CTICasesRapidly Progressive Hypersensitivity Pneumonitis
Imaging findings
A 53-year-old former smoker had a baseline CT with paraseptal emphysema and mild upper-lung-predominant asymmetric fibrosis with mosaic attenuation and air trapping. About 16 to 18 months later he developed large subpleural cystic spaces, bullae/blebs, honeycombing, and pneumothoraces tracking medially into the mediastinum. He lives with a parrot and a dove; surgical biopsy showed a cellular interstitial pneumonia exceeding smoking-related change, numerous giant cells and rare poorly formed peribronchovascular granulomata, organizing pneumonia, and constrictive bronchiolitis, favoring subacute-to-early chronic hypersensitivity pneumonitis.
Key takeaways
Hypersensitivity pneumonitis (here with bird exposure) can rarely show striking cystic change and unusually rapid progression, confounded by coexisting paraseptal emphysema and smoking-related change. Recognizing HP features (heterogeneity, mosaic attenuation, mild upper-lung fibrosis) against a smoking background is difficult, and the histology showing chronic inflammation beyond smoking with poorly formed peribronchiolar granulomas supports the diagnosis despite the atypical rapid, cystic evolution.
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