Down syndrome and Trisomy 21
Down syndrome got its name in the late 19th century.
An English physician described a person with the characteristics, known now as Down syndrome in 1866 and had his work published.
His name was John Langdon Down, Down syndrome is named after him.
Down syndrome is also known as Trisomy 21.
In 1959, a French physician Jérôme Lejeune, identified Down syndrome as a chromosomal condition. He observed that individuals with Down syndrome had 47 chromosomes. A third copy of the 21st chromosome being full or partially present in these individuals.
Down syndrome and Trisomy 21 are two names used for the same chromosomal condition.