Subacute / chronic dyspnea with antigen exposure, suspected hypersensitivity pneumonitis
Recommended: HRCT Chest (inspiratory + expiratory) is the preferred imaging study for subacute / chronic dyspnea with antigen exposure, suspected hypersensitivity pneumonitis. Antigens: birds, molds (farmer's lung), hot tubs, isocyanates.
Recommended study
HRCT Chest (inspiratory + expiratory)
Antigens: birds, molds (farmer's lung), hot tubs, isocyanates. Three phenotypes: non-fibrotic, fibrotic, mixed.
If the default doesn't apply
Diagnostic uncertainty
BAL + transbronchial biopsy ± SLB
No contrast
Watch-outs
Distinguish from IPF / NSIP
Fibrotic HP can mimic IPF on imaging; expiratory air-trapping favors HP. Antigen avoidance is essential management.
Pearls
- Classic triad: centrilobular ground-glass nodules + mosaic attenuation + air-trapping on expiratory imaging.
- Head-cheese sign: mixed ground-glass + air-trapping + normal lung.
- Antigen identification through detailed exposure history; serum precipitins variable.