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Klinefelter syndrome

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

 

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

Causes

 

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.

 

Symptoms

 

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

 

Exams and Tests

 

Klinefelter syndrome may first be diagnosed when a man comes to the health care provider because of infertility. The following tests may be performed:

  • Karyotyping (checks the chromosomes)
  • Semen count

Blood tests will be done to check hormone levels including:

  • Estradiol, a type of estrogen
  • Follicle stimulating hormone
  • Luteinizing hormone
  • Testosterone

 

Treatment

 

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. But, an infertility specialist may be able to help. Seeing a doctor called an endocrinologist may also be helpful.

 

Support Groups

 

These groups can provide more information:

The American Association for Klinefelter Syndrome Information and Support (AAKSIS) -- www.aaksis.org

National Institute of Health, National Human Genome Research Institute -- www.genome.gov/19519068

 

Possible Complications

 

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 Sjogren 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 to Contact a Medical Professional

 

Call for an appointment with 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.

 

 

References

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, Bremmer WJ. Testicular disorders. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 19.

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

 

        A Closer Look

         

          Talking to your MD

           

            Self Care

             

              Tests for Klinefelter syndrome

               

                 

                Review Date: 10/30/2016

                Reviewed By: Anna C. Edens Hurst, MD, MS, Assistant 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, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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