male patient 45 yold, non-smoker, previous healtly. One year ago, abruptely manifest dispnoea, cough. A CT lung showed bilateral symmetric infiltrates, subpleural with pattern ground glass . The patient was treated with low doses of prednisone (25 mg os for 2 months). He recovered and the lung infiltrates disappeared . Another CT scan , one years after, showed again the same infiltrates with different pattern but the patient is asymptomatic.