Background: Real-world data on patients with autoimmune interstitial lung disease (Ai-ILD) is limited.

Objectives: To describe baseline characteristics of patients with Ai-ILD in Argentina, including sociodemographic, clinical, serological, functional, and treatment features.

Methods: EPIMAR 2 is a real-life, prospective, observational, multicenter registry of patients with Ai-ILD in Argentina, initiated in April 2022. Patients > 18 years old with Ai-ILD of ? 5 years were included and classified into three subgroups: ILD associated with connective tissue disease (CTD-ILD), interstitial pneumonia with autoimmune findings (IPAF), or ILD associated with antineutrophil cytoplasmic antibodies (ANCA-ILD).

Results: 120 patients were included (73% women), with a median age of 58.6 years and a history of smoking in 65%. The subtypes were CTD-ILD (77%), IPAF (16%), and ANCA-ILD (7%). Among CTD subgroups, Systemic Sclerosis was the most prevalent (55%), followed by Rheumatoid Arthritis (31%). The most frequent serological data were antinuclear antibodies (75%), rheumatoid factor (39%), antiRo/SSa (22%), and antiCCP (15%). The most used treatments were glucocorticoids (75%), mycophenolate mofetil (44%), and methotrexate (32%). There were 41% of patients with subclinical ILD. Subclinical ILD had less functional impairment, with a median DLCO of 64% compared to 54% in symptomatic ILD.

Conclusion: We report the first baseline data on patients with Ai-ILD in Argentina in EPIMAR 2 cohort. The CTD-ILD subgroup was predominant, and subclinical ILD had less functional impairment. A Multidisciplinary approach may explain the high proportion of subclinical ILD in this cohort.