Which condition is caused by sensitization from intense prolonged exposure to inhaled organic antigens?

• A. Hypersensitivity pneumonitis
• B. Pulmonary hypertension
• C. Wegener Granulomatosis
• D. Goodpasture syndrome

Answer: (A)

Intense prolonged exposure to inhaled organic antigens sensitizes the immune system and triggers hypersensitivity pneumonitis, an immune-mediated lung disease. In this condition, repeated inhalation of organic dust—such as moldy hay, bird proteins, or contaminated humidifier dust—induces both antibody and T-cell–mediated responses in the lungs. This leads to alveolitis and interstitial inflammation, often with noncaseating granulomas, and can present acutely after exposure or chronically with fibrosis if exposure continues. The underlying mechanism involves immune reactions to inhaled antigens rather than autoimmune attack on the lungs or vasculitis. The other conditions listed are not driven by this kind of inhaled-antigen sensitization: one is a vascular/autoimmune disease not tied to organic exposure, another is an ANCA-associated vasculitis, and the last is antibody-mediated injury to basement membranes.