Humidifier-Related Lung Injury Leading to Hypersensitivity Pneumonitis: A Case Report

Humidifier lung is a subtype of hypersensitivity pneumonitis (HP) triggered by repeated exposure to an antigen. The mainstay of therapy is antigen avoidance. A Caucasian male in his 30s presented with a six-month history of progressively worsening dyspnea and cough. On presentation, he was hypoxic on room air. Laboratory work was significant for a leukocytosis and a CT angiogram of the chest demonstrated diffuse ill-defined ground-glass opacities in both lungs. The patient was admitted for community-acquired pneumonia, but his symptoms worsened, so additional infectious and rheumatological work-up was obtained. History revealed the patient used a home humidifier daily for the past year. Cultures obtained from the humidifier grew Staphylococcus saprophyticus. Lung biopsy demonstrated diffuse lymphoplasmacytic infiltrates and poorly formed granulomas consistent with HP. The humidifier was removed from the individual's home, and he was treated with systemic steroids, with complete resolution of his symptoms. Obtaining a detailed history plays a pivotal role in diagnosing HP.