[A mild case of acute eosinophilic pneumonia]

We encountered a mild case of acute eosinophilic pneumonia in a 24-year-old man who developed symptoms once he started smoking. Bronchoalveolar lavage revealed eosinophilia. Chest computed tomography revealed a small amount of bilateral pleural effusion and multicentric panacinar shadows with peripheral ground-glass opacities. During the clinical course, the patient suffered only cough and fever, which subsided in 13 days without the administration of steroids. Although the clinical course in this case resembled that of simple pulmonary eosinophilia, we diagnosed it as a mild case of acute eosinophilic pneumonia because pleural effusion rarely accompanies simple pulmonary eosinophilia, symptoms developed when the patient began smoking, and interstitial involvement was suggested by bilateral effusion and ground-glass opacity. We look forward to the establishment of the disease concept of acute eosinophilic pneumonia, including mild cases, and a classification system for eosinophilic lung diseases, including acute eosinophilic pneumonia.