Klinefelter’s Syndrome (47,XXY)

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

Epidemiology

• 1 in 1000 male live births

Clinical features

• 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

Adults

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

Treatment

• 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.

Cytoge​netics

• 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.

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