Common Questions about Klinefelter Syndrome

Klinefelter Syndrome

In 1942, Dr. Harry Klinefelter, an American endocrinologist working at Massachusetts General Hospital published a report analyzing nine men who were presenting a combination of unique features like enlarged breasts, lack of facial hair and smaller testes that are unable to produce sperms. He thought this was due to an endocrine (hormonal) imbalance of unknown mechanism as suggested in his report and didn't consider it to be genetic in origin. It was only fourteen years later a group of researchers found that these males have an extra ‘x' chromosome giving XXY chromosomal pattern contrary to normal XY pattern, which is responsible for their unique characteristics

How common is it?

Despite the popular belief, Klinefelter syndrome is a fairly common chromosomal disorder as roughly 1 in 1000 boys are born with it. Nevertheless, only 10 percent of babies are identified before birth and only 25 percent is detected during their adulthood making it a ‘commonly undiagnosed' genetic disorder.

How does it happen?

Males have XY sex chromosomal pattern which they have inherited from their parents. Y comes from father and X from the mother.However, the reason behind this unusual chromosomal pattern is called ‘nondisjunction' in which two homologous (lying together) chromosomes, XY in sperm and XX in egg fails to separate, giving the characteristic ‘XXY' pattern.


XY sperm (failed to separate) + X (single X from a normal egg) = XXY

Y (from a normal sperm, separated) + XX (failed to separate egg) =XXY

It is crucial to know that this is a random genetic failure that occurs without any known influence. This ‘bonus' X, being a sex chromosome, it commonly causes infertility in affected males.

Any risk factors?

This is a 100 percent random event and studies haven't found any contributing factors except maternal (mother's) advanced age, which may pose a slight risk. Maternal old age is also found to be associated with genetic complications like trisomy 21, trisomy18, and triple X syndrome.

Noticeable features in Klinefelter

This disorder often goes undiagnosed till adulthood as features are not evident in babies and children. Though less noticeable, a careful examination can make an early identification which is important for proper management. Presenting features vary according to the age.

  1. Newborns/toddlers

Klinefelter toddlers are uniquely quieter than others and they take more time to start speaking. The rate of muscle growth is reduced needing more time to achieve developmental milestones like crawling, sitting, walking etc.

  1. Children
  • Taller with long legs
  • Micropenis (small penis)
  • Smaller hard testes.
  • Enlarged breasts
  • Weak, pliable bones subject to injuries
  • Delay in puberty and compared secondary sexual features like less facial hair compared to peers.
  • Can be antisocial due to difficulty in expressing feelings.
  1. Adult men
  • Impaired sex drive
  • Infertile
  • Increased abdominal fat
  • Tall with long legs
  • Gynecomastia (enlarged breasts)
  • Poorly distributed body hair

So if you or your son shows inadequate childhood mental and physical development or some of above features plus infertility, you may want to consult your doctor as early diagnosis is key. A lab test can confirm this condition. Pregnant mothers can get their amniotic fluid tested though not done frequently. Most adults with Klinefelter are diagnosed for the first time when they seek treatments for infertility.

Can genetic diseases be cured?

There is no cure as the issue lies in our genes. Males with Klinefelter have significantly low serum testosterone which is the main contributing factor for the symptoms. So, by restoring serum levels of testosterone preferably around the age of puberty, boys will get a normal physical growth. However, this cannot cure infertility.

Behavioral therapy, including speech therapy, is essential to teach the boys how to mingle in the society, handle problems at school (peer pressure) and correct speech issues.

Will they be able to get a woman pregnant?

Under normal circumstances, no they cannot, as their sperm count is significantly less than normal individuals. Still, due to the advancement of reproductive medicine, viable sperms can be collected through aspiration from testicles and used for ‘In Vitro fertilization', where sperms are fertilized with an egg in the lab. However, the success rate is 45 to 57 percent.

Any complications?

Complications are common in undiagnosed cases. Usual issues include weak bones due to reduced testosterone, breast cancer, lung diseases and cardiovascular defects.

Can they live long?

Yes, they can live up to the same age as healthy men. However, a combination therapy comprising behavior therapy, counseling, family support, drug therapy and surgery may be needed for longevity.

Last Reviewed:
January 18, 2017
Last Updated:
October 20, 2017
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