Restrictive Lung Disease USMLE Step 1 Practice Question

A 52-year-old man with a 10-year history of raising pigeons and parrots presents to the emergency department with acute onset of fever (38.9°C), chills, dyspnea, and nonproductive cough that began 4 hours after cleaning bird cages. He reports no recent travel, sick contacts, or respiratory symptoms prior to today. On examination: HR 108/min, RR 24/min, BP 128/82 mmHg, SpO2 88% on room air. Lungs have fine crackles bilaterally. Chest X-ray shows diffuse bilateral ground-glass opacities with relative sparing of lung apices. Pulmonary function tests demonstrate FVC 68% predicted, FEV1 75% predicted, and normal FEV1/FVC ratio. CBC shows mild leukocytosis (11,200/μL). Which of the following is the most likely diagnosis?