Interstital lung disease due to contamination of forced air systems.

Eight patients had hypersensitivity pneumonitis due to contaminated home or office forced-air heating or air-conditioning systems. We studied their clinical and laboratory features, and the results indicated that this disease may occur as an acute or insidious form differing in type and intensity of respiratory and systemic symptoms. Thermophilic actinomycetes contaminatinf the forced air systems were identified as the sensitizing agents in most cases. Precipitating antibodies to the organisms could be shown in the serums of the patients and the antigen identified by immunofluorescent studies in the three lung biopsies examined by this method. Inhalation challenge studies with the cultured organism or other materials obtained from the forced air systems reproduced the clinical syndrome in the four patients tested. Avoidance of the contaminated system, and the use of corticosteroids in more severe cases,seems to be appropriate therapy for patients with this disease.