Asymptomatic autoimmune interstitial lung disease: Neither subclinical nor clinically insignificant

<bold>Background:</bold> Some patients with autoimmune interstitial lung diseases (ai-ILD) do not exhibit respiratory symptoms despite physiological and/or radiological evidence of lung involvement. The prevalence and significance of asymptomatic disease is unclear. <bold>Objectives:</bold> To determine the prevalence of asymptomatic ai-ILD and characterize this population compared to symptomatic patients. <bold>Methods:</bold> A cross-sectional study was conducted within the EPIMAR II cohort, including prospective data on 215 Argentine patients. Asymptomatic ILD was defined by lack of respiratory symptoms. Forced vital capacity (FVC), diffusing capacity (DLCO), 6-min walk test (6MWT) and high-resolution chest tomography (CT) were performed. <bold>Results:</bold> 75 patients had asymptomatic disease (prevalence 35%). No differences were observed in age or specific ai-ILD. Asymptomatic disease was more frequent in males (OR 1.85, p=0.081), and lower tobacco exposure (non-significant). FVC% was significantly higher in the asymptomatic group (74.1% vs 68%, p=0.029). There were no significant differences in DLCO%, radiologic extent or patterns (fibrotic vs non-fibrotic). Despite better lung function, 12% of asymptomatic patients desaturated in 6MWT (none had pulmonary hypertension), and 40% had >20% of radiological involvement. FVC% was higher in patients with CT extent <20% (81.8% vs 61.9%, p=0.029), and DLCO% (61.9% vs 41.9%, p=0.04). <bold>Conclusions:</bold> The prevalence of asymptomatic ai-ILD was high. Although less functional impairment, lung function remained abnormal, with significant radiological and exercise anomalies. Our study challenges the conventional classification of asymptomatic ILD as sublinical or clinically insignificant.