What is Klinefelter syndrome?

Klinefelter syndrome is a set of symptoms named after Dr. Harry Fitch Klinefelter, Jr. who was an American rheumatologist and endocrinologist.

Klinefelter syndrome (KS), also known as 47,XXY or XXY, is the set of symptoms that result from two or more X chromosomes in males. Often, symptoms may be subtle and many people do not realize they are affected until puberty when the boy's testicles fail to grow and there are other symptoms.

Klinefelter syndrome is a genetic condition. and occurs when a boy is born with one or more extra X chromosomes. 47, XXY for example.

The primary features of Klinefelter syndrome are:

  • male infertility
  • small testicles.

In addition, individuals with Klinefelter syndrome can have the following symptoms:

  • greater height
  • weaker muscles,,
  • poor coordination,
  • less body hair,
  • breast growth, and
  • less interest in sex.

Intelligence is usually normal; however, reading difficulties and problems with speech are more common

To find out if a boy or man has Klinefelter syndrome, the doctor will ask questions about his past health, do a physical exam, and order a chromosome test called a karyotype. The karyotype is a test of chromosomes and shows a pattern of 47 (usually there are 46) chromosomes with an addition X chromosomes for three "sex" chromosomes, XXY.

Orinial publication of Klinefelter syndrome:

Klinefelter, H.F., Jr.; Reifenstein, E.C., Jr.; Albright, F. (1942). "Syndrome characterized by gynaecomastia, aspermatogenesis without a-Leydigism, and increased excretion of follicle stimulating hormone". Journal of Clinical Endocrinology & Metabolism. 2 (11): 615–627.