In the name of the Father, and of the Son, and of the Holy Spirit,
Peace be with you!

Dear members of the Foundation,
Dear family members of the Venerable Professor Jérôme Lejeune,
Dear friends,

It is a joy to celebrate with you the centenary of the birth of Jérôme Lejeune, together with the members of the Foundation that bears his name and continues his work.

Deeply moved by the suffering of children with disabilities, Professor Lejeune devoted his life as a scientific researcher to them. His most famous discovery—the chromosomal abnormality responsible for Trisomy 21—made him a pioneer of modern genetics. He was recognized throughout the world, a fact witnessed by the long list of honors he received. But he was also a physician by vocation and never ceased working to find a cure to alleviate the suffering of his patients, whom he called "the poorest of the poor." He passionately defended the life and dignity of the most vulnerable, even at the cost of his own career. He loved to say: "Medicine is the hatred of disease and the love of the patient."

Pope Saint Paul VI, who was aware of Professor Lejeune's academic excellence and tireless dedication to the Church, appointed him a member of the Pontifical Academy of Sciences. Later, as you know, his deep friendship with Saint John Paul II and their shared commitment to the defense of life led to the establishment of the Pontifical Academy for Life, which Professor Lejeune regarded as a necessary institution in the face of the growing threats against human life.

A man of science and wisdom, Jérôme Lejeune soon realized that his scientific discovery would be used to eliminate people with Down syndrome before they were born. He did not hesitate to become their defender, denouncing the violation of the Hippocratic Oath and what he called the new eugenics, describing it as "chromosomal racism." His prophetic witness led him to defend the life of every human being in the name of the inviolable dignity that originates in God's creative act. In this regard, he advised and challenged institutions and rulers throughout the world. That struggle brought him harsh criticism in certain scientific circles.

Professor Lejeune understood that while technology can assist medicine, it can never replace it. He also knew that technology can be used against medicine—which by its very nature is at the service of life—whenever it escapes essential ethical oversight and is governed instead by calculations of efficiency, profitability, or utility. But the value of the human person does not depend on what he or she accomplishes or produces. For this reason, a physician should never be allowed to decide of the life of a particular embryo or a particular elderly person, on the basis of laboratory algorithms! Medicine must never become the servant of programmed death!

Dear friends, today the Lejeune Foundation, of which you are active members, continues the work begun by Professor Lejeune in the three areas of research, care, and the unconditional defense of the human person. I rejoice in the place you occupy worldwide in research on genetically based intellectual disabilities. You have also established and supported the Jérôme Lejeune Institute, which provides consultations for thousands of patients affected by various intellectual disabilities.

I wish to express my encouragement for your commitment to life and human dignity, particularly in your work with public authorities. I know that you regularly take part in social debates in order to protect every person in every circumstance of life. I also know that you are committed to promoting a culture of life through the International Chair of Bioethics, which provides academic formation for professionals in this field: healthcare workers, jurists, and philosophers. I thank you for this formation, which prepares men and women who, tomorrow, will help ensure that medical ethics remain at the service of human dignity and life.

To you, dear friends with Down syndrome and to your families; to you, the children of the Venerable Professor Lejeune present here this morning; to all of you, members of the Jérôme Lejeune Foundations in Spain, Argentina, and the United States; and finally to those of you who have come from Portugal, Italy, Tunisia, Côte d'Ivoire, and Korea, I wish to express my appreciation for the work that you, as lay faithful, carry forward in the charity of truth, following in the footsteps of the Venerable Jérôme Lejeune. Be committed witnesses in society, like him, and serve the constant pursuit of the common good. This is the first great principle of the Church's social teaching and of the "social form" of the dignity recognized in every person (Magnifica humanitas, no. 59). The common good excludes no one who has been created in the image and likeness of God.

The message and work of the Venerable Jérôme Lejeune are founded on the universality of reason and heart united together. May his example inspire courage in the truth among the many young people and professionals who long for integrity. May it help them to unite, without rigidity, reason and faith, words and deeds, freedom from judging persons, and the rejection of falsehood.

I entrust you to the intercession of Our Lady, asking her to guide your steps, sustain your efforts, and spread her tenderness over all those who are vulnerable. To all of you present here I gladly impart my Apostolic Blessing, which I also extend to all the members of the Foundation, to their families, and to Jérôme Lejeune's "dear protégés."

Thank you.

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Holy See Press Office Bulletin, 23 June 2026