Down Syndrome

(DS; Trisomy 21)

Definition

Down syndrome is a genetic problem that can cause birth defects, problems learning, other health issues. There are three types:
  • Trisomy 21 (most common)
  • Translocation
  • Mosaicism

Causes

Down syndrome is a problem with chromosome 21. Each type of Down syndrome has its own genetic change:
  • Trisomy 21 is when there is an extra copy of chromosome 21 because of a problem that happens when cells divided in the egg or sperm
  • Translocation is an inherited type that happens when a part of chromosome 21 breaks off and reattaches to another chromosome
  • Mosaicism is an extra copy of the chromosome in only some cells

Risk Factors

Mothers who are older than 35 years of age are at higher risk. Translocation is more common in people who have other family members with it.

Symptoms

Babies born with Down syndrome may have:
  • Weak muscles
  • A short neck with loose skin at the back
  • Flat facial features
  • A small head, ears, and mouth
  • Eyes that slant up
  • White spots on the colored part of the eye
  • Short hands with short fingers
  • A single skin line in the palm of the hand
  • More space between the big toe and second toe
  • A tongue that sticks out
A person will also have problems with thinking and learning. They are also at risk for other problems, such as:

Diagnosis

The doctor may suspect Down syndrome based on a child's features at birth. A blood test will be done to confirm it.
Down syndrome may be suspected before birth using prenatal screenings, such as:
  • Blood tests of the mother to look for markers of Down syndrome
  • An ultrasound to look for features in the baby's neck
The diagnosis can be confirmed before birth by testing a baby's DNA. This can be done with
  • Amniocentesis to test the fluid in a mother's womb
  • Chorionic villus sampling (CVS) to test tissue from the placenta
Amniocentesis
Fetus Chromosomes
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Treatment

There is no cure for Down syndrome. Young children and their families may benefit from early intervention. Older children will need special education services. Most adults go on to lead active lives. Some people with Down syndrome live with family. Others live with friends or on their own.
Children and adults may also benefit from:
  • Speech therapy
  • Physical therapy
  • Occupational therapy to help with activities of daily living
  • Mental health counseling
A person's medical team will also need to watch for signs of related issues, such as heart problems and hearing loss.

Prevention

There are no known guidelines to prevent Down syndrome.

RESOURCES

National Down Syndrome Congress  http://www.ndsccenter.org 
National Down Syndrome Society  http://www.ndss.org 

CANADIAN RESOURCES

Canadian Down Syndrome Society  http://www.cdss.ca 

References

Bull MJ, Committee on Genetics. Health supervision for children with Down syndrome. Pediatrics. 2011 Aug;128(2):393-406full-text, correction can be found in Pediatrics 2011 Dec;128(6):1212.
Down syndrome. EBSCO DynaMed website. Available at:  https://www.dynamed.com/condition/down-syndrome  . Updated March 17, 2017. Accessed April 6, 2020.
Down Syndrome. National Institute of Child Health and Human Development website. Available at: http://www.nichd.nih.gov/health/topics/down/Pages/default.aspx. Updated June 21, 2018. Accessed April 6, 2020.
Kazemi M, Salehi M, Kheirollahi M. Down syndrome: current status, challenges, and future perspectives. Int J Mol Cell Med. 2016;5(3):125-33.

Revision Information

  • Reviewer: EBSCO Medical Review Board Rimas Lukas, MD
  • Review Date: 02/2020
  • Update Date: 04/06/2020