background: the retrospective investigation of a fatal sporadic legionnaires' disease identified an unknown case of occupational hypersensitivity pneumonitis in a swine breeder. methods: chest high-resolution computed tomography, bronchoalveolar lavage, lung biopsy, arterial gasometry, pulmonary function tests and autopsy were performed. it was studied the presence of legionella by serology and risk water samples were analyzed to identify the legionella's source. results: hp and legionella pneumophila pneumonia diagnostics were confirmed. lung fibrosis, a restrictive functional pattern, decreased diffusion, hypoxemia and bronchoalveolar lavage lymphocytosis were evidenced. legionella′s source was detected in a shower and a positive serology in the patient. autopsy verified pulmonary fibrosis and the septic shock leaded to legionella causing the death. conclusions: chronic cough and pulmonary infiltrates in a farmer should suspect the presence of hypersensitivity pneumonitis. later diagnosis carries a worse prognosis, the offending antigens exposure can't be avoided and fibrotic stage enhanced opportunity infection disease.