Klinfelter's syndrome
- Any combinations of sex chromosomes other than XX (female) and XY (male) are referred to as atypical
- These patterns can be inherited, or may occur at conception or be due to division of the human reproductive cells before conception
- All babies will have an X chromosome, as human life cannot exist without this, but XXY, XYY, and XO (where the additional X is missing) are all possible
Klinefelter’s Syndrome (KS)
- KS affects about 1 in every 600 males (Klinefelter’s Syndrome Association, 2023) and involves having an extra X (female) chromosome, giving the atypical sex chromosome pattern of XXY and an excess of oestrogen in the body
- KS is due to an error in the egg cell when it develops and before it is fertilised or if the father’s sperm carries an extra X chromosome
- KS may not be discovered until puberty, especially in the case of the much more common and milder ‘mosaic’ KS, where only some of the boy’s cells have the XXY chromosomal pattern and the others are normal
- KS is incurable, but treatment with additional testosterone can increase muscle and bone development, though it cannot not reverse infertility
The characteristics of Klinefelter’s Syndrome
Physical |
Cognitive |
Small testes, producing low levels of testosterone, and small penis |
Poor language skills that affect reading and writing abilities |
No facial hair and limited pubic and body hair |
Poor mathematical skills |
Broader hips, long legs and arms in relation to torso and development of breast tissue |
Quiet, shy temperament with attention difficulties |
Delayed or incomplete puberty (some boys do not go through puberty at all) and infertility is likely |
Increased risk of anxiety disorders and/or depression |
Klinefelter’s Syndrome karyotype.