The patient was a 76-year old man with pneumoconiosis. One year before admission, he was diagnosed with organizing pneumonia and started medication, including corticosteroids, because of intensified shadowing on chest X-ray. He was admitted to our hospital because of fever and cough that had recurred within a short period. Although hypersensitivity pneumonitis (HP) was strongly suspected, the causative antigen was not detected in interviews. On investigating his house, highly perfumed incense smoke was strongly suspected to be the antigen. An inhalation challenge test using the incense smoke was positive. Once the incense sticks, including the byproducts, had been removed from his house, he was discharged. Although corticosteroid therapy was tapered thereafter, the shadows on chest X-ray disappeared and there has been no recurrence.
This is the first case report of HP induced by incense smoke, but it may previously have been overlooked. Therefore, it is very important to visit and check the patient’s entire living environment when the antigen is not identified during the usual interviews.