Chronic exposure of ______ leads to progressive respiratory fibrosis/failure.

• A. Asthma
• B. Hypersensitivity pneumonitis
• C. COPD
• D. Pneumonia

Answer: (B)

Chronic exposure to inhaled organic antigens in hypersensitivity pneumonitis triggers ongoing immune-mediated inflammation of the alveolar-interstitial tissue. With continued exposure, this inflammation can progress to fibrosis, causing a restrictive lung pattern and eventual respiratory failure. This differs from asthma, which is driven by reversible airway hyperreactivity and obstruction; COPD, which involves chronic airflow limitation from smoking-related changes; and pneumonia, an acute infection with alveolar consolidation rather than progressive fibrotic remodeling. In chronic hypersensitivity pneumonitis, fibrotic changes can lead to reduced lung volumes, decreased diffusing capacity, and even honeycombing on imaging as fibrosis advances.