Connective Tissue Disease–Associated Interstitial Lung Disease as a Dynamical Progression: Integrating Functional Trajectories, Imaging Quantification, and Risk Modeling in RA-ILD and SSc-ILD. Conceptual Note — URM / Dynamic Medicine Series.

This Conceptual Note is part of the URM / Dynamic Medicine Series and interprets connective tissue disease–associated interstitial lung disease as a dynamical progression rather than a static pulmonary complication. The article focuses on rheumatoid arthritis–associated interstitial lung disease and systemic sclerosis–associated interstitial lung disease as two clinically important examples where longitudinal pulmonary function, serial imaging, quantitative HRCT, progressive pulmonary fibrosis criteria, and risk models reveal measurable disease trajectory over time. It proposes that CTD-ILD progression may be understood as structured system-level drift across functional, structural, and risk-modeling domains. In this interpretation, progression is not only a decline event, but a trajectory in which immune injury, tissue remodeling, fibrotic change, imaging progression, and physiological decline become increasingly coupled. This work is conceptual and hypothesis-generating. It does not provide clinical treatment recommendations and should not be used to guide individual patient care without appropriate clinical judgment.