Klinefelter syndrome (sometimes called Klinefelter’s, KS or XXY) is where boys and men are born with an extra X chromosome. The exact cause is not known but Klinefelter Syndrome is not inherited / hereditary.

Some of the main signs and symptoms include small and firm testes, reduced testosterone production, subfertility, and issues with intellectual and physical development. These symptoms are not present in all patients and can vary in severity. Klinefelter syndrome is diagnosed via blood tests that analyse chromosomes and test hormone function. There is no cure for Klinefelter syndrome but there are many treatments available for the problems associated with the condition. The Klinefelter Syndrome Multi-Specialty clinics are one of the first in the country to address the needs of patients diagnosed with Klinefelter (XXY) Syndrome.

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Klinefelter syndrome london andrology

As a result of abnormalities related to the sex chromosomes, KS is a condition that occurs in roughly one out of every 600 newborn boys.

Symptoms of KS disorder range from distorted body proportions, abnormally large breasts to small testicles and sexual problems.

The most common and potentially damaging problems is male infertility. In fact, sometimes men aren’t diagnosed with the condition until later adulthood, and are therefore more often diagnosed while seeking treatment for fertility concerns.


The combination of small firm testes and low sperm count (or absence of sperm in semen) indicates KS. The main investigations are blood tests that will analyse chromosomes and look at hormone function. Investigations should be carried out to check for other causes of small firm testes and low sperm count. Currently, there is no screening program for KS, although it may be picked up prenatally (before birth) as part of screening for other chromosome abnormalities.


These can be very mild and so it is estimated only 1 in 4 (25%) of children or adults with Klinefelter Syndrome are ever diagnosed. KS has a varying presentation and many boys and men do not realise they have it.

Patients with KS can have an increased risk of developing other health problems including:

  • Type 2 diabetes
  • Osteoporosis (fragile bones)
  • Blood clots
  • Autoimmune (when your immune system mistakenly “attacks” your body) disorders such as rheumatoid arthritis and systemic lupus erythematosus

Life expectancy is usually normal, and many patients live normal lives. In addition to the problems mentioned above, low testosterone can give a series of symptoms: low energy levels, increased daytime sleepiness, low libido (sex drive), and difficulty concentrating, which can be treated with testosterone supplementation.


There is a range of treatments available for KS including Testosterone Replacement Therapy, Fertility treatments, Endocrine (hormone) Management, and many more.

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