Klinefelter syndrome (KS) is a condition that occurs in men who have an extra X chromosome. The syndrome can affect different stages of physical, language, and social development.
The most common symptom is infertility. Boys may be taller than other boys their age, with more fat around the belly. After puberty, KS boys may have
- Smaller testes and penis
- Breast growth
- Less facial and body hair
- Reduced muscle tone
- Narrower shoulders and wider hips
- Weaker bones
- Decreased sexual interest
- Lower energy
KS males may have learning or language problems. They may be quiet and shy and have trouble fitting in.
A genetic test can diagnose KS. There is no cure, but treatments are available. It is important to start treatment as early as possible. With treatment, most boys grow up to have normal lives.
Treatments include testosterone replacement therapy and breast reduction surgery. If needed, physical, speech, language, and occupational therapy may also help.
NIH: National Institute of Child Health and Human Development
- How Do Health Care Providers Diagnose Klinefelter Syndrome? (National Institute of Child Health and Human Development)
- What Are Common Symptoms of Klinefelter Syndrome? (National Institute of Child Health and Human Development)
Treatments and Therapies
- What Are the Treatments for Symptoms in Klinefelter Syndrome? (National Institute of Child Health and Human Development)
- Klinefelter Syndrome (KS): Other FAQs (National Institute of Child Health and Human Development)
- Genetics Home Reference: Klinefelter syndrome (National Library of Medicine)
Statistics and Research
- How Many People Are Affected by or at Risk for Klinefelter Syndrome (KS)? (National Institute of Child Health and Human Development)
- ClinicalTrials.gov: Klinefelter Syndrome (National Institutes of Health)
Journal ArticlesReferences and abstracts from MEDLINE/PubMed (National Library of Medicine)
- Article: Sinus node dysfunction requiring permanent pacemaker implantation in a young...
- Article: Re: successful testicular sperm retrieval in adolescents with Klinefelter syndrome...
- Article: Global transcriptome analysis of peripheral blood identifies the most significantly...
- Klinefelter's Syndrome -- see more articles
Find an Expert
- Klinefelter Syndrome (Nemours Foundation)