What is Trisomy 21 (Down syndrome)?

Trisomy 21, also known as Down syndrome, is a condition that causes intellectual disability and a wide range of medical problems. It occurs when there are three copies of chromosome 21 in the cells of the body instead of two. The symptoms seen in Down syndrome are a result of this extra material impacting the growth and development of an affected individual.

The symptoms of Down syndrome vary greatly. Common features include mild to moderate intellectual disability, delays in development, unique facial features, and low muscle tone. Many other medical conditions—such as heart defects, gastrointestinal issues, hearing loss, and vision problems—can also be seen. The average life span for someone with Down syndrome is now over the age of 60, although this does depend on the severity of an individual’s specific health issues.

How common is Trisomy 21 (Down syndrome)?

The incidence of Down syndrome in the population is 1 in 800 live births.

How is Trisomy 21 (Down syndrome) treated?

Treatment for Down syndrome is directed at managing the specific needs of each individual. This often means receiving care through a team of specialists that may include physicians, speech pathologists, occupational therapists, physical therapists, and social workers. Infants and children diagnosed with Down syndrome will often benefit from receiving early intervention and other supportive services beginning at a young age.

What is the prognosis for an individual with Trisomy 21 (Down syndrome)?

Outcomes for people with Down syndrome have improved significantly in the past 40 years. On average, most individuals who receive appropriate medical care will live into their sixties.

Other names for
Trisomy 21

  • Down syndrome


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