Klinefelter Syndrome

Klinefelter syndrome is a common genetic condition in which a male is born with an extra X chromosome.

Last Updated: February 21, 2024

About 1 in 600 males have Klinefelter syndrome, but around 70-80% of those with the syndrome do not know that they have it.

People have 46 chromosomes, two of which are sex chromosomes that tell what gender a person is. There are two X chromosomes in a woman (XX) while males have an X and Y chromosomes (XY). In Klinefelter syndrome, a man can have any of the following: 

  • The most common cause is an extra copy of the X chromosome in each cell (XXY)
  • Some of the cells have an extra X chromosome (also called as mosaic Klinefelter syndrome)
  • More than one extra copy of the X chromosome (XXXY)
  • Extra copies of genes on the X chromosome

Symptoms of Klinefelter syndrome present differently according to the level of development of the person.

In babies and toddlers, the disease can present as delayed learning which can be observed as sitting up, crawling, walking, and talking later than usual, as well as being quieter and less active.

In childhood, symptoms include shyness and low self-esteem, trouble reading, writing, spelling, and paying attention. Mild dyslexia or dyspraxia, low energy, and trouble making friends or expressing feelings can also be observed.

In adolescents, the usual signs are abnormal physical development in terms of height (with long arms and legs), hip width, muscle tone, rate of growth, hair growth (especially on the face and body) and sexual characteristics (such as tiny penises and testicles, or enlarged breast).

Apart from the aforementioned physical traits, adult acromegaly is characterized by an inability to conceive children (infertility) and a lack of sex drive.

Klinefelter syndrome is usually diagnosed through prenatal screening. Doctors can order a blood test for karyotyping wherein they look at the patient’s chromosomes to see whether the extra X chromosome is present. This can be done on kids, adults, and even babies before they are born.


Klinefelter syndrome cannot be treated, but some of the challenges that come with it can be managed if needed. Some supportive treatment include:

  • Testosterone replacement therapy
  • Speech and language therapy during childhood development
  • Support with learning and behavior at school to help with any learning problems or behavior issues
  • Occupational therapy to deal with problems with dyspraxia
  • Physiotherapy to help build muscle and get stronger
  • Fertility treatment options include artificial insemination with donor sperm or intracytoplasmic sperm injection (ICSI)
  • Surgery to remove extra breast tissue

Klinefelter syndrome, a hereditary disorder with no known cure, is unfortunately irreversible. It is a random mistake in the DNA that happens before birth. This is not an inherited disease, and there is nothing a parent can do to keep their child from getting Klinefelter syndrome.


National Health Services (2022). Klinefelter syndrome. Retrieved December 9, 2022, from https://www.nhs.uk/conditions/klinefelters-syndrome/#:~:text=Klinefelter%20syndrome%20(sometimes%20called%20Klinefelter's,genetic%20sex%20of%20a%20baby.

Mayo Clinic (2022). Klinefelter syndrome. Retrieved December 9, 2022, from https://www.mayoclinic.org/diseases-conditions/klinefelter-syndrome/symptoms-causes/syc-20353949

Cleveland Clinic (2022). Klinefelter syndrome. Retrieved December 9, 2022, from https://my.clevelandclinic.org/health/diseases/21116-klinefelter-syndrome

Last Updated: February 21, 2024