1. Fertilizing a double X egg with a normal sperm also produces an XXY offspring (Klinefelter).

2. Klinefelter worked at the Massachusetts General Hospital in Boston from 1941-1942; under the supervision of Fuller Albright he described a group of nine men with "gynecomastia, aspermatogenesis without aleydigism, and increased excretion of follicle-stimulating hormone", the first description of what would be called the Klinefelter syndrome.

3. Although only sporadically reported in adults, 1-5 testicular calcifications appear to be more common in children and tend to be associated with Cryptorchidisme-11 or Klinefelter syndrome