Diffusely distributed centrilobular micronodules and branching opacities as the main chest computed tomography manifestations in a patient with humidifier lung.

We report a 60-year-old man with humidifier lung showing diffusely distributed centrilobular micronodules and branching opacities on chest computed tomography (CT). Fever and dyspnea occurred 2 months after using an ultrasonic humidifier. KL-6 and SP-D were within normal ranges. Bronchoalveolar lavage showed elevated lymphocytes (53 %) and histological findings of transbronchial lung biopsy demonstrated organizing pneumonia. His condition improved after cessation of the humidifier. A provocation test exhibited a positive response to the humidifier. Humidifier lung should be considered as a differential diagnosis in patients with these CT findings. Detailed clinical, pathological and microbiological examinations are needed to exclude other diseases.