Klinefelter’s Syndrome (47,XXY)
Print Friendly, PDF & Email

almostadoctor app banner for android and iOS almostadoctor iPhone, iPad and android apps almostadoctor iOS app almostadoctor android app

This is the presence of an extra X chromosome in males to give (47,XXY). 


  • 1 in 1000 male live births

Clinical features

Usually diagnosed in childhood when there is:
  • Clumsyness
  • Learning difficulties (usually mild)
  • Typically intellectual ability is reduced y 10-20 IQ points, but still within the normal range. More susceptible to behavioural and psychological problems.
  • Self obsessed behaviour



  • Taller than average
  • Long limbs
  • Gynaecomastia + Infertility + small soft testes (Hypogonadism) (30% of cases)
  • ↑ Risk of
  • Most patients are infertile – there is a lack of sperm in the semen (azoospermia)


  • Testosterone – is often given from puberty onwards, and helps the development of secondary sexual characteristics. It also reduces the long-term risk of osteroporosis.However, puberty is often normal in most cases.


  • Extra X chromosome
  • Equal chance of inheritance from mother or father
    • Maternal cases often associated with advancing maternal age
  • Small proportion of cases are due to mosaicism
  • >2 X chromosomes are sometimes present. These cases are associated with more severe learning difficulties, and more pronounced features of Klinefelter’s.


Read more about our sources

Related Articles

Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

Leave a Reply