Prevalence, Clinical Features and Functional Outcomes of Hypersensivity Pneumonitis: a real-life analysis in the Province of South Tyrol - Italy

<bold>Background:</bold> Hypersensitivity pneumonitis (HP) is a complex interstitial lung disease caused by an immune response to inhaled antigens, encompassing fibrotic and non-fibrotic phenotypes, which significantly influence patient prognosis. This study examines HP's epidemiology, clinical features, and outcomes in South Tyrol, Italy. <bold>Methods:</bold> retrospective analysis at a single-center outpatient clinic from 2016 to 2021. We included patients with confirmed diagnoses of HP, while excluding cases of other interstitial lung diseases or those with uncertain diagnoses. Demographic data, exposure history, phenotypes, pulmonary function tests (PFT), computed tomography (CT) imaging and outcomes at 1 and 3 years were assessed. <bold>Results:</bold> The cohort comprised 47 patients, most of whom had occupational exposures in farming. Fibrotic phenotype emerged slightly more frequently (53.8%). Disease prevalence stood at approximately 12.2 cases per 100,000 in rural regions versus 3 per 100,000 in urban regions. Over a span of 1 to 3 years, survivor outcomes demonstrated disease stability, as shown by PFTs and CT scans. Five patients (10.6%) deceased at 3 year follow up. <bold>Conclusions:</bold> This study highlights disease association with occupational exposure especially in rural settings, suggesting high prevalence numbers in this specific region. Over a three-year period, disease stability was noted among survivors, yet follow-up data were limited Our findings highlight the necessity of establishing regional prevalence rates for rare diseases, thereby facilitating the development of targeted interventions to mitigate risk factors or behaviors within vulnerable populations.