CTICasesChronic Hypersensitivity Pneumonitis (Progression with Loss of Air Trapping)
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Imaging findings
Initial CT (2007) showed ground glass opacities, mosaic attenuation, and peripheral reticular abnormalities, with confirmed air trapping on expiratory images. Subsequent CT (2014) demonstrated worsening fibrosis with increased reticulation and traction bronchiectasis, particularly in the upper lung zones. Notably, the previously evident air trapping was significantly reduced or absent on later expiratory images.
Key takeaways
While air trapping is a characteristic finding in subacute hypersensitivity pneumonitis, it can become less apparent or even resolve as the disease progresses to a chronic fibrotic stage. Therefore, the absence of air trapping on expiratory imaging in a patient with fibrotic lung disease and a compatible history should not necessarily exclude the diagnosis of chronic hypersensitivity pneumonitis. Fibrosis in HP can also appear upper lung predominant.
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