Down syndrome, also called Trisomy 21, is a genetic condition in which an individual has 47 chromosomes instead of 46. In most cases, an extra copy of chromosome 21 is the cause of Down syndrome. This extra copy of the chromosome affects typical mental and physical development.

Severity of Down syndrome varies from person to person, but common characteristics include:

• Decreased muscle tone at birth
• Small ears and mouth
• Upward slanting eyes
• Small stature
• Small hands and feet

Down syndrome is the most commonly occurring chromosomal condition, and according to the CDC, one in 691 babies in the United States are born with Down syndrome.

Children with Down syndrome might have delayed language development and slow motor development. Other health conditions that commonly occur with Down syndrome include congenital heart disease, hearing problems, intestinal problems (blocked small bowel or celiac disease), problems with memory or concentration, eye problems (such as cataracts), or skeletal problems.

Most individuals with Down syndrome have an intellectual disability, and they often have IQs within the mild to moderate range. Speech delays, as well as both fine and gross motor delays are common, which can also interfere with cognitive development.

Children with Down syndrome can benefit from a variety of therapies, including speech, occupational, and physical therapy. They might require special education, while many others can be integrated in a typical classroom. There is no "cure" for Down syndrome, but these therapies can help provide a person with skills for independent living.

According to the National Down Syndrome Society, life expectancy for individuals with Down syndrome has increased from age 25 in 1983 to age 60 today. Many people with Down syndrome attend school, work, live independently, maintain marriages and relationships, and contribute to society in many other ways. To read more about self-advocacy, visit the National Down Syndrome Congress.