Helpline 0300 111 4748

KS/XXY for Families

Klinefelter’s Syndrome (KS)/XXY is a common congenital condition (that means it is present at birth).

It is found in around 1 in 600 live male births and is caused by the presence of one or more additional sex chromosomes. The extra chromosome(s) can come from either parent. It occurs by chance and isn’t because of something which you have – or haven’t done. 

If you have just received a diagnosis of Klinefelter’s Syndrome (KS)/XXY for your child or unborn baby you have come to the right place for reliable information and friendly support. The most important thing to remember is that KS/XXY has a very wide range of effects, the severity of which varies considerably from person to person. However we do know that early diagnosis and appropriate support can make a huge difference!, so your child is one of the lucky ones.

Many of our members are successful in their chosen fields of employment and in their personal relationships. Others found school difficult and some find it more difficult to maintain relationships. Some may need some level of support throughout their lives.

Although the condition is relatively common, its effects are not well understood. Many members of the medical profession still think it is very rare and may be dismissive. Remind them that KS/XXY affects 1 in 600.

Scientific background

Common symptoms


What next?

Common health issues

Fertility options

The future

Useful links

What is Klinefelter's Syndrome (KS/XXY)?

Klinefelter’s Syndrome (KS)/XXY is  a common congenital condition (this means it is present from birth). It occurs in around 1 in 600 live male births and is caused by the presence of one or more additional sex chromosomes. Chromosomes are genetic material. Males typically have one X and one Y chromosome (XY) and females have two X chromosomes (XX). KS/XXY is characterised by the presence of an additional chromosome (XXY).

KS/XXY is diagnosed by a genetic blood test which identifies any abnormalities in the karyotype i.e. the number, size and shape of the chromosomes.

It is not life threatening. It wasn’t caused by anything you did and it is not inherited.
It is thought that 50% of XXY foetuses are miscarried, so your child is a fighter!

Increasing prevalence of KS/XXY

In 2011, Dr. Pat Jacobs reported: ‘… a  startling rise of 60 per cent since the 1960s in babies with Klinefelter syndrome.’ The reason for this is not known but it may be linked to the general, and well-publicised, fall in sperm count and the rise of the number of abnormal sperm.

If you would like to talk to someone please call our Helpline:

0300 111 47 48.

Please remember that as the KSA is run entirely by volunteers. Sometimes there may not be anyone available to take your call. Please leave a message with your email address or phone number and we will get back to you.


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