Chromosome XXY: What is it? Causes, Symptoms, Diagnosis and Treatment

Another name given for this condition is “Klinefelter syndrome.”

Everything from your height to your hair color can be traced back to your genes. They have the code for how your body looks and works. Genes are grouped together on chromosomes. One pair, called the sex chromosome, determines whether you are male or female.

Women generally have two X chromosomes (XX). Men have an X and a Y (XY). But in rare cases, a man is born with an extra X chromosome (XXY). This is Klinefelter syndrome. Also called trisomy XXY.

Men often don’t even know they have Klinefelter until they have trouble trying to have a child. There is no cure, but it can be treated. With proper care, most men with Klinefelter lead normal, healthy lives.

What causes it?

The extra X chromosome is obtained by chance, or the egg or sperm that came together had an extra X chromosome. Older mothers are slightly more likely to have a child with Klinefelter, but the increase in likelihood is very small. Can have:

  • An extra X chromosome in each cell, which is the most common.
  • An extra X chromosome only in some cells, called the Klinefelter mosaic, where there are not as many symptoms.
  • More than one extra X chromosome, which is very rare and more severe.


Symptoms vary with age, and not all are always present. Some men show symptoms early on, but others don’t realize they have Klinefelter until puberty or into adulthood. And many men never realize they have it.


They may have problems at birth, such as a hernia or testicles that have not fallen into the scrotum. You may see the following signs in babies with Klinefelter:

  • Quieter than normal.
  • Slower to learn to sit, crawl, and speak.
  • Weaker muscles.


Children may have low energy levels or any of the following:

  • A difficult time to make friends and talk about feelings.
  • Problems learning to read, write, and do math.
  • Shyness and low confidence.


During adolescence, puberty may come later, may not end at all, or may not occur at all. Other possible symptoms include:

  • More developed breasts than normal.
  • Less facial hair and body hair.
  • Less muscle tone and muscles grow slower than normal.
  • Longer arms and legs, wider hips, and a shorter torso than other children his age.
  • Smaller limb and testicles.
  • Being taller than normal compared to the rest of the family.


In addition to the symptoms that teens show, men may have:

  • Infertility (you cannot have children because they cannot make enough sperm).
  • Low sexual desire
  • Low levels of testosterone.
  • Problems getting or keeping an erection.

Can it lead to other conditions?

Many problems caused by Klinefelter are due to lower levels of testosterone. You may have a slightly higher chance of:

  • Autoimmune problems, such as lupus and rheumatoid arthritis , in which your immune system attacks healthy parts of your body.
  • Breast cancer and cancers that affect the blood, bone marrow, and lymph nodes.
  • Conditions with your hormonal glands, such as diabetes.
  • Heart disease and blood vessel problems.
  • Lung disease.
  • Mental health problems, such as anxiety and depression.
  • Weak bones (osteoporosis).

Diagnosis and tests

Your doctor will begin with a physical exam and questions about your symptoms and general health. They will likely examine your chest, penis, and testicles and do some simple tests, such as checking your reflexes.

Your doctor can then run two main tests:

  • Chromosome analysis: Also called a karyotype analysis, this is a blood test that looks at your chromosomes.
  • Hormonal tests: they check the levels of hormones in the blood or urine.


It is never too late to get treatment, but the sooner you start, the better.

A common treatment is testosterone replacement therapy. It begins at puberty and can stimulate typical body changes, such as facial hair and a deeper voice. It can also help with penis size and stronger muscles and bones, but will not affect the size or fertility of the testicles.

Testosterone replacement therapy throughout your life can help prevent some of the long-term problems that come with Klinefelter.

Other treatments may include:

  • Counseling and support for mental health problems.
  • Fertility treatment (in some cases, using your own sperm to father a child).
  • Occupational and physical therapy to help with coordination and build muscles.
  • Plastic surgery to reduce the size of the breasts.
  • Speech therapy for children.
  • Support at school to help with social skills and learning delays.

If your child has Klinefelter, you can suggest that:

  • Play sports and other physical activities to build muscle.
  • Participate in group activities to learn social skills.