Sub-study of the main Pulmonary Fibrosis Biomarker (PFBIO) cohort (NCT02755441), recruiting patients with an MDT-diagnosis of hypersensitivity pneumonitis (HP). Patients are included for the collection of blood samples and regular clinical data. The database and biobank will be available for studies of HP, and can be directly compared to the main PFBIO cohort, which has recruited patients with Idiopathic pulmonary Fibrosis (IPF) since 2016. Biomarkers will be assessed as diagnostic and prognostic. Further subtyping of HP, based on blood markers (including precipitins) will also be possible with the PFBIO-HP project.