器質化肺炎像を呈した過敏性肺炎疑いの1例

A Case of Highly Suspected Hypersensitivity Pneumonia Presenting Pathologically as Organizing Pneumonia Pattern

要旨　患者は67歳，男性．20年以上同じマンションに住み，加湿器・24時間循環式風呂使用．入院約2週間前より感冒様症状あり，胸部CT上両側上肺野中心の斑状陰影を認め，入院．抗菌薬投与で改善し，第8病日に退院した．翌日より発熱，呼吸苦出現し，退院5日後に再入院したが入院後速やかに改善した．試験外泊後に炎症所見の増悪，胸部CT上，肺野末梢側有意にびまん性スリガラス様陰影を認めたことから，過敏性肺炎を疑い，胸腔鏡下肺生検を施行した．病理組織検査で器質化肺炎像を認め，第23病日からステロイドの投与を開始した．自宅の全面リフォーム後，退院し，ステロイドを漸減・中止したが，再燃なく経過中である．本例は臨床経過や画像上，急性過敏性肺炎が強く疑われるも，病理組織像は特徴的な肉芽腫を認めず，器質化肺炎像を認めた．過敏性肺炎の経過と病理組織像を考えるうえで貴重な症例と考えられた．

　A 67-year-old man, who lived in an apartment room for more than 20 years and regularly used the humidifier and private bath keeping hot water for one day, was admitted to our hospital because of fever, cough and dyspnea. Chest X-ray and CT on admission revealed diffuse infiltration of the bilateral upper lung fields. His symptoms and infiltrative shadows on chest X-ray were quickly improved by the administration of antibiotics, and he was discharged from hospital 8 days after admission. One day after discharge, fever and dyspnea recurred, and he was re-admitted to hospital. Chest X-ray and CT demonstrated diffuse ground glass infiltration of the bilateral lung fields, which quickly improved after re-admission. After a trial of home-stay for several days, body temperature, white blood cell count and serum C-reactive protein level were elevated again. We suspected hypersensitivity pneumonea(HP), and surgical lung biopsy with thoracoscopy was performed. The pathological specimen showed organizing pneumonia, but no typical nonnecrotizing granulomas. Administration of corticosteroid was started and his symptoms and radiologic findings were improved. He was discharged after drastic modification of his home, and his suspected HP has not recurred, in spite of tapering and stopping the corticosteroid. This case was highly suspected to be acute hypersensitivity pneumonia. However, the histopathological examination demonstrated organizing pneumonia pattern without typical granulomas.