Hypersensitivity pneumonitis due to high-dose colistin aerosol therapy.

We report a case of hypersensitivity pneumonitis, possibly due to aerosolized colistin therapy for severe multi-resistant Gram-negative pneumonia. Microbiological eradication was achieved with colistin therapy, which was stopped after 12 days in view of rising eosinophilia and possible lung fibrosis. The eosinophil count started to normalize 3 days after stopping colistin therapy and the patient was eventually weaned to minimal ventilatory support.