English edit

 
A father and his son with Down syndrome

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Etymology edit

Named after John Langdon Haydon Down (1828–1896), an English physician who first described the condition as a distinct form of mental disability in the 1860s.

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Proper noun edit

Down syndrome

  1. (neurology, chiefly US, Australia, New Zealand) A genetic disorder caused by the presence of all or part of a third copy of chromosome 21 (a chromosomal excess), whereby the patients typically have a delay in cognitive ability and physical growth, as well as a small head and tilted eyelids. [from 1961.]

Usage notes edit

The condition is known only as Down's syndrome in the UK and Canada.

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