Jérôme Lejeune

Jérôme Jean Louis Marie Lejeune, a French pediatrician and geneticist, is most recognized for identifying the chromosomal causes of Down syndrome (trisomy 21) and cri du chat syndrome. He later became a prominent opponent of using amniocentesis for prenatal testing when it led to selective abortion for eugenic reasons. In 2021, Pope Francis declared him Venerable.

In 1958, while working in Raymond Turpin’s laboratory alongside Marthe Gautier, Lejeune reported that Down syndrome resulted from an extra copy of chromosome 21. His laboratory notebooks show he made this observation on 22 May 1958. The French Academy of Sciences published the discovery with Lejeune as first author, Gautier as second, and Turpin as senior. In 2009, Gautier claimed she had prepared the fibroblast tissue samples and first noticed the abnormal chromosome count. This was the first time a chromosomal abnormality was linked to an intellectual disability.

Lejeune joined Turpin’s department in the early 1950s, focusing on Down syndrome’s causes. By 1953, they had connected an individual’s characteristics to their dermatoglyphs—fingerprints and hand lines—which form during early embryo development. Studying the hands of children with Down syndrome, they deduced these anomalies appeared during embryonic formation. In 1956, Swedish biologists confirmed humans have 46 chromosomes. Turpin had earlier proposed culturing cells to count chromosomes in trisomy. Gautier, recently joining Turpin’s pediatrics group at Armand-Trousseau Hospital, offered to attempt this, having learned cell culture and tissue staining in the United States. Turpin provided tissue samples from Down syndrome patients. With limited resources, Gautier set up France’s first in vitro cell culture lab and discovered the chromosome discrepancy.

The hospital lacked a microscope for capturing slide images, so Gautier entrusted her slides to Lejeune, a CNRS researcher, who photographed them in a better-equipped lab. In August 1958, the photos identified the extra chromosome in Down syndrome patients. Lejeune’s notebook, started on 10 July 1957, shows that on 22 May 1958 he first demonstrated 47 chromosomes in a child with Down syndrome, two years after Tjio and Levan proved humans have 46 chromosomes. On 13 June 1958, he identified another case, and a karyotype photo met skeptical interest at the International Congress of Genetics in Montreal. The full impact came on 26 January 1959, when the French Academy of Sciences published the team’s first paper on three cases. In January 1959, to preempt similar English research, the Trousseau lab announced results in the Academy’s Proceedings, with Lejeune first author, Gautier second (her name misspelled as “Gauthier”), and Turpin last. On 16 March 1959, a presentation covering nine cases confirmed the findings. In April 1959, the English team of Brown and Jacobs corroborated the results, citing the January 1959 publication. “Mongolism” became trisomy 21, opening a new field: cytogenetics.

Gautier has criticized Lejeune being portrayed as the sole discoverer. In interviews and a 2009 article, she stated she developed the cytological and histological resources alone, preparing slides showing trisomy, and that Lejeune took her slides under the pretense of photographing them but presented them as his own. Jean-Marie Le Méné, president of the Jérôme Lejeune Foundation, maintains no evidence shows Gautier made the key discovery. Gautier does not dispute that Lejeune identified the extra chromosome as chromosome 21, but insists she first noticed the abnormal count. In a 5 November 1958 letter, Lejeune thanked her for her “preparations” instrumental to the discovery, and she appeared as co-author on two seminal papers: one on trisomy 21 and another on the cell culture techniques she learned during a 1955–1956 Harvard scholarship.

Continuing his genetics work, Lejeune described other chromosomal diseases. In 1963, he identified cri du chat syndrome, caused by a deletion on chromosome 5.