Klinefelter Syndrome

Summary

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

Learn More

• How Do Health Care Providers Diagnose Klinefelter Syndrome (KS)? (Eunice Kennedy Shriver National Institute of Child Health and Human Development) Also in Spanish
• Karyotyping (Medical Encyclopedia) Also in Spanish
• Klinefelter Syndrome (Mayo Foundation for Medical Education and Research)
• Klinefelter Syndrome (For Teens) (Nemours Foundation)
• Klinefelter Syndrome (KS): Condition Information (Eunice Kennedy Shriver National Institute of Child Health and Human Development) Also in Spanish
• Klinefelter Syndrome (KS): Other FAQs (Eunice Kennedy Shriver National Institute of Child Health and Human Development) Also in Spanish
• Learning about Klinefelter Syndrome (National Human Genome Research Institute)
• What Are Common Symptoms of Klinefelter Syndrome (KS)? (Eunice Kennedy Shriver National Institute of Child Health and Human Development) Also in Spanish
• What Are the Treatments for Symptoms in Klinefelter Syndrome (KS)? (Eunice Kennedy Shriver National Institute of Child Health and Human Development) Also in Spanish

Genetics

• 48,XXXY syndrome: MedlinePlus Genetics (National Library of Medicine)
• 49,XXXXY syndrome: MedlinePlus Genetics (National Library of Medicine)
• Klinefelter syndrome: MedlinePlus Genetics (National Library of Medicine)

Clinical Trials

• ClinicalTrials.gov: Klinefelter Syndrome (National Institutes of Health)

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

• Article: Cardiorespiratory fitness in adolescents and young adults with Klinefelter syndrome -...
• Article: A dual-center study of predictive factors for sperm retrieval through microdissection...
• Article: Transcriptomic differences between fibrotic and non-fibrotic testicular tissue reveal possible key...
• Klinefelter Syndrome -- see more articles

Patient Handouts

• Klinefelter syndrome (Medical Encyclopedia) Also in Spanish