A 17-year-old man was admitted with a 5-month history of intermittent dyspnea onexertion, 10kg weight loss, cough, sputa and fever. He did not smoke, had no apparent underlying pulmonary disease, and was not immunocompromised. Mycobacteriumfortuitum was cultured from sputa at admission. Chest radiograph showed many thinwalled cavities and infiltration in the bilateral middle and upper fields. Chest CT detected multiple cystic lesions that were not revealed in conventional X-ray. It was suggested that the formation of the cystic lesions was one of the predisposing factor of Mycobacterium fortuitum pulmonary infection in this patient. The pneumonic change improved after sixmonth treatment using isoniazid, rifampicin and streptmycin, despite in vitro resistance of the bacilli to all of these drugs.
