This syndrome affects males. The karyotype of Klinefelter’s syndrome is 47, XXY. It occurs in 1 per 1000 newborn males. If not detected earlier the affected individual and his family members may not even know about the condition. The body of a Klinefelter male may slightly appear like that of a female with wide hips, breasts, small testis and poor growth of the beard. Secondary sexual characteristics in Klinefelter individuals are underdeveloped accompanying mosaicism. These individuals exhibit the presence of a Barr body. They have to undergo a hormone treatment such as testosterone therapy. An egg or a sperm cell may gain an extra X chromosome due to non-disjunction. Mother’s age may be responsible for the non-disjunction. Pregnancy above 35 years of age imposes a great risk of developing this syndrome in the embryo. Mosaic Klinefelter syndrome arises due to an extra X chromosome in some cells and a normal XY complement in other cells. Klinefelter boys have very low energy, low self-esteem, shyness, and problems in reading and writing. In their later years of life, such individuals also experience erectile dysfunction and low sex drive.