Hypersensitivity pneumonitis CT

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Acute hypersensitivity pneumonitis

• Chest radiographs in affected patients may be normal; thin-section CT can be helpful in these patients for showing characteristic centrilobular ground glass or nodular opacities.
• When abnormal, chest radiographs typically show focal or diffuse heterogeneous or homogeneous opacities.

Subacute hypersensitivity pneumonitis

• Patients with subacute disease usually have a more indolent clinical presentation. Nodular opacities are a characteristic feature on chest radiographs and CT. Centrilobular ground-glass or nodular opacities on CT suggest the diagnosis.
• Head cheese sign

Chronic hypersensitivity pneumonitis

• Chronic disease typically manifests with upper lung zone fibrosis. Characteristic distribution and presence of centrilobular nodules on CT help distinguish chronic hypersensitivity pneumonitis from idiopathic pulmonary fibrosis.

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