This is the presence of an extra X chromosome in males to give (47,XXY).
- 1 in 1000 male live births
Usually diagnosed in childhood when there is:
- 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.