American Board of Internal Medicine (ABIM) Certification Practice Exam

What imaging findings are associated with acute hypersensitivity pneumonitis?

1. Upper lobe consolidation

2. Bilateral hazy opacities

3. Lower lobe emphysema

4. Bronchial wall thickening

The correct answer is: Bilateral hazy opacities

Acute hypersensitivity pneumonitis, also known as extrinsic allergic alveolitis, typically presents with imaging findings that reflect the inflammatory process occurring in the lungs as a response to inhaled antigens. In the case of acute disease, the most characteristic finding is the presence of bilateral hazy opacities, which is indicative of ground-glass opacities on imaging studies such as chest X-rays or CT scans. These hazy opacities represent areas of inflammation and interstitial edema in the alveolar spaces and can involve the lung peripheries, contributing to the diffuse appearance. This pattern is consistent with the acute inflammatory response in the lungs, where the alveoli become infiltrated with inflammatory cells due to the hypersensitivity reaction to the offending allergen. The other findings mentioned do not represent the typical imaging characteristics seen in acute hypersensitivity pneumonitis. For example, upper lobe consolidation is more commonly associated with conditions like tuberculosis or other infections rather than allergic reactions. Lower lobe emphysema is typically related to chronic obstructive pulmonary disease and does not match the acute presentation of hypersensitivity pneumonitis. Finally, bronchial wall thickening can occur in various chronic pulmonary conditions, including asthma, but is not a hallmark of