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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-Ãtienne Dominique Esquirol in 1838 and Ãdouard SÃ©guin in 1844. In 1957, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered.
Who Discovered Down Syndrome. Down syndrome is a chromosomal disorder that produces a set of mental and physical symptoms. It is caused by an extra copy of chromosome 21. In a person with Down syndrome there are three copies of the chromosome 21, one from the father, one from the mother and a third copy.The extra copy of this chromosome changes the development of the brain and body.Down syndrome affects about 1 in every 800 babies.r Down could not identify what caused the condition and it was not until 1959 that a Professor named Jerome JÃ©rome lejeune discovered That down syndrome was caused by a chromosomal. Irregularity he found that in people With down syndrome an extra chromosome was. present