[Fiftieth anniversary of the trisomy 21: return on a discovery]

Abstract

Fifty years ago, I was co-author of the first paper asserting the presence of a supernumerary chromosome in Down's syndrome (called "mongolism" in France at that time). This first autosomal chromosomal abnormality was called Trisomy 21. It seemed to me historically interesting to bring my own testimony as an actor in this discovery.