Review Question - QID 109873

A 68-year-old male with a history of chronic myelogenous leukemia presents to his oncologist complaining of shortness of breath. He reports developing progressively worsening dyspnea and a dry cough over the past 2 weeks. His past medical history is also notable for hypertension and gout. He takes imatinib, lisinopril, and allopurinol. He has a 40 pack-year smoking history and drinks 2-3 beers per day. He used to work in a foundry and is now a rancher working with sheep and goats. His temperature is 98.6°F (37°C), blood pressure is 135/75 mmHg, pulse is 90/min, and respirations are 22/min. On examination, he has slightly increased work of breathing and diffuse rales in the bilateral upper and lower lung fields. A chest radiograph demonstrates non-specific alveolar opacities. Endoscopic biopsy of the lung is performed with results shown in Figure A. This patient’s condition is most likely caused by which of the following?