PURPOSE OF REVIEW: Klinefelter syndrome, 47,XXY and its variants, is the most common chromosomal aberration among men, with estimated frequency of 1: 500 among newborns. Men with Klinefelter syndrome present with sequels of hormonal and spermatogenic testicular failure like infertility, low testosterone, erectile dysfunction, and low bone mineral density. This review is aimed to provide the practicing urologist with an important source of clinically relevant information about Klinefelter syndrome. RECENT FINDINGS: Sperm can be found in over 50% of men with Klinefelter syndrome, thus men with Klinefelter syndrome are not sterile. Recent evidence suggests that children with Klinefelter syndrome are born with spermatogonia and lose large numbers of germ cells during puberty. Early diagnosis and treatment can improve the quality of life and the overall health of men with Klinefelter syndrome. SUMMARY: Growing interest in Klinefelter syndrome among translational scientists and clinicians will result in better understanding of the pathophysiology of testicular failure. In some states, screening programs for Klinefelter syndrome are already in place, which will increase the number of patients with Klinefelter syndrome seen by practicing urologists in the near future. Diagnosis and management of patients with Klinefelter syndrome is within the scope and training of urologists. Development of randomized clinical trials comparing different forms of interventions in men and children with Klinefelter syndrome will allow us to standardize the care of these patients.
