A case of hypersensitivity pneumonitis caused by a humidifier: diagnosis and management in rural practice

Hypersensitivity Pneumonitis (HP) is an allergic interstitial lung disease that arises from type III and IV allergic reactions. During the COVID-19 outbreak, HP was established as having similar manifestations to COVID-19. In remote rural regions of Japan, where respiratory specialists are not readily accessible, HP is not always easy to differentiate, and establishing a definitive diagnosis can be challenging due to insufficient laboratory examinations. Herein, we present a case of a moderately definite diagnosis of acute non-fibrosing HP. The foundation of treatment included antigen avoidance, which necessitates a comprehensive analysis of the patient's medical history. In instances where anomalous chest imaging outcomes are observed, it is imperative to conduct a comprehensive review of the patient's medical history, and to consider the possibility of HP.