47 X-X-Y syndrome
Definition of Klinefelter syndrome
Klinefelter syndrome is the presence of an extra X chromosome in a male.
Causes, incidence, and risk factors
Humans have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. The two sex chromosomes determine if you become a boy or a girl. Females normally have two XX chromosomes. Males normally have an X and a Y chromosome.
Signs and tests
Klinefelter syndrome may first be diagnosed when a man comes to the doctor because of infertility. Infertity is the most common symptom.
Testosterone therapy may be prescribed. This can help:
Chad Haldeman-Englert, MD, Wake Forest University School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 11/1/2010