Common symptoms

KS is a spectrum condition - the severity and frequency of symptoms varies considerably from child to child. The following symptoms may occur often ... but not always!

Your child is very lucky to have been diagnosed early in life as 75% are never diagnosed. 

Early diagnosis, appropriate support and a healthy lifestyle can make a huge difference!


Physical symptoms

KS/XXY babies are sometimes identified as 'floppy babies'.  Their muscle tone may be poor, causing excessive flexibility of the joints. This can delay physical development - sitting up, walking.  Can cause clumsiness. The internal muscles can also be affected causing difficulty sucking, swallowing and constipation.  Physiotherapy may help. Encourage your child to be active. This will help to strengthen muscles.

Undescended  testicle(s) are common. Usually doctors will recommend a small operation to avoid the risk of them becoming cancerous.

Some boys may have a smaller than average penis.

Most KS/XXY youngsters are tall compared to their families, but this does not mean that all are very tall! If family members are generally on the short side then the KS/XXY person may be of average height ie tall compared to the rest of the family.

Generally the legs and arms are long, but the trunk is shorter than is usual.

Hands can be on the small side.

Dyspraxia is a common disorder affecting coordination in children and adults.  

Handwriting and general dexterity is often affected.

Because the testes don’t function properly, they can make more oestrogen than that is usual for an XY  male. This may  give rise to an increase in breast tissue (gynaecomastia). This can sometimes be made worse by testosterone replacement therapy (TRT) as testosterone  can often also be transformed into oestrogen.

Although there is an increased  risk of breast cancer, it appears to be about  70% lower than for females. Mosaics may have a slightly higher risk than non-mosaics.

It is recommended that all KS/XXY adults should self-examine regularly.

Where there is excessive breast tissue which is causing distress, removal may be funded by the NHS. However, this will depend on individual consultants, the area of the country and the individual's overall health.

It is important that the decision to have surgery is the KS/XXY person's decision and not the decision of medics or other adults.

A plastic surgeon with previous experience  should be used rather than a general surgeon.

In some situations a small incision can be made just beneath the breast and the excess tissue removed by liposuction. This can be carried out as a day procedure. However this may not always be suitable.

If liposuction is not possible, then a small incision is made just below the nipple and the excess tissue is removed. This will  leave a small scar which should be unobtrusive.

This should be discussed with your surgeon so that you know what to expect.

Many people who have KS/XXY suffer from sudden, apparently random bouts of extreme tiredness. The causes of this are unexplained. However, many use a great deal of energy coping with their poor information processing skills and some also use up a great deal of nervous energy. This tiredness can cause problems in school.

Cognitive symptoms

Those affected by KS/XXY often have a difficulty learning, although IQ is usually within the normal range.

Language and speech development disorders are the most common symptom seen in children with KS/XXY. This is an invisible disability which is still  common in adults, although many  will have developed coping strategies.

As language is essential for social interaction, many struggle in social situations. There is often difficulty in understanding the nuances of social behaviour as well as the nuances of  language. Literal  interpretation of language can  cause difficulties.

There is often a difficulty with self-expression -  especially when under pressure.

Although most KS/XXY youngsters have an IQ in the normal range, the majority do have some level of  learning difficulty. These are often associated with difficulty processing information particularly if it is presented verbally.


It will help your child if you write things down. Keep instructions and sentences simple.

Visual aids are very effective as these children often have enhanced visual skills – use of colour is particularly useful.

Support at school can help your child to reach their potential.

Executive function (EF) encompasses the abilities needed to organise thought and activities, to make plans and carry them out: 

  • organisation of tasks
  • use of one's time,
  • setting goals and priorities
  • assessing progress

It includes working memory, self monitoring, initiation, emotional control and the ability to shift from task to task. 

Your child may need support in these areas  to improve these skills.

It has been recognised that particular areas of the brain may develop differently in a KS/XXY person and that could be why short term memory can be poor.

There is often difficulty in processing information - especially if given verbally. As short term memory can also be poor, by the time the second instruction has been understood, the first one may have been  forgotten.

Written  information and  instructions are helpful. Extra time should be allowed  for the processing of information. It is very important to give  time for reflection - excessive pressure will make a situation worse.

Possible brain differences may be the cause of problems with concentration. In addition, those with KS/XXY often have enhanced sensory perception which may affect concentration. Sometimes,  particularly acute hearing can make  general noise and bustle very distracting.  Others may be very aware of touch and find chafing clothing labels or texture are an added distraction.

It is important to realise that often they are working twice as hard as their peers just to overcome their concentration, memory  and  information/language processing difficulties.

Limiting distractions and breaking work down into manageable chunks can help.

Because of their poor expressive language skills they often have difficulty putting their thoughts, ideas and emotions into words. This can lead to considerable frustration. Always allow your child time to gather thoughts together – and to take in what has been said.  People with KS/XXY are likely to have a reflective approach to learning meaning they need extra time to process the information.

As language is essential for building and maintaining social relationships, the KS/XXY child may find it difficult to learn appropriate social behaviour. Many have autistic tendencies or may be on the autistic spectrum. They often find it difficult to interpret social cues such as facial expressions and they do not notice nuances or slight differences in behaviour. Literal interpretation of language can also cause difficulties. Professional intervention can help considerably.

Other common symptoms

KS/XXY youngsters are often shy and lacking in self esteem.  However, supportive family and friends can help.

Most do not enjoy team games possibly because they dislike the physicality but also because language and information processing problems may  cause difficulty in understanding rules. Poor coordination may be another drawback.

In addition, the use of communal changing rooms may be disliked as  physical differences are on view.

However many do well at individual sports such as swimming and cycling.

Many of these ‘symptoms’ may be experienced by youngsters who are not KS/XXY. 

As KS/XXY folk often learn strategies to compensate as they get older, many of these symptoms may not be as obvious in adults.