ABSTRACT
A 22-year-old man was admitted to our hospital because of high fever and shortness of breath. A chest CT showed centrilobular nodules and ground-glass attenuation in both lungs. Transbronchial lung biopsy specimens showed alveolitis including the infiltration of mononuclear cells and granulomas. He responded to treatment, but upon returning home the radiological findings and clinical symptoms reappeared. We focused on a dehumidifier because it had been used continuously in his room. Thermoactinomyces vulgaris presented in the air filter of the dehumidifier. The test of precipitation in response to Thermoactinomyces vulgaris was positive. The condition inside the dehumidifier of a high temperature and high humidity were suitable for the proliferation of Thermoactinomyces vulgaris. We diagnosed hypersensitity pneumonitis due to a dehumidifier contaminated by Thermoactinomyces vulgaris.
