Hypersensitivity Pneumonitis: Challenges of a Complex Disease

Figure 1

Imaging patterns in HP. (a) Axial section of chest high-resolution computer tomography (HRCT) showing ill-defined centrilobular nodules (white asterisk) and areas of air-trapping (arrows) suggesting small airway involvement. (b) Ground-glass opacities and mosaic attenuation (ground glass alternating with air-trapping (arrows)) suggestive of predominant interstitial infiltration. (c) The “three density sign” comprised of lung lobules with normal density (white asterisk), lobules with ground-glass attenuation (arrowheads), and lobules with decreased density due to air-trapping (arrows). (d) Fibrotic HP presented by areas of ground glass accompanied by traction bronchiectasis (black arrow) and honeycombing (white arrow).

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