CTICasesNon-Fibrotic Hypersensitivity Pneumonitis
Imaging findings
Chest CT reveals a diffuse hyperattenuation pattern with prominent mosaic attenuation. Expiratory CT imaging clearly demonstrates extensive lobular air trapping throughout both lungs. There are no signs of underlying pulmonary fibrosis or architectural distortion. Pathologic evaluation from a surgical lung biopsy demonstrates an airway-centric inflammatory process with bronchiolar metaplasia extending away from the bronchioles (peribronchiolar metaplasia or lambertosis) alongside loose, poorly-formed interstitial granulomas and multinucleated giant cells.
Key takeaways
The combination of mosaic attenuation and lobular air trapping on expiratory CT in a patient with dyspnea is highly characteristic of non-fibrotic hypersensitivity pneumonitis. Pathologically, the disease is defined by peribronchiolar metaplasia, which represents bronchial epithelium extending beyond the airway lumen, and loose interstitial granulomas. While a multidisciplinary consensus can often establish the diagnosis of hypersensitivity pneumonitis using non-invasive clinical findings and bronchoalveolar lavage lymphocytosis, surgical biopsy provides definitive histopathologic confirmation when the triggering antigen remains unidentified.
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