Review Question - QID 110015

A 67-year-old man presents to his primary care provider with difficulty breathing. He reports a 7-month history of progressively worsening exertional dyspnea. He has also developed a mild nonproductive cough. His past medical history is notable for major depressive disorder, hypertension, and diabetes mellitus. He takes fluoxetine, enalapril, metformin, and glyburide. He has a 15-pack-year smoking history and quit 20 years ago. He drinks a 6-pack of beer a week. His temperature is 99.1°F (37.3°C), blood pressure is 140/80 mmHg, pulse is 82/min, and respirations are 22/min. On exam, fine bibasilar inspiratory crackles are noted along with digital clubbing. Antinuclear antibody and rheumatoid factor titers are low. Results of a high-resolution computed tomography (CT) scan are shown in Figure A. Which of the following is the underlying cause of this patient's condition?