Klinefelter Syndrome


Other Known Aliases47XXY, Klinefelter-Reifenstein-Albright Syndrome


DefinitionGenetic condition resulting from two (or more) X chromosomes in a male patient.  It is the most common sex chromosome abnormality causing hypogonadism.

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Clinical SignificanceThis condition affects 1 in 500-1000 newborn males in the United States.  Symptoms can range from subtle (sometimes not even noticed) to severe learning, developmental, and cognitive deficiencies.  The most prominent features are sterility, small testes, taller stature, less androgenic body hair, and gynecomastia.  Due to these developmental abnormalities, it is often not diagnosed until after puberty

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History – Named after Harry Fitch Klinefelter, Jr. (1912-1990), an American rheumatologist and endocrinologist, who earned is medical doctorate from Johns Hopkins University.  He worked in the prestigious clinic of Dr. Fuller Albright at Massachusetts General Hospital where he studied a group of nine boys who all had similar features of gynecomastia, aspermatogenesis, and increased follicle-stimulating hormone.  He credits Dr. Albright with this discovery, as it was his clinic and he first noticed the pattern, but Albright wanted Klinefelter to do the research work on it as a new fellow attending.  The group (with Dr. Edward Reifenstein) published this cases series in 1942 and Dr. Albright insisted that Klinefelter take lead authorship.


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  1. Firkin BG and Whitwirth JA.  Dictionary of Medical Eponyms. 2nd ed.  New York, NY; Parthenon Publishing Group. 1996.
  2. Bartolucci S, Forbis P.  Stedman’s Medical Eponyms.  2nd ed.  Baltimore, MD; LWW.  2005.
  3. Yee AJ, Pfiffner P. (2012).  Medical Eponyms (Version 1.4.2) [Mobile Application Software].  Retrieved http://itunes.apple.com.
  4. Whonamedit – dictionary of medical eponyms. http://www.whonamedit.com
  5. Up To Date. www.uptodate.com
  6. Klinefelter Syndrome.  https://ghr.nlm.nih.gov/condition/klinefelter-syndrome
  7. Klinefelter HF, Reifenstein EC, Albright F. Syndrome Characterized by Gynecomastia, Aspermatogenesis without A-Leydigism, and Increased Excretion of Follicle-Stimulating Hormone.  JCEM.  1942;2(11):615-627 [article]
  8. Loriau DL.  Chapter 89: Harry F. Klinefelter (1912-1990).  A Biographical History of Endocrinology. 2016.  [article]

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