Jérôme Lejeune

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Lore & Background

In 1958, while working in Raymond Turpin’s laboratory with Marthe Gautier, Jérôme Lejeune reported that he had discovered that Down syndrome was caused by an extra copy of chromosome 21. According to Lejeune's laboratory notebooks, he made the observation demonstrating the link on 22 May 1958. The discovery was published by the French Academy of Sciences with Lejeune as first author, Gautier as second author, and Turpin as senior author. In 2009, co-author Gautier claimed that the discovery was based on fibroblast tissue samples that she had prepared and on which she noticed the discrepancy in chromosome count. This discovery was the first time that a defect in intellectual development was shown to be linked to chromosomal abnormalities. Gautier does not dispute that Lejeune identified the 47th chromosome as an extra copy of chromosome 21, but maintains that she was the first to notice the abnormal count. In a personal letter from 5 November 1958 to Gautier, Lejeune wrote appreciatively about her 'preparations' that were instrumental to the discovery.

Reader's Guide

Continuing his work in genetics, Lejeune described several other diseases related to chromosomal abnormalities. In 1963 he identified Cri du Chat syndrome, caused by a missing segment in the short arm of chromosome 5, and in 1966 he described 18q-Syndrome, which results from loss of the distal portion of the long arm of chromosome 18. Lejeune also discovered the Dr phenotype and identified trisomies on chromosome 9 in 1970 and chromosome 8 in 1971. In 1969, Lejeune's work earned him the William Allan Award from the American Society of Human Genetics. As of 2013 he was the only Frenchman to have won it. Although Lejeune's discoveries paved the way for new therapeutic research, they also led to the development of prenatal diagnosis of chromosome abnormalities and thence to abortions of affected pregnancies. This was very distressing to Lejeune, a devout Catholic, and led him to begin his fight for the anti-abortion cause. After receiving the Allan prize, Lejeune gave a talk to his colleagues which concluded by explicitly questioning the morality of abortion. In a letter to his wife, Lejeune wrote 'today, I lost my Nobel prize in Medicine.' He later developed a close relationship with Pope John Paul II and served as president of the Pontifical Academy for Life for only a few weeks before his death in April 1994.

Did You Know?

• Lejeune's laboratory notebook shows he demonstrated the presence of 47 chromosomes in a child with Down syndrome on 22 May 1958.
• In 1963 Lejeune identified Cri du Chat syndrome, caused by a missing segment in the short arm of chromosome 5.
• Lejeune wrote to his wife after a talk questioning abortion: 'today, I lost my Nobel prize in Medicine.'
• He was declared Venerable by Pope Francis on 21 January 2021.
• Lejeune served as president of the Pontifical Academy for Life for only a few weeks before his death.