EVITA is a multicentric Latin-American prospective cohort on chronic hypersensitivity pneumonitis. EVITA's objective is to identify phenotypes and/or endotypes associated with different disease trajectories measured primarily by forced vital capacity (FVC) during a 24 month follow-up period. Other secondary measures of disease progression will also be investigated such as imaging, time to death or lung transplantation, and patient-reported outcomes

Inclusion Criteria:

1. Adult outpatient subjects (18 years old or older) that fulfill the 2020 ATS/JRS/ALAT diagnostic criteria of HP of at least moderate confidence (70% confidence or more).
2. Willingness to undergo the evaluations proposed in this protocol
3. HP diagnosis within the last 24 months
4. Presence of radiological or histological fibrosis:

4.a. Radiological fibrosis consists of unequivocal fine or coarse reticulation with architectural lung distortion and/or traction bronchiectasis and/or honeycomb.

4.b. Unequivocal histopathological fibrosis evidenced on lung specimens

Exclusion Criteria:

1. Pregnancy
2. Presence of established connective tissue disease
3. Severe comorbidity impacting on the respiratory system as judged by the attending physician (ex. congestive heart failure, neoplasm, post-COVID-19 sequelae)
4. Use of supplemental oxygen at rest
5. Dyspnea mMRC 4 (too breathless to leave the house or breathless when dressing or undressing)
6. Unequivocal emphysematous pattern of HP on HRCT
7. Unequivocal pleuro-parenchymal fibroelastosis on the HRCT
8. Significant pulmonary arterial hypertension:

8.a. Signs of right ventricular failure by echodopplercardiogram or 8.b. Cardiac index < 2L/min/m2 or right heart catheterism

Adult patients with chronic (fibrotic) hypersensitivity pneumonitis