism.
abstract: A case of two nontwin brothers, 19 and 17 years old, who had both Klinefelter's syndrome with a chromosomal mosaicism 46 XY/47 XXY, is reported here. The analysis of their mother's karyotype revealed a 46 XX/47 XXX mosaicism. It is hypothesized that the presence of an extra X chromosome in all three subjects could depend on the transmission of two X chromosomes from the mother to the sons or, less likely, on an increased liability to nondisjunction of the X chromosomes during one of the early mitotic divisions in the zygotes.
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007621:Karyotyping; D007713:Klinefelter Syndrome / Q000235:genetics*; D008297:Male; D009030:Mosaicism; D012729:Sex Chromosome Aberrations; D012730:Sex Chromosomes; D014960:X Chromosome