Peter James Dyck: In Memoriam

Dr. Peter James Dyck died peacefully on Saturday, July 26, 2025, in Rochester, MN, surrounded by his family. Peter had a remarkable and fulfilling life and by the time of his retirement in December 2024, at 97 years of age, he was the oldest and longest-serving member of staff in the history of the Mayo Clinic. Peter was born in a small Mennonite village, Neue Hoffnung (New Hope), in Southern USSR in 1927. When Peter was 2 years old, his family fled (as they were not Russian), emigrating to Canada, settling on the prairies of Saskatchewan and spending their first winter in a sod house. His mother died when he was 13 years old. In high school, Peter worked at a hardware store to support his family. Because Peter wanted an education, he worked in a bowling alley setting up pins, a sawmill cutting lumber, and mining peat which he remembered as being “back breaking work.” Dr. Dyck attended the University of Saskatchewan. While there he spent three summers as the lead on a limnobiology field team in Lac La Ronge, a Northern Saskatchewan lake. This experience, under the direction of Dr. Donald Rawson, set the foundation for the rest of his career by teaching him scientific methods and the importance of quantification for studying biological observations. Peter was very proud that his work contributed to protecting the lake trout population by setting fishing limits. Dr. Dyck started medical school at the University of Saskatchewan and completed the clinical years at the University of Toronto. Following an internal medicine residency, he became the first neurology resident at the University of Saskatchewan. Peter then did neurology fellowship training in neurology at Mayo Clinic in Rochester, MN, and joined the Mayo Clinic staff in 1961. Dr. Dyck's long and distinguished career spanned seven decades with international recognition as a preeminent clinician, investigator, and educator in the field of peripheral nerve disease. Dr. Dyck studied the natural history and pathophysiologic alteration in peripheral nerves with development in health and with diseases using clinical, genetic, and pathophysiologic studies and treatment trials. His first major contribution was the separation of Charcot–Marie–Tooth (CMT) into demyelinating (Type 1) and neuronal (Type 2) forms. Dr. Dyck had the first large series of a form of inflammatory neuropathy from demyelination that made patients very weak that he named chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). He defined the pathology of vasculitic neuropathy showing that vasculitis occurs at all levels of the vasculature within the nerve but that the nerve infarction starts at the watershed zone of nerve perfusion. He conducted some of the first controlled trials in neurology on CIDP using prednisone, plasma exchange (using sham plasma exchange as a control) and intravenous immunoglobulin. Other diseases studied by Peter Dyck include diabetic sensorimotor polyneuropathy, neuropathy associated with monoclonal gammopathy of undetermined significance (MGUS), hypothyroid-associated peripheral neuropathy, and hereditary transthyretin amyloidosis polyneuropathy. Peter did a large epidemiological study, the Rochester Diabetic Neuropathy Study, looking at types, frequency and severity of neuropathies associated with diabetes mellitus. A 1993 epidemiological paper from this study was named a Hallmark Paper by the NEUROdiab study group in 2025 shortly before Peter's death. The guiding principle in Dr. Dyck's life and career was the marked, unrelenting pursuit of truth. Peter strove to understand truth as best he could, and the pursuit of truth was a driving force in his personal and scientific life. Truth was so important to Peter that on one occasion early in his career he submitted a manuscript which was accepted and ready for publication. An attempt to verify some of the data left him with concerns and before it could be published, he asked the journal editor to stop publication. He eventually performed a different experiment to confirm the validity of his findings. Dr. Dyck's experience collecting biological measurements on fish inspired him to create standard methods to study neurological disease, especially peripheral neuropathy. He often said that his whole career could be summarized by his efforts to identify ways to quantify biological observations. With this pursuit of quantitation to obtain truth, he developed and introduced the use of nerve biopsy. Previously, nerve pathology had been done on autopsy specimens but had rarely been performed on living patients. He reintroduced teased nerve fibers a technique that allows pathological abnormalities to be followed along the length of individual nerve fibers and created a grading system for them. He developed a quantitative method for looking at nerve fiber size histograms on nerve biopsies. Peter developed quantitative sensory testing by which he measured patients' ability to feel vibration, touch, cool, and heat pain and developed normal controls for the different sexes and age populations. He also developed neuropathy grading scales to quantify how severe neuropathy is, and these include the neuropathy impairment score (NIS) and the modified neuropathy impairment score plus 7 (mNIS+7). These scales have been used in many treatment trials and provided the first successful measurements of drug efficacy in TTR Amyloid Polyneuropathy (a previously incurable disease). Peter was thrilled that these studies led to FDA approval for life-saving medicines and that his scales provided the evidence of these drugs' effectiveness. Dr. Dyck wrote over 460 peer-reviewed articles, 129 book chapters, and 27 reviews. He was the editor of four editions of Peripheral Neuropathy (Saunders/Elsevier) considered by many to be the standard textbook for peripheral nerve disease. Peter edited four other books on peripheral neuropathy. Dr. Dyck was a founding member of the Peripheral Nerve Study Group and of the Peripheral Nerve Association eventually merging into the Peripheral Nerve Society. He served as President of the American Neurological Association and the Peripheral Nerve Association. Dr. Dyck's remarkable accomplishments in the field of peripheral neuropathy were recognized with numerous awards and Honors including the Roy E. and Merle Meyer Professor of Neuroscience, Mayo Clinic Distinguished Investigator Award (2004), Mayo Clinic Distinguished Alumnus Award (2007), and Teacher of the Year Award in the Department of Neurology (1996). He was honored to be the Wartenberg Lecturer at the American Academy of Neurology, the Robert S. Schwab Award from the American Clinical Neurophysiology Society in 2023 and received the Neurodiab Lifetime Achievement Award and the Albert Nelson Marquis Achievement Award. He was an Honorary Member of several organizations including the American Academy of Neurology, American Neurological Association, American Association of Electrodiagnostic Medicine, Canadian Society of Clinical Neurophysiologists, European Neurological Society, and the Mexican Neurological Association. Dr. Dyck mentored approximately 150 international fellows in the field of peripheral neuropathy. He has inspired and educated generations of healthcare professionals. His legacy will live on in the outstanding clinical and pathological training he provided. Peter was a superb and fair but hard mentor and colleague. Because of his very high standards, he was a demanding person yet very encouraging and respectful of good work and strong ideas. Although Peter could be a harsh critic, he could also be convinced when he was wrong. Many people discouraged his son, P. James, from working directly with him because he had such a strong personality and they worried the situation might cause discord and stunt his son's development. But the relationship was a very fulfilling and productive one. Peter and P. James worked together for over 30 years and had many productive discussions and collaborations on the peripheral nerve pathophysiology that resulted in many publications. During his time at University, Peter met a high-spirited intellectual woman, Isabelle Bonham. Peter and Isabelle created an enduring and unique partnership that lasted for over 70 years. They both had a strong intellectual curiosity that inspired them to have debates about religion, literature, and politics with each other—there was never a dull moment around the dinner table. Peter and Isabelle have four children: Ernie, Fred, P. James, and Kate. Besides work, Peter loved classical music and considered pursuing a career in music. His life-long love of music resulted in providing encouragement and financial and support for many musicians and music organizations, especially in baroque and organ music. For more than 40 years, he took his peripheral nerve fellows to weekly summer organ concerts at local churches. Peter Dyck also loved spending time on his farm on the Mississippi River. He purchased his farm from one of his Charcot Marie Tooth patients and he would spend his weekends there with his family and friends, playing farmer on his tractor, and writing his papers with the music of Johann Sebastian Bach playing at loud volumes in the background. Dr. Peter J. Dyck had an amazing, fulfilling, productive and happy life and he stayed true to his principles about the use of quantitative endpoints being one way to pursue truth. He did not dwell on his past accomplishments; rather he was thinking about his next project. When asked what his favorite contribution to Neurology was he would always answer it was the project that he was currently working on. At the end, Peter was very pleased that many of the quantitative endpoints that he had developed showed efficacy in clinical trials that led to meaningful neurological improvement in conditions like hATTR amyloid polyneuropathy and led to FDA approval of these medications. Dr. Dyck will be missed by family, friends, and colleagues, and all others who had the fortunate opportunity to know him.

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