This is Klinefelter syndrome with a 47, XXY karyotype. A non-dysjunctional event in meiosis (maternal or paternal) left two X chromosomes in an ovum or a sperm. This syndrome is relatively common (about 1 in 500 males). Affected males are usually normal, though they may be tall and have small testes. Infertility results from decreased sperm (oligospermia) or absent sperm (aspermia). About half have gynecomastia. About 10% of cases are mosaics and are less affected.

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