A case of hypersensitivity pneumonitis showing acute respiratory distress syndrome due to exposure to dust containing diphenylmethane diisocyanate

: The patient was a 61-year-old man who reported coughing and fever that occurred immediately after the work of breaking up a large refrigerator containing diphenylmethane diisocyanate (MDI). He was brought to our medical center with respiratory distress ten days after onset. Acute respiratory distress syndrome was diagnosed on the basis of a P/F oxygen ratio of less than 200 and chest CT findings of extended consolidation in both lung fields. He was intubated and ventilated mechanically. Steroid pulse therapy was started because of an elevated lymphocyte count found through bronchoalveolar lavage (BAL). After that, arterial blood gas and chest radiography findings improved gradually, and high-resolution chest findings on the 4th day of hospitalization showed centrilobular and uncleared shadows of marginated acini in both lung fields. The patient was extubated ten days after admission, the steroid therapy was withdrawn, and he was discharged from the intensive care unit on the 22nd day of hospitalization. Transbronchial lung biopsy on admission revealed alveolitis, Masson bodies and activated macrophages in the air spaces. The dismantled refrigerator was known to contain MDI, and because of the IgE and the IgG to MDI present in the serum, and of the IgG to MDI in the BAL fluid, we diagnosed hypersensitivity pneumonitis with acute respiratory distress syndrome due to exposure to dust containing MDI. There are many reports of painters with hypersensitivity pneumonitis following exposure to isocyanates, but care should be taken to avoid the possibility of acute respiratory distress syndrome arising because of the inhalation of dust mixed with isocyanates.