Learn About Klinefelter Syndrome

What is the definition of Klinefelter Syndrome?

Klinefelter syndrome is a genetic condition that occurs in males when they have an extra X chromosome.

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What are the alternative names for Klinefelter Syndrome?

47 X-X-Y syndrome; XXY syndrome; XXY trisomy; 47,XXY/46,XY; Mosaic syndrome; Poly-X Klinefelter syndrome

What are the causes of Klinefelter Syndrome?

Most people have 46 chromosomes. Chromosomes contain all of your genes and DNA, the building blocks of the body. The 2 sex chromosomes (X and Y) determine if you become a boy or a girl. Girls normally have 2 X chromosomes. Boys normally have 1 X and 1 Y chromosome.

Klinefelter syndrome results when a boy is born with at least 1 extra X chromosome. This is written as XXY.

Klinefelter syndrome occurs in about 1 out of 500 to 1,000 baby boys. Women who get pregnant after age 35 are slightly more likely to have a boy with this syndrome than younger women.

What are the symptoms of Klinefelter Syndrome?

Infertility is the most common symptom of Klinefelter syndrome.

Symptoms may include any of the following:

  • Abnormal body proportions (long legs, short trunk, shoulder equal to hip size)
  • Abnormally large breasts (gynecomastia)
  • Infertility
  • Sexual problems
  • Less than normal amount of pubic, armpit, and facial hair
  • Small, firm testicles
  • Tall height
  • Small penis size
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What are the current treatments for Klinefelter Syndrome?

Testosterone therapy may be prescribed. This can help:

  • Grow body hair
  • Improve appearance of muscles
  • Improve concentration
  • Improve mood and self esteem
  • Increase energy and sex drive
  • Increase strength

Most men with this syndrome are not able to get a woman pregnant. An infertility specialist may be able to help. Seeing a doctor called an endocrinologist may also be helpful.

Who are the top Klinefelter Syndrome Local Doctors?
Highly rated in

University Of Brescia

Now With Department Of Medicine, Unit Of Andrology And Reproductive Medicine 
Padova, IT 

Alberto Ferlin is in Padova, Italy. Ferlin is rated as an Elite expert by MediFind in the treatment of Klinefelter Syndrome. He is also highly rated in 14 other conditions, according to our data. His top areas of expertise are Klinefelter Syndrome, Hypogonadism, Intersex, and Low Testosterone.

Highly rated in

Aarhus University Hospital

Aarhus University Hospital 
Aarhus N, DK 

Claus Gravholt is in Aarhus N, Denmark. Gravholt is rated as an Elite expert by MediFind in the treatment of Klinefelter Syndrome. He is also highly rated in 16 other conditions, according to our data. His top areas of expertise are Gonadal Dysgenesis, Intersex, Klinefelter Syndrome, and Hypogonadism.

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Highly rated in

Aarhus University Hospital

Arhus, DK 8200

Anne Skakkebaek is in Arhus, Denmark. Skakkebaek is rated as an Elite expert by MediFind in the treatment of Klinefelter Syndrome. She is also highly rated in 6 other conditions, according to our data. Her top areas of expertise are Klinefelter Syndrome, Intersex, Hypogonadism, and Triple X Syndrome.

What are the support groups for Klinefelter Syndrome?

These sources can provide more information on Klinefelter syndrome:

  • Association for X and Y Chromosome Variations -- genetic.org
  • US National Library of Medicine, MedlinePlus -- medlineplus.gov/klinefelterssyndrome.html
What are the possible complications of Klinefelter Syndrome?

Enlarged teeth with a thinning surface is very common in Klinefelter syndrome. This is called taurodontism. This can be seen on dental x-rays.

Klinefelter syndrome also increases the risk of:

  • Attention deficient hyperactivity disorder (ADHD)
  • Autoimmune disorders, such as lupus, rheumatoid arthritis, and Sjögren syndrome
  • Breast cancer in men
  • Depression
  • Learning disabilities, including dyslexia, which affects reading
  • A rare type of tumor called an extragonadal germ cell tumor
  • Lung disease
  • Osteoporosis
  • Varicose veins
When should I contact a medical professional for Klinefelter Syndrome?

Contact your provider if your son does not develop secondary sexual characteristics at puberty. This includes facial hair growth and a deepening of the voice.

A genetics counselor can provide information about this condition and direct you to support groups in your area.

What are the latest Klinefelter Syndrome Clinical Trials?
GROWing Up With Rare GENEtic Syndromes ….When Children With Complex Genetic Syndromes Reach Adult Age
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Turner And Klinefelter Treatment Target Study. Improving Endocrine Treatment by Linking Biochemical Parameters to Morbidity and Quality of Life in Patients With Turner and Klinefelter Syndrome
What are the Latest Advances for Klinefelter Syndrome?
Klinefelter syndrome presenting with perinatal ascites associated with unilateral renal agenesis and a prostatic utricle cyst.
Klinefelter syndrome: Advances in research.
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Glucose metabolic disorder in Klinefelter syndrome: a retrospective analysis in a single Chinese hospital and literature review.
Who are the sources who wrote this article ?

Published Date : October 27, 2020
Published By : Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

What are the references for this article ?

Allan CA, McLachlan RI. Androgen deficiency disorders. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 139.

Matsumoto AM, Anawalt BD, Testicular disorders. In: Melmed S, Auchus, RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 19.

Nussbaum RL, McInnes RR, Willard HF. The chromosomal and genomic basis of disease: disorders of the autosomes and sex chromosomes. In: Nussbaum RL, McInnes RR, Willard HF, eds. Thompson & Thompson Genetics in Medicine. 8th ed. Philadelphia, PA: Elsevier; 2016:chap 6.