Case #15 Male infertility from Kleinfelter Syndrome of testicular dysgenesis (XXY).   Male infertility requires physical examination and semen analysis. Poor quality sperm can result from simple causes, such as tight pants and varicocele that interfere with normal testicular thermoregulation (cremasteric muscle). Drugs, testicular trauma, cryptorchidism (undescended “hidden” testes), hypogonadism, etc. Are other possible causes. Azoospermia (no sperm) results from obstruction of ducts (vas deferens) or primary testicular failure. Primary hypogonadism is caused by cryptorchidism, Leydig cell aplasia, seminiferous tubule failure (infection, radiation, uremia), myotonic dystrophy, Kartagener (immotile cilia) syndrome. Kleinfelter (XXY) occurs in 1/700 male births, and causes primary testicular dysgenesis. Chromatin (Barr) bodies are found on buccal smear.   Testicular hyperthermia: (tight pants, undescended testes, varicocele) Semen analysis, cytogenetics