[A case of solitary pulmonary nodule caused by Mycobacterium avium]

A 56-year-old male without respiratory symptoms, past history nor familial history, was admitted to our hospital because of pulmonary solitary nodule on the chest radiograph. Computed tomograph showed a smooth surface nodule in the left lower lobe (segment 8). Bronchofiberscopy could not give any specific histological findings nor bacteriological findings, therefore the patient underwent partial pulmonary resection by videoassisted thoracoscopic surgery. Pathology of the resected specimen revealed epithelioid cell granuloma with giant cells but not any acid-fast bacilli. He was treated with rifampicin and isoniazid for "tuberculoma". After three weeks, thirty colonies grew on an Ogawa's egg medium, which were identified as Mycobacterium avium by PCR. There are few reports about the solitary pulmonary nodule due to M. avium-intracellurale complex infection, however, it is supposed that there are many "tuberculoma's" without bacteriological differentiation between tuberculosis and nontuberculous mycobacterial infection. It is difficult to diagnose a solitary pulmonary nodule caused by nontuberculous mycobacterial infection with bronchofiberscopy, and the location of the lesion is usually subpleural, therefore it is thought that videoassisted thoracoscopic surgery is valied for the diagnosis of solitary pulmonary nodule due to nontuberculous mycobacterium.