In Memoriam George Alan Kaysen, MD, PhD (1943-2026).

George Alan Kaysen, MD, PhD (1943-2026), was an internationally recognized physician-scientist whose work helped define our modern understanding of protein metabolism, inflammation, and nutritional disorders in kidney disease. Over a distinguished academic career that included leadership positions at the University of California, San Francisco, the Veterans Administration Medical Center in Martinez, and the University of California, Davis, he made foundational contributions to the study of albumin kinetics, lipoprotein metabolism, nephrotic-range proteinuria, dialysis-associated metabolic derangements, protein-energy wasting, sarcopenia, and frailty. He also played major leadership roles in the International Society of Renal Nutrition and Metabolism, serving in multiple council positions, as Secretary-Treasurer, as President-Elect, and as President. He was also a member of the Editorial Boards of the Journal of Renal Nutrition and several other journals. His scholarly impact was extraordinary: approximately 290 publications, more than 18,500 citations, and three publications cited more than 1,000 times. Dr. Kaysen's scientific leadership, mentorship, and service to the international renal nutrition community left a lasting legacy that continues to shape research, clinical practice, and professional collaboration.