Klinefelter's Syndrome Questions

Klinefelter's Syndrome Bibliography
Klinefelter's Syndrome
XXY Male
By: Mia C., Peyton H., Laticia L., and Ashley W.


What is it?

Klinefelter's Syndrome is a circumstance that occurs only in men who carry an extra X chromosome.


About the Syndrome:

Klinefelter’s Syndrome is disorder found in men with an extra X chromosome. This disorder affects the amount of testosterone produced in the body. As babies these XXY males are a lot weaker than the average baby. They may or may not, depending on the baby, sit up, crawl and walk later than the average baby. Later on once they enter the toddler stage these XXY males tend to be taller than usual and have less muscle and coordination control. As life carries on and puberty hits, XXY males don’t experience the same types of changes as average boys do.

They also lack self-confidence, tend to be a lot quieter, shy and struggle in school and sports. Then during adulthood things get better and the XXY males start to resemble males without the condition. However, these XXY males still lack production of testosterone; meaning it may be harder or impossible for the XXY males to have children.


Klinefelter Syndrome also increases the chances of: breast cancer, lung disease, vein diseases, osteoporosis, extragonadal germ cell tumor, tooth decay, enlarged breasts, abnormal body proportions, depression, dyslexia, learning disabilities, and attention deficient hyperactivity disorder (ADHD). XXY males may also have a harder time doing work that involves reading and writing.

Klinefelters Syndrome is not inherited. It most commonly happens as a random event while sex cells are forming. Nondisjunction occurs which leaves a reproductive cell with an abnormal amount of chromosomes. For example, an egg or sperm cell receive an extra (and sometimes even more than one extra) X chromosome(s) due to nondisjunction. If the chromosome that received more than one X is passed down to a child, then that child will have one (or more) extra X chromosomes in every cell of their body.

However, there is such a thing called Mosaic Klinefelters Syndrome where the extra X chromosme(s) are not present in every cell of the person. This means that the affected male will have a better likelihood of reproducing.


  • Infertility (not being able to get a women pregnant)

    Male with Klinefelter's Syndrome
  • Low testosterone levels (the male hormone)

  • Less facial and body hair

  • Less muscular than other boys

  • Sexual problems

  • Abnormally large breasts (Gynecomastia)

  • Abnormal body proportions

  • Speech Impediments (Hard time communicating with others)

  • Dyslexia


  • 1/500-1000 male births result in a baby with the syndrome.

  • 1/500-1000 are affected by the syndrome

  • Approximately 544,000 males in the USA have the syndrome.


  • Kleinfelter’s Syndrome was first reported in the year 1942 by Dr. Harry Klinefelter.

  • Kleinfelter’s syndrome is in fact a very common genetic disorder among men. Statistically, it affects between 1 in 500 and 1 in 1,000 males.

  • A percentage of men with this disorder actually do not notice they have it unless they get their blood tested, hit puberty or try to have children.

  • This disorder can be treated effectively with Hormone Replacement therapy.

  • Along with treatment, many men can still live happy and normal lives with not many complications academically, sexually or socially.

  • Some men not only inherit an extra X chromosome, but in very rare cases, inherit three or four. When this occurs, the symptoms of this disorder are more exaggerated.

  • gynecomastia2.jpg
    Example of Gynecomastia
    Typical male Vs. Male with Klinefelter's

Benefits of Treatments:

  • Testosterone Therapy- has the most impact during the first years of a patient's life. When the syndrome is diagnosed during adulthood, testosterone therapy is not proven to be as successful.

    • Can help improve the following:

      • growth of body hairkleinfelter_karyotype.jpg

      • impove appearance of muscles

      • improve concentration

      • improve mood and self esteem

      • increase energy and sex drive

      • increase strength

  • Educational, Physical, Speech, Occupational Therapy
    • Can help boys have normal:

      • sex lives

      • successful careers

      • social relationships