Klinefelter Syndrome

Klinefelter syndrome occurs when a male has an additional X chromosome, making them 47 XXY. Under normal circumstances males have XY sex chromosomes and females have XX sex chromosomes.

Rarely people with Klinefelter syndrome can have even more X chromosomes, such as 48 XXXY or 49 XXXXY. This is associated with more severe features.



Usually patients with Kleinfelter syndrome appear as normal males until puberty. At puberty can develop features suggestive of the condition:

  • Taller height
  • Wider hips
  • Gynaecomastia
  • Weaker muscles
  • Small testicles
  • Reduced libido
  • Shyness
  • Infertility
  • Subtle learning difficulties (particularly affecting speech and language)


Management Options

There is no way to treat the underlying genetic cause of Klinefelter syndrome. Treatment aims to help with the features of the condition:

  • Testosterone injections improve many of the symptoms
  • Advanced IVF techniques have the potential to allow fertility
  • Breast reduction surgery for cosmetic purposes

Multidisciplinary team input:

  • Speech and language therapy to improve speech and language
  • Occupational therapy to assist in day to day tasks
  • Physiotherapy to strengthen muscles and joints
  • Educational support where required for dyslexia and other learning difficulties



Life expectancy is close to normal. Infertility can occasionally be treated with advanced IVF techniques.

There is a slight increased risk of:

  • Breast cancer compared with other males (but still less than females)
  • Osteoporosis
  • Diabetes
  • Anxiety and depression


Last updated January 2020
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