Trichosporon asahiiの血清抗体が陽性であった冬期発症加湿器肺の1例

A Case of Winter Onset Humidifier Lung Sensitized to Trichosporon asahii

要旨　症例は49歳男性．2月より2カ月続く抗菌薬抵抗性の発熱，咳嗽を主訴に来院した．胸部CTにて小葉中心性粒状影をびまん性に認め，気管支肺胞洗浄液ではリンパ球優位(52%)の細胞数増多を認め，CD4/CD8は0.6と低下していた．入院のみで症状・検査所見は改善し，加湿器を使用した自宅外泊試験陽性で，加湿器廃棄後は症状の再燃なく経過した．Trichosporon asahiiの血清抗体(ELISA法)が陽性であったが，加湿器水の培養では検出されなかった．本症例の原因抗原は明らかでないものの，夏型過敏性肺炎を引き起こすT. asahiiに感作されており，加湿器を介した冬期発症夏型過敏性肺炎の可能性が示唆される稀な1例と考えられた．

　A 49 year-old man was admitted to our hospital in April because of antibiotics-resistant fever and cough, which continued since February. The chest computed tomography showed diffuse small nodular shadows in bilateral lung fields. In the bronchoalveolar lavage fluid, total cell count increased with lymphocyte predominance(52%), and decreased CD4/CD8 ratio(0.6). After admission, symptoms and laboratory findings improved rapidly. The environmental challenge test was positive only when the humidifier was on, therefore, the diagnosis of humidifier lung was made. The patient's symptoms did not recur after the humidifier was discarded. The serum antibody to T. asahii was positive, however, the culture of water in the humidifier was negative for T. asahii. Although the responsible antigen was not clarified, the patient was sensitized to T. asahii, which suggests that this might be a rare case of winter onset summer-type hypersensitivity pneumonitis caused by humidifier.