Trisomy 21

Trisomy 21, also known as 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. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8- or 9-year-old child, but this varies widely.

Causes

Trisomy 21 is caused by a mistake in cell division during the development of the egg, sperm or embryo. This results in an extra chromosome 21 in each cell. The extra chromosome disrupts the normal course of development, causing the characteristic features of Down syndrome.

Symptoms

The symptoms of Trisomy 21 can vary among individuals, but common symptoms include:

• Intellectual disability
• Delayed language and speech development
• Distinctive facial features, such as a flat face, small ears, slanting eyes, and a small mouth
• Poor muscle tone
• Short stature
• Heart defects
• Digestive problems, such as gastroesophageal reflux disease (GERD) or celiac disease
• Hearing and vision problems

Diagnosis

Trisomy 21 can be diagnosed during pregnancy through prenatal screening tests. These tests include a blood test and an ultrasound. If the screening tests indicate a high risk of Down syndrome, diagnostic tests such as amniocentesis or chorionic villus sampling can be done.

Treatment

There is no cure for Trisomy 21, but early intervention can help improve the quality of life for individuals with Down syndrome. This can include physical, occupational, and speech therapy, as well as special education programs.

See also

• Genetic disorder
• Chromosome abnormality
• Prenatal diagnosis

References

Trisomy 21 Resources
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