Fact-sheet: Hypersensitivity pneumonitis
Updated on 09/17/2021 at 12:16 PM
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Definition
Hypersensitivity pneumonitis:
Multiple allergens: bird droppings (pigeons, doves, parakeets, canaries...), moldy hay (farmer's lung), fungal spores, ventilation systems...
Clinical features
Dry cough, dyspnea, and fever occurring rapidly after exposure
CT
Acute stage:
- Diffuse ground-glass opacities, bilateral patchy areas, or mosaic pattern.
- Ill-defined centrilobular micronodules ++
- Diffuse, bilateral, and symmetric involvement
Chronic stage:
- Interstitial fibrosis with reticular opacities, microcystic cavities, more rarely bronchiolectasis
- Apical predominance (in contrast to UIP and IPF)
- Large cysts possible (5-8 cm)
Rapid improvement upon allergen avoidance
