Klinefelter syndrome
Overview
Klinefelter syndrome (sometimes called Klinefelter's, KS or XXY) is where boys and men are born with an extra X chromosome.
Symptoms
Klinefelter syndrome does not usually cause any obvious symptoms early in childhood, and even the later symptoms may be difficult to spot. Many boys and men do not realise they have it. Possible features, which are not always present, may include: in babies and toddlers – weak muscles and very flexible (hypermobile) joints, learning to sit up, crawl, walk and talk later than usual, being quieter and more passive than usual, having undescended testicles, only one testicle, or a smaller penisin childhood – shyness and low self-confidence, problems with reading, writing, spelling and paying attention, milddyslexiaordyspraxia, low energy levels, and difficulty socialising or expressing feelingsin teenagers – growing taller than expected for the family (with long arms and legs), broad hips, poor muscle tone and slower than usual muscle growth, reduced facial and body hair that starts growing later than usual, small, firm testes, and enlarged breasts (gynaecomastia)in adulthood –inability to have children naturally (infertility),low sex drive, small, firm testes, and erection problems.
Causes
Klinefelter syndrome is caused by an additional X chromosome. This chromosome carries extra copies of genes, which may interfere with the development of the testicles and mean they produce less testosterone (male sex hormone) than usual. The extra genetic information may either be carried in every cell in the body or it may only affect some cells (known as mosaic Klinefelter syndrome). Klinefelter syndrome is not directly inherited – the additional X chromosome occurs as a result of either the mother's egg or the father's sperm having the extra X chromosome (an equal chance of this happening in either), so after conception the chromosome pattern is XXY rather than XY. This change in the egg or sperm seems to happen randomly. If you have a son with the condition, the chances of this happening again are very small. The risk of a woman having a son with Klinefelter syndrome may be slightly higher if the mother or father are older.
Treatment
There's no cure for Klinefelter syndrome, but some of the problems associated with the condition can be treated if necessary. Possible treatments include: testosterone replacement therapyspeech and language therapy during childhood to help with speech developmenteducational and behavioural support at school to help with any learning difficulties or behaviour problemsoccupational therapyto help with any co-ordination problems associated with dyspraxiaphysiotherapyto help build muscle and increase strengthpsychological support for any mental health issuesfertility treatment– options includeartificial inseminationusing donor sperm or possiblyintracytoplasmic sperm injection (ICSI), where sperm removed during a small operation are used to fertilise an egg in a laboratorybreast reduction surgeryto remove excess breast tissue TRT involves taking medicines containing testosterone. It can be taken in the form of gels or tablets in children, or given as gel or injections in adult men. TRT may be considered once puberty begins and may help with the development of a deep voice, facial and body hair, an increase in muscle mass, reduction in body fat, and improvement in energy. There is also evidence that it can help with learning and behavioural problems. You should see a specialist in children's hormones (a paediatric endocrinologist) at this time. Long-term treatment during adulthood may also help with several other problems associated with Klinefelter syndrome – including osteoporosis, low mood, reduced sex drive, low self-esteem and low energy levels – although it cannot reverse infertility. TRT may be stopped during fertility treatment, or not started until after fertility treatment. Treatment with TRT will be monitored by your care team as it can cause side effects and health issues.