Reactive airways dysfunction syndrome induced by exposure to a mixture containing isocyanate: functional and histopathologic behaviour

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Abstract
A 31-year-old machinist experienced acute symptoms of rhinoconjunctivitis, coughing, shortness of breath, and wheezing after sudden exposure to fumes containing isocyanates and solvents. Lung function tests carried out 11 days after the event showed reduced flow rates. Forty days after the acute inhalational injury, expiratory flows improved, and the PC20 was 0.8 mg/ml, showing moderate bronchial hyperresponsiveness. Six days later, the subject underwent bronchoscopy. Bronchial biopsies showed a marked loss of epithelial cells, severe subepithelial oedema, and inflammatory cells infiltrate (mainly lymphocytes). The subject was given inhaled steroids. The PC20 was back to normal 42 days later. Bronchial biopsies then showed incomplete regeneration of the epithelial layer with few ciliated cells and persistence of inflammation (lymphocyte infiltrate) in epithelia and connective tissue. We conclude that irritant exposure to a mixture of isocyanates and solvents can cause occupational asthma without a latency period, i.e., reactive airways dysfunction syndrome.