Down Syndrome

Down Syndrome is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability.

Causes

Down Syndrome is caused by having three copies of the genes on chromosome 21, rather than the usual two. The parent who provides the extra chromosome can be either the mother or the father. There is no known behavioral activity or environmental factor that changes the possibility.

Symptoms

People with Down Syndrome may have some or all of these physical characteristics: a small chin, slanted eyes, poor muscle tone, a flat nasal bridge, a single crease of the palm, and a protruding tongue due to a small mouth and relatively large tongue. These individuals may have a short neck and small hands and feet.

Diagnosis

Down Syndrome can be identified during pregnancy by prenatal screening followed by diagnostic testing, or after birth by direct observation and genetic testing. Since the introduction of screening, pregnancies with the diagnosis are often terminated.

Treatment

There is no cure for Down Syndrome. Education and proper care have been shown to improve quality of life. Some children with Down Syndrome are educated in typical school classes, while others require more specialized education. Some individuals with Down Syndrome graduate from high school, and a few attend post-secondary education.

Prognosis

The average IQ of a young adult with Down Syndrome is 50, equivalent to the mental ability of an 8 or 9-year-old child, but this varies widely.

Epidemiology

Down Syndrome occurs in about 1 per 1,000 babies born each year. The number of pregnancies with Down Syndrome is much higher due to the high rate of miscarriage. Maternal age affects the chances of conceiving a baby with Down Syndrome.

See Also

• Genetic disorders
• Chromosome 21
• Intellectual disability

References

Down Syndrome Resources
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