Radiological diversity in rheumatoid arthritis associated with usual interstitial pneumonia (RA-UIP) and its therapeutic implications: towards a generalizable framework of interstitial lung disease treatment

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is a major extra-articular manifestation of rheumatoid arthritis and a key determinant of patient outcomes. Among its radiologic subtypes, the usual interstitial pneumonia (UIP) pattern is the most frequent and clinically important; however, the definition and conceptual use of "RA-UIP" differ among disciplines and across countries, reflecting variations in how radiologic and pathologic features are integrated into clinical practice. RA-UIP shares several features with idiopathic pulmonary fibrosis (IPF) but also differs in pathogenesis, imaging characteristics, and clinical behavior, resulting in more heterogeneous prognoses and therapeutic responses. Although a recent international update proposed a unified classification encompassing both idiopathic and secondary interstitial pneumonias, secondary UIPs such as RA-UIP often show overlapping or combined morphologies that remain challenging to categorize and manage. This review emphasizes the dynamic interplay between joint and lung disease activity in RA-ILD conceptualized as a "virtuous" or "vicious" cycle. Stable control of arthritis can promote pulmonary stability, whereas uncontrolled systemic inflammation and treatment limitations-often complicated by infection-can destabilize both. While antifibrotic therapy can slow fibrotic progression, sustained inflammatory control remains essential for maintaining a favorable cycle. Integrating these dual perspectives, we outline a conceptual clinical-radiologic framework for interpreting UIP-like patterns in RA-ILD in relation to the balance between inflammation and fibrosis. Rather than serving as an evidence-based treatment algorithm, this flexible, patient-centered framework is intended to organize radiologic heterogeneity, support multidisciplinary therapeutic discussion, and generate hypotheses for future validation across autoimmune and other fibrosing ILDs.