Sections View Full Chapter Figures Tables Videos Full Chapter Figures Tables Videos Supplementary Content +++ Key Features ++ Males with 1 extra X chromosome (XXY) Tall stature, gynecomastia, atrophic testes, infertility +++ Clinical Findings ++ Boys are normal in appearance before puberty; after puberty, they have disproportionately long legs and arms, sparse body hair, a female escutcheon, gynecomastia, and small testes Infertility resulting from azoospermia; the seminiferous tubules are hyalinized Mental retardation is somewhat more common than in the general population, and many have learning problems Higher risk of osteoporosis, breast cancer, and diabetes mellitus +++ Diagnosis ++ Low serum testosterone Karyotype is typically 47, XXY but other sex chromosome anomalies cause variations of Klinefelter syndrome Screening for cancer (especially of the breast), deep venous thrombosis, and glucose intolerance is indicated +++ Treatment ++ Testosterone administration is advisable after puberty but will not restore fertility Intracytoplasmic sperm injection is possible using sperm obtained by testicular extraction GET ACCESS TO THIS RESOURCE Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth Get Free Access Through Your Institution Contact your institution's library to ask if they subscribe to McGraw-Hill Medical Products. Access My Subscription GET ACCESS TO THIS RESOURCE Subscription Options Pay Per View Timed Access to all of AccessMedicine 24 Hour $34.95 (USD) Buy Now 48 Hour $54.95 (USD) Buy Now Best Value AccessMedicine Full Site: One-Year Individual Subscription $995 USD Buy Now View All Subscription Options