Klinefelter Syndrome

A common genetic condition in people assigned to males at birth (AMAB) who have an additional X chromosome is called Klinefelter Syndrome. The most common symptoms include breast growth, infertility, osteoporosis, and learning difficulties. Physicians usually prescribe physical and emotional therapy and hormone replacement therapy (HRT).

What is Klinefelter Syndrome?

In normal circumstances, AMAB has 46 chromosomes (46, XY) but those who suffer from Klinefelter syndrome have 47 chromosomes (47, XXY). This is a congenital disorder, which means you are born with it. Usually, symptoms are different among people. The diagnosis occurs early in life but in some cases, people may not know about this condition until adulthood when they notice infertility.

This condition is quite common and happens roughly in 1 from every 600 people AMAB. However, approximately 70%-80% do not know they have this disorder.


People usually experience two types of symptoms including physical and Neurological. The symptoms a person experiences fluctuate depending on the severity of the condition.

Physical Symptoms

This genetic disorder may affect the body and how it works. Examples include:

  • Smaller penis
  • Undescended testicles
  • Changed body proportions (such as long legs and a short trunk)
  • Radioulnar synostosis
  • Coordination problems
  • Testicular failure (not producing enough testosterone or sperm)
  • Gynecomastia (increased breasts) in teen or adult years
  • Elevated risk for blood clots
  • Increased risk of bone fractures

Those who experience this genetic condition experience infertility. If healthcare providers find sperm, they can collect and freeze it to help you have biological children later.

Neurological Symptoms

People who experience the following symptoms usually describe behavioral problems, learning issues, or mental conditions. Examples include:

  • Depression
  • Anxiety
  • Impulsive behavior
  • Social, emotional, or behavioral problems
  • Attention-deficit/hyperactivity disorder (ADHD)
  • Speech delays
  • Autism spectrum disorder

Contact a doctor immediately if you notice any of the symptoms listed above.


If a person is born with an additional X chromosome Klinefelter syndrome occurs. This can happen in several ways. For example:

  • An egg cell holds an extra X chromosome
  • A sperm cell carries an extra X chromosome
  • During early fetal development, cells may divide improperly. In such cases, physicians call this disorder mosaic Klinefelter syndrome.


Those who experience this genetic condition are more likely to develop metabolism syndromes. Check some examples below:

  • High blood pressure (hypertension)
  • High cholesterol levels
  • High triglycerides in the blood
  • Type 2 diabetes

Check below other complications that could occur in people with Klinefelter syndrome:

  • Breast cancer
  • Gynecomastia
  • Tremors
  • Osteoporosis (brittle bones)
  • Autoimmune conditions (such as type 1 diabetes, thyroid disease, lupus, rheumatoid arthritis, and others)
  • Seizure disorder


Healthcare professionals usually diagnose Klinefelter syndrome in the following cases. For example:

  • Fetal development – Commonly, doctors don’t do any tests for Klinefelter syndrome but diagnose it during genetic tests for other reasons. For example amniocentesis and chorionic villus sampling.
  • Childhood or adolescence – Physicians may test you for this genetic disorder if during physical examination they notice atypical growth or development.
  • Adulthood – Decreased testosterone levels or fertility problems are factors that could make your provider test you for Klinefelter syndrome.

Additionally, people with mild Klinefelter syndrome usually do not experience any symptoms and they do not know they have this disorder. The only way to diagnose this genetic condition in such people is a fertility test.


Unfortunately, there is no cure for this condition because you are born with it and it is a part of your genetic code. It means that you cannot get rid of it. However, with the proper treatment, you can lessen the symptoms and improve your quality of life. Check below some treatment options:

  • Hormone Replacement
  • Therapy
  • Treatments for other diseases
  • Surgery (very rare)

Hormone Replacement

Usually, those who experience Klinefelter syndrome have reduced levels of testosterone compared to those without this disorder. Furthermore, someone may not start puberty or start but stop or regress. Testosterone levels often decrease due to testicles “failing”. To lessen the symptoms, it is recommended hormone therapy. The replacement of testosterone is done with injections (for children and teens). However, for adults, there are other treatment options. For example:

  • Testosterone subcutaneous pellets
  • Testosterone patches
  • Testosterone gels

Check below some goals of hormone replacement therapy:

  • Stronger muscles
  • Improved mood and overall mental health
  • An increase in sex drive
  • Deeper voice
  • Increased body and facial hair
  • Stronger bones


This is usually a part of the treatment. For example:

  • Emotional, behavioral, and family therapists (psychological support)
  • Occupational therapists (motor skills and coordination)
  • Physical therapists (build muscle)
  • Speech-language Pathologists or SPLs (help with speech development)

Some changes in the classrooms or learning environments may be required for children with this genetic condition.


About 50% of teenagers AMAB usually develop extra breast tissue. In case you are concerned about increased breast tissue, your doctor may recommend gynecomastia surgery. However, most physicians recommend doing this procedure in adulthood.

Is it Possible to Prevent Klinefelter Syndrome?

No, you can prevent this condition because usually you are born with it. It means that it is a random change in your genetic code that occurs before birth. Fortunately, you cannot pass this genetic disorder to your children. Furthermore, even parents cannot do something to prevent Klinefelter syndrome in their child.

Frequently Asked Questions

What other tests can help to diagnose this genetic disorder?

The goal of all tests that are done for Klinefelter syndrome diagnosis is to identify an additional X chromosome. The most common method to diagnose this condition is a blood test (karyotype test) that shows the number of present chromosomes. This test can be used even in fetuses before birth.

How long can an individual live with this genetic disease?

In most cases, those who experience Klinefelter syndrome have a normal life expectancy. Thus, a suitable treatment helps an individual live a full, happy, and healthy life with this disorder. However, leaving untreated the Klinefelter syndrome may lead to some life-threatening complications. Discuss with your healthcare provider for more details.

When should I see my doctor?

It is advised to see the child’s pediatrician if you notice certain symptoms in your child. For example long legs, short torso, taller than average stature, low energy, behavioral issues, learning challenges, and others. The doctor will ask some questions about the symptoms to determine whether you have Klinefelter syndrome or other genetic disorder.

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