[A case of hypersensitivity pneumonitis probably caused by a humidifier in winter]

A 64-year-old man was admitted complaining of cough, hemoptysis, dyspnea, and fever. His chest X-ray film on admission showed reticulo-granular shadows in both lung fields. Ausculation of his chest revealed fine crackles in both lower zones. After admission, he was treated with antibiotics, but his chest-radiographic appearance worsened temporarily, and sputum cytology results were repeatedly positive. Diagnosis was difficult. Differential cell count of the bronchoalveolar lavage fluid showed lymphocytosis, with a high CD 4/8 ratio. Transbronchial lung biopsy specimens revealed Masson bodies and alveolitis. With antibiotic therapy alone, his condition improved, and he was discharged. Five and a half hours later, his symptoms worsened and he was readmitted. His chest X-ray film on the second admission was almost the same as that on the first admission. His symptoms became less severe, and his condition improved without treatment. Hypersensitivity pneumonitis was diagnosed. Because the onset was in February, this was not considered to be a case of so-called summer type hypersensitivity pneumonitis a provocation test was done with water from the humidifier he had been using at home. The white blood cell count increased and PaO2 decreased significantly, so the result of the provocation test was thought to be positive. Therefore, so-called humidifier lung was strongly suspected. The results of sputum cytology on the first admission were probably falsely positive.