Elevated alveolar nitric oxide concentration after environmental challenge in hypersensitivity pneumonitis

We describe a 57-year-old male patient admitted to hospital with hypersensitivity pneumonitis (HP) that resolved without treatment. The total and alveolar nitric oxide (NO) concentrations were measured on initial admission and after re-exposure to his home environment. Following environmental exposure he became ill again, alveolar NO concentration was increased to the same level as on initial admission and impaired pulmonary function and radiologic abnormalities were found. It suggested a diagnosis of environmentally induced HP. The clinical value of measuring alveolar NO as an acute-phase reactant in HP is demonstrated in this patient.