A 20-year-old college student presents to you with productive cough and fatigue for the last 7 months. He was in his usual state of health before this school year, but he tells you that since he moved into a new apartment with a new roommate, he has been intermittently ill. He also reports an unintentional weight loss of 15 pounds in a 3-month period and loss of appetite.
His past medical history is negative. His past surgical history is significant for tonsillectomy and adenoidectomy at 9 years of age. He is not taking any medications and has no known allergies to medications. He has seasonal allergies to mold and ragweed for which he uses over-the-counter antihistamines as needed. He does not smoke but his roommate is a smoker. His roommate has a pet parakeet.
On examination, he is a thin man in no distress. Lung auscultation reveals crackles and wheezing. His temperature is 99.8°F.
Chest x-ray reveals a nonspecific diffuse interstitial pattern. Computed tomography reveals ground-glass opacities in the lower lobes. Pulmonary function studies reveal reduced forced vital and total lung capacities, with the preservation of airflow.
Lung biopsy reveals the following hematoxylin and eosin stain at 40× magnification (see figure):
Which of the following is the most likely etiology of his symptoms?
This question appears in Med-Challenger FNP Exam Review with CME
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