Klinefelter Syndrome was first described in 1942 by American physician Harry Klinefelter and his colleagues. In 1959, British doctor Patricia A. Jacobs and her team discovered that while normal males have XY sex chromosomes, individuals with Klinefelter Syndrome possess an extra X chromosome (XXY). Due to this specific chromosomal abnormality, the syndrome became known as 47,XXY syndrome thereafter. Klinefelter Syndrome, the most common sex chromosome disorder associated with hypogonadism (low male hormone levels) and infertility in males, affects approximately 1 in 500 to 1000 males.