[Hypersensitivity pneumonitis caused by a home humidifier].

A 33-year-old man was admitted complaining of a fever, dyspnea, and a dry cough almost every night since December of 1992. He had been using an ultrasonic humidifier at home. The chest CT scan and roentgenogram showed bilateral reticulonodular shadows. After admission, the symptoms resolved spontaneously. These findings were suggestive of hypersensitivity pneumonitis. After analysis of fluid obtained by bronchoalveolar lavage and of a specimen obtained by transbronchial biopsy, "humidifier lung" was diagnosed. Ten species of microorganisms were isolated from the water left in the patient's humidifier. On precipitation and complement fixation tests of the patients serum, the results were positive for three of those microorganisms: Flavobacterium multivorum, Yersinia pseudotuberculosis, and Aureobacterium liquefaciens. The titer on the complement fixation test increased immediately after a provocation test. The laboratory results suggest that at least one of these three microorganisms was the causative antigen in this case.