Down syndrome

What is Down syndrome?

A total autosomal trisomy that is caused by the presence of a third (partial or total) copy of chromosome 21 and that is characterized by variable intellectual disability, muscular hypotonia, and joint laxity, often associated with a characteristic facial dysmorphism and various anomalies such as cardiac, gastrointestinal, neurosensorial or endocrine defects.

Other condition names

  • Trisomy 21

Inheritance type

Not applicable


  • Worldwide: 1-5 in 10,000
  • Europe: 1-5 in 10,000

Age of Onset

  • Antenatal
  • Neonatal
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