About Klinefelter Syndrome
Klinefelter syndrome (47,XXY) is the most common sex chromosome disorder in males, characterised by an extra X chromosome. It affects testosterone production, fertility, and development. Most individuals are not diagnosed until puberty or adulthood when fertility issues or testosterone deficiency become apparent. Testosterone replacement therapy (TRT) is the cornerstone of treatment. Clinical trials are investigating fertility preservation, early testosterone intervention, and bone density outcomes. The syndrome is substantially underdiagnosed — estimated 75% of affected males are never diagnosed.
Common Clinical Features
Clinical Trial Eligibility Tips
What to know before applying to Klinefelter Syndrome trials.
Klinefelter syndrome is diagnosed by karyotype (chromosomal analysis) — a standard blood test can confirm 47,XXY.
Micro-TESE (testicular sperm extraction) is available to some Klinefelter males with azoospermia and is offered through specialised fertility centres — clinical trials are assessing fertility preservation timing.
The American Association for Klinefelter Syndrome Information and Support (AAKSIS) connects individuals to research programmes and peer networks.
Patient Resources
Find recruiting Klinefelter Syndrome trials
Search 500,000+ studies from ClinicalTrials.gov, filtered for Klinefelter Syndrome. Updated daily.