Clinical, functional, and radiological profile of fibrotic interstitial lung disease at high altitude: a registry-based cohort from two referral centres in Bogotá, Colombia (2,600 metres above sea level)

<title>Abstract</title> <p>Interstitial lung diseases (ILD) are a heterogeneous group of conditions characterised by variable degrees of inflammation and pulmonary fibrosis. Data from high-altitude settings, where hypobaric hypoxia may modulate disease expression and functional thresholds, remain scarce. We describe the demographic, clinical, functional, radiological, and therapeutic profile of 148 patients with fibrotic ILD (fILD) enrolled in the REPIFCO registry at two referral centres in Bogotá, Colombia (2,600 m above sea level), between 2022 and 2026. Connective tissue disease-associated ILD (CTD-ILD) was the most frequent diagnosis (36%), followed by hypersensitivity pneumonitis (HP, 26%), unclassifiable ILD (19%), and idiopathic pulmonary fibrosis (IPF, 15%). The median age was 70 years (IQR 60–75) and 59% were female. Despite a median time to diagnosis of 6 months (IQR 2–30), symptom burden was high: 56% of patients had mMRC 3–4 dyspnoea and 45% required home oxygen therapy. Pulmonary function showed a mild restrictive pattern overall; HP exhibited the greatest functional impairment. A significant clinical-radiological association was observed (χ² = 133.88; df = 18; p &lt; 0.001). These findings characterise, for the first time, a fibrotic ILD cohort from a two high-altitude referral centres in Latin America, highlighting a diagnostic and therapeutic profile that may be influenced by altitude-related physiological adaptations.</p>