Henry Levison, a Giant of Pediatric Respiratory Medicine

Henry Levison (“Henry” for his pupils), one of the universally recognized Fathers of Pediatric Respiratory Medicine, died on June 6, 2025, in Toronto, Canada, at the age of 94. He graduated from the Royal College of Surgeons, Dublin. After working as a physician in a kibbutz in the north of Israel for a few years, he came to appreciate his lack of knowledge in pediatrics and moved first to complete a residency in general pediatrics at the Michael Reese Hospital, Chicago, and then to Boston Children's Hospital, where he was introduced to respiratory physiology by Dr. Clement Smith. In the early 1960's, he was a Fellow at the Sick Children's Hospital, Toronto. His intellectual talent soon became apparent, resulting in pioneering work in mechanical ventilation of premature newborns with respiratory distress syndrome along with Maria Delivoria-Papadopoulos, under the supervision of neonatologist Dr. Paul Swyer 1-5. Together with Blair Fearon, Otolaryngologist, they were among the first to intubate and ventilate premature infants. Henry's interest in respiratory physiology prompted him to spend a training period in one of the greatest centers of this specialty, Winnipeg, Manitoba, under Dr. Rubin Cherniak. When he returned to SickKids in 1966, he joined Dr. Charlie Bryan, an authority in the field of physiology, to create a leading center for studying respiratory physiology in childhood. In recognizing the importance of precision in measurements of respiratory function and gas exchange, Dr. Levison improved the understanding of lung work in normal children and in those with respiratory diseases 6-9. Soon after, he was inspired to establish one of the first Pulmonary Function Laboratories for children. Recognizing the importance of precise reference values, he performed pulmonary function tests on thousands of children, producing the widely used “Weng and Levison” normal standards 10. During the 1970s and 80s, under his direction, the laboratory at SickKids became an internationally recognized research and training center. New pulmonary techniques and fundamental studies on airway reactivity were developed, resulting in numerous publications 11-20. Henry also emphasized robust study design, aiming for at least 100 subjects per trial—a standard humorously dubbed the “Levison Unit” before power calculations became common practice. In 1978, he became Director of the Cystic Fibrosis Clinic at SickKids, a role he held until 1995. He pioneered a multidisciplinary approach, assembling pulmonologists, physiotherapists, gastroenterologists, nutritionists, psychologists, nurses, and family counselors, and, along with Dr. Douglas Crozier, revolutionized CF care, including high-fat, high-calorie diets, achieving the world's best CF survival rates in Toronto. He also initiated the Toronto CF database with biostatistician Mary Corey, a landmark resource that enabled longitudinal studies, genotype-phenotype correlations, and contributed to the cloning of the CF gene 21-25. Recognizing the need for adult care, he laid the foundation for adult CF clinic transition programs in North America. Henry Levison's name is added to a few pioneers who gave a high contribution for the development and care of CF, such as Harry Schwachman in Boston, Leroy Matthews and Carl Doershuk in Cleveland, Warren Warwick in Minneapolis, Caroline Denning in New York, Margaret Hodson in London, John Dodge in Belfast, Jean Feigelson in Paris, Erhard Winge Flensborg in Copenhagen. From 1984 to 1994, he led the Division of Chest Diseases at SickKids, which became a global reference center for pediatric respiratory research. Clinical studies on asthma 26-32, cystic fibrosis 33-39, bronchiolitis 40, 41, croup 42, lung infections 43-46, and primary ciliary dyskinesia 47-49 established the role of pharmacologic therapies 50. His landmark work on asthma pathology first identified inflammation as a central feature 51, paving the way for anti-inflammatory treatments that transformed asthma care. During this period, he published extensively in top international journals and had an unparalleled influence on pediatric respiratory medicine worldwide. Collaborating with other Canadian leaders, he also secured recognition of Pediatric Respiratory Medicine as a Royal College subspecialty. In 1989−1990, he spent his sabbatical year at the University of Perugia, Italy. During this period, he was able to create a new scientific consciousness between pediatric respirologists by transferring enthusiasm, passion, and desire for scientific evidence, and was invited to give lectures at the main national universities. Throughout his career, Henry brought a paradigm shift that guided his research and defined the field of pediatric pulmonology. His studies advanced our understanding of childhood respiratory diseases, often challenging dogma with his legendary principle “Make things simple!” His leadership, team building, foresight, and contagious enthusiasm inspired a generation of young researchers. Henry was tireless, often arriving early in the morning and studying the latest scientific literature before his academic activities. Renowned for his incredible memory, clarity of thought, and insistence on evidence—earning him the nickname “guru of skepticism”—he demanded data before accepting new ideas. This rigor instilled confidence in his collaborators while teaching them to recognize when evidence was lacking. Despite his strictness, he was deeply respectful, warm, and humble, valuing contributions from everyone, from chief executives to the greenest medical students. Behind his occasional outspokenness, he radiated kindness and integrity. At meetings, he was a respected speaker. He had an extraordinary ability when presenting data, even the most complex ones, and was unique in openly answering questions to which he did not know the answer (“I don't know!”). Such intellectual honesty was an expression of knowledge, not of ignorance, and this is the patrimony of great minds only. Henry was a man of eclectic tastes. He loved classical music, the arts, and reading. Those who visited his apartment were able to appreciate thousands of books, vinyl albums, and CDs, and an extensive collection of drawings, including works by Matisse and Picasso. In sports, he supported the Toronto Blue Jays baseball team. Henry's legacy lies in the number of trainees who graduated under his leadership and mentorship over the years. They are now spread across the globe, many in academic positions or successful careers themselves, continuing the work he helped to inspire. Between them, the following names can be mentioned: Fernando M. de Benedictis, Gerard Canny, Khoulood Fakhoury, Dennis Gurwitz, Meyer Kattan, Alan Isles, Thomas Keens, Eitan Kerem, Thomas Kovesi, Ian McLusky, Christopher Newth, Hugh O'Brodovich, Linda Pedder, Constantine Petrou, Joe Reisman, Joseph Rivlin, Colin Robertson, Renato Stein, and Elvan Tabachnik. Apart from respiratory diseases, many of those who had the privilege of working with him learned so much outside of medicine from his personality. An episode may characterize the essence of his human value. Once, when asked about his greatest professional satisfaction, he said: “All my pupils did well.” That was Henry. Fernando M. de Benedictis: conceptualization, writing – review and editing. Eitan Kerem: conceptualization, writing – review and editing. Joe Reisman: conceptualization, writing – review and editing. The authors received no specific funding for this work. The authors declare no conflicts of interest. The data that support the findings of this study are openly available in repository name at DOI, reference number reference number.