Hypersensitivity Pneumonitis
Extrinsic allergic alveolitis - to inhaled organic small particles.
Recent guidelines:
CHEST: https://journal.chestnet.org/article/S0012-3692(21)00686-3/fulltext
ATS: https://www.atsjournals.org/doi/10.1164/rccm.202005-2032ST
ARUP's panel and what the significance of each result is:
Nonfibrotic:
Fibrotic:
Diagnostic algorithm (From ATS)
40% BAL lymphocytosis is strongly associated.
Treatment:
- Antigen removal (worse prognosis if no antigen is identified - Noguieria et al Pulmonology 2019)
- Steroids, but weak evidence base (RCT of 36 resulted in improvement in DLCo and FVC at 1 month but no difference at 5 years; matched cohort of 144 showed slower fibrosis progression on CT - esp early fibrosis)
- AZA, MMF - need to exclude IPF (increased mortality). Less side effects than long-term steroids.
- ? Nintedanib - INBUILD study, progressive fibrosis including 26.1% who had chronic HP