They are men with one or more extra X chromosomes. Men. Some men who suffer from this syndrome can be treated so as to be able to impregnate women with their ow

They are men with one or more extra X chromosomes. Men. Some men who suffer from this syndrome can be treated so as to be able to impregnate women with their own sperm. I assume that this only works for men who have partial/mosaic Klinefelter, otherwise their sperm could also contain double-X chromosomes - but maybe it also works for them, leading to an increase in children being born with this condition?