Longitudinal change of idiopathic inflammatory myopathy-associated interstitial lung disease on high-resolution computed tomography, a prospective cohort study

This study aimed to investigate longitudinal change of idiopathic inflammatory myopathy-associated interstitial lung disease (IIM-ILD) on high-resolution computed tomography (HRCT). This prospective cohort study was undertaken involving 514 IIM-ILD patients (367 females; median age 54 years) from 2016 to 2022. Deep learning algorithms were employed to quantify interstitial lesions on HRCT, while clinical parameters including pulmonary function tests, serum biomarkers, and arterial blood gas analysis were also considered. The study identified anti-MDA5 antibody positivity (OR: 10.46, 95% CI: 3.40–32.22), reduced FVC (OR: 0.91, 95% CI: 0.84–0.98), and extensive ground-glass opacity (GGO) (OR: 1.07, 95% CI: 1.01–1.13)/ reticulation (OR: 1.23, 95% CI: 1.07–1.41) involvement as independent risk factors for rapidly progressive interstitial lung disease (RP-ILD) within IIM. During the rapid progressive period of RP-ILD, anti-MDA5-positive dermatomyositis (MDA5 + DM) showed greater progression in fibrotic, inflammatory, and emphysema lesions compared to anti-synthetase syndrome (ASS). In the slow progressive period, MDA5 + DM tended towards chronic fibrosis, while ASS exhibited overall improvement. The extent of lesion increase in non-RP-ILD patients is significantly smaller than in those who have experienced RP. Reticular and consolidation changes were strongly correlated with variations in VC%, FVC%, and FEV1%, and moderately associated with changes in TLC and DLCO. The prognostic impact of GGO proportion on adverse outcomes intensified with longer follow-up durations, with each 1-unit increase in whole-lung GGO proportion linked to a 0.56% higher risk of adverse outcomes (HR: 1.0056, 95% CI: 1.001–1.010). IIM-ILD cases with prior rapid progression will develop chronic fibrotic trajectories with persistent inflammation compared to non-progressive cases. ASS is characterized by sustained inflammatory activity in imaging manifestations, whereas MDA5 + DM shows post-acute fibrotic remodeling following initial injury. Longitudinal GGO emerges as a critical prognostic indicator, demonstrating time-dependent cumulative risk effects.