U.S. National Library of MedicineNational Institutes of Health
Skip navigation
MedlinePlus Trusted Health Information for You MedlinePlus Trusted Health Information for You MedlinePlus Trusted Health Information for You
  FAQs Site Map About MedelinePlus Contact Us
español

Printer-friendly version E-mail this page to a friend
Illustration of chromosomes and DNA
  • Related Topics

  • Go Local

    • Services and providers for Klinefelter's Syndrome in the U.S.
  • National Institutes of Health

Also called: XXY male

Klinefelter's syndrome is a condition that occurs in men who have an extra X chromosome in most of their cells. The syndrome can affect different stages of physical, language and social development. The most common symptom is infertility. Because they often don't make as much of the male hormone testosterone as other boys, teenagers with Klinefelter's syndrome may have less facial and body hair and may be less muscular than other boys. They may have trouble using language to express themselves. They may be shy and have trouble fitting in.

It is important to start treatment as early as possible. With treatment, most boys grow up to have normal sex lives, successful careers and normal social relationships. Treatments include

  • Educational services
  • Physical, speech and occupational therapy
  • Medical treatments including testosterone replacement

National Institute of Child Health and Human Development

Start Here