A syndrome affecting males in which the cells have an extra X chromosome (in addition to the normal XY), characterized by a tall thin physique, small infertile testes, and enlarged breasts.‘Risk factors for breast cancer in men suggest a hormonal imbalance, and up to 20 percent of male breast cancer cases have been associated with Klinefelter's syndrome.’
- ‘For example, a screening check of Down's Syndrome might pick up the extra X chromosome that occurs in Chris's condition, Klinefelter's syndrome.’
- ‘Men born with a genetic disorder called Klinefelter's syndrome often develop gynecomastia, as do males with adrenal tumors and liver disease.’
- ‘It is associated with breast and testicular abnormalities, infertility and Klinefelter's syndrome, a genetic abnormality in which men have one or more extra X chromosomes.’
- ‘In Klinefelter's syndrome, for instance, the presence of several X chromosomes and one Y chromosome sometimes results in sexual ‘ambiguity’.’
1940s named after Harry F. Klinefelter (born 1912), American physician.