Diphenylmethane diisocyanate hypersensitivity pneumonitis: A serologie evaluation

We describe the clinical and immunologic evaluation of a steel plant maintenance supervisor who had clinical symptoms consistent with hypersensitivity pneumonitis. No antigen was obvious but after a thorough occupational history and review of the industrial hygiene data, the most likely antigen appeared to be diphenylmethane diisocyanate. Precipitating antibodies were not detected in the worker’s serum; however, significant antibody levels of IgG specifie for diphenylmethane diisocyan-ate-human serum albumin were detected by other immunoas-says. This case highlights the importance of a thorough occupational history and an aggressive laboratory immunologie evaluation in identifying the offending agent in a worker with hypersensitivity pneumonitis. Hypersensitivity pneumonitis due to an inhaled reactive chemical may be present without precipitins demonstrated in vitro due to the nature of the haptenized chemical protein conjugate or the concentration of IgG antibody.