Study Objectives: This study reports a classic case of hypersensitivity pneumonitis (HP) with classic histologic changes in lung tissue and the research used to identify the causative antigens.
Design: A patient with clinical, radiographic, pulmonary function abnormalities and a lung biopsy consistent with HP had no identifiable antigen exposure.
Setting: Evaluation of the patient's activities provided no suggestion of antigen exposure. Her home was evaluated. It was found that her humidifier ran continually without being cleaned but water was added periodically.
Measurements: Serologic analysis demonstrated precipitating antibodies against her humidifier water and ten antigens in the hypersensitivity lung disease serologic panel.
Conclusion: Removal of the humidifier, cleaning of the house, and a course of prednisone resulted in the return of the patient to a normal state.