Pioneering innovative therapies to improve the lives of those with genetic intellectual disabilities
Jérôme Lejeune Foundation

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About Jérôme Lejeune

Jérôme Lejeune was born in 1926 in Montrouge, near Paris. He studied medicine and became a researcher at the National Center of Scientific Research (CNRS) in Paris in 1952. Dr. Lejeune was also the founder of the first specialized clinic for Trisomy 21 patients at Necker Children’s Hospital in Paris.

In July 1958, as he was studying chromosomes linked to Down syndrome, he discovered the existence of an additional chromosome on the 21st pair. With this remarkable and ground-breaking discovery, he renamed the condition trisomy 21 to accurately describe the genetic abnormality. For the first time Dr. Lejeune had established a link between an intellectual disability and its genetic cause. Dr. Lejeune would go on to discover the genetic cause of Cri-du-Chat syndrome and to also advance understanding of Fragile X syndrome and others.

In recognition of his discovery, in 1964 Jérôme Lejeune was named the first Professor of Fundamental Genetics at the Faculty of Medicine of Paris. While increasing his research he continued to remain available to families, caring for disabled children, and to travel the world giving thousands of lectures on genetics. As a well-known geneticist, he was called to the United States to testify in court in Davis v. Davis, the Tennessee Frozen Embryo Case, in Maryville, Tennessee in 1989.

Jérôme Lejeune received numerous awards and was elected as a member of several academies. In 1962 he was honored in Washington, D.C. by President John F. Kennedy with the first Kennedy Prize for his research into genetic intellectual disability and for finding the genetic cause of Down syndrome. In 1969 he received the William Allen Award from the American Society of Human Genetics – the highest award possible for a geneticist.

Jérôme Lejeune died April 3, 1994, shortly after being appointed by Pope John Paul II to serve as the first president of the Pontifical Academy for Life.

Each year on the anniversary of his passing, a Mass is held in a large parish of Paris. The testimony of his life continued to inspire the work of doctors and researchers.

For more information about Jérôme Lejeune, please visit There is also a charming biography written on Jérôme Lejeune by his daughter, Clara Lejeune Gaymard, called Life is a Blessing which may be ordered from