Dynamic Foundations of Disease XI Immune Checkpoint Inhibitor–Associated Inflammatory Arthritis as a Model of System Transition in Immune-Mediated Disease

This paper presents immune checkpoint inhibitor–associated inflammatory arthritis (ICI-IA) as a clinical model of system transition in immune-mediated disease. Unlike most autoimmune conditions, where disease onset is inferred retrospectively, checkpoint inhibition provides a defined perturbation that enables temporal observation of how the immune system shifts from regulated tolerance to persistent inflammation. In this context, ICI-IA functions as a proof-of-transition in humans. It represents one of the first clearly observable clinical models in which disease emergence can be linked to a known starting point, allowing direct study of how biological systems cross stability thresholds and reorganize into sustained inflammatory states. The analysis reframes ICI-IA not only as an adverse event, but as a dynamical shift in system behavior. By linking immunological mechanisms to system-level concepts such as instability, feedback amplification, and attractor states, the paper highlights how autoimmune disease may arise through rapid transitions rather than gradual progression. This work is part of the Dynamic Foundations of Disease series and contributes a clinically grounded example of how defined perturbations can reveal underlying transition dynamics in complex biological systems.