Downs syndrome
| Down syndrome | |
|---|---|
| Synonyms | Down's syndrome, Down's, trisomy 21 |
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| A boy with Down syndrome assembling a bookcase | |
| Specialty | Medical genetics, pediatrics |
| Symptoms | Delayed physical growth, characteristic facial features, mild to moderate intellectual disability |
| Causes | Third copy of chromosome 21. |
| Risk factors | Older mother |
| Diagnostic method | Prenatal screening, genetic testing |
| Treatment | Educational support, sheltered work environment |
| Prognosis | Life expectancy 50 to 60 (developed world) |
| Frequency | 5.4 million (0.1%) |
| Deaths | 26,500 (2015) |
| Classification | |
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| External resources |
Down syndrome (DS or DNS), also known as trisomy 21, 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 ability of an 8- or 9-year-old child, but this can vary widely.
The parents of the affected individual are typically genetically normal. The extra chromosome occurs by chance. The possibility increases from less than 0.1% in 20-year-old mothers to 3% in those age 45. There is no known behavioral activity or environmental factor that changes the possibility. 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. Regular screening for health problems common in Down syndrome is recommended throughout the person's life.
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. In adulthood, about 20% in the United States do paid work in some capacity with many requiring a sheltered work environment. Support in financial and legal matters is often needed. Life expectancy is around 50 to 60 years in the developed world with proper health care.
Down syndrome is one of the most common chromosome abnormalities in humans. It occurs in about one per 1000 babies born each year. In 2015, Down syndrome was present in 5.4 million individuals and resulted in 27,000 deaths down from 43,000 deaths in 1990. It is named after John Langdon Down, the British doctor who fully described the syndrome in 1866. Some aspects of the condition were described earlier by Jean-Étienne Dominique Esquirol in 1838 and Édouard Séguin in 1844. In 1957, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered.
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