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Down syndrome

Definition:

Down syndrome is a genetic condition in which a person has 47 chromosomes instead of the usual 46.

Alternative Names:

Trisomy 21

Causes, incidence, and risk factors:

In most cases, Down syndrome occurs when there is an extra copy of chromosome 21. This form of Down syndrome is called Trisomy 21. The extra chromosome causes problems with the way the body and brain develop.

Down syndrome is the most common single cause of human birth defects.

References:

Ferri FF. Ferri’s Clinical Advisor 2007: Instant Diagnosis and Treatment. 9th ed. St. Louis, Mo: Mosby; 2007.

ACOG Committee on Practice Bulletins. ACOG Practice Bulletin No. 77: screening for fetal chromosomal abnormalities. Obstet Gynecol . 2007 Jan;109(1):217-27.

AAP Committee on Genetics. Health supervision for children with Down syndrome. Pediatrics . 2001 Feb;107(2):442-9.

Review Date: 5/10/2007
Reviewed By: Rachel A Lewis, MD, FAAP, Columbia University Pediatric Faculty Practice, New York, NY, and Brian Kirmse, MD, Mount Sinai School of Medicine, Department of Human Genetics, New York, NY. Review provided by VeriMed Healthcare Network.

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