[Two cases of M. avium complex infection presenting as solitary pulmonary nodule]

Case 1 was a 75-year-old woman. Her chest X-ray showed a 3 cm solitary nodule in the right S4, and biopsy obtained by fiberoptic bronchoscopy revealed epithelioid cell granuloma. Four weeks later, Mycobacterium avium complex (MAC) was detected on culture of the bronchial lavage fluid. She was treated with INH, RFP and EB for 12 months and recovered with no relapse. Case 2 was a 75-year-old man with mild diabetes mellitus and hypertension. Chest X-ray showed a 4 cm solitary nodule in the right S9. Percutaneous pulmonary aspiration revealed numerous acid-fast bacilli on smear, and he was treated with INH, RFP and EB. Culture proved M. avium complex. The patient was unable to continue his medications because of gastrointestinal side effects, so right lower lobectomy was performed. Cases of M. avium complex infection presenting as solitary pulmonary nodule are very rare. We found only 12 reported cases in Japan and in other countries. The most usual site of cavitary lesions in M. avium complex infections is both upper lobes, in contrast to the relatively even distribution of solitary pulmonary nodules of the 14 cases (12 reported cases and our 2 cases).