Four cases of pulmonary Mycobacterium avium intracellulare complex presenting as a solitary pulmonary nodule and a review of other cases in Japan

OBJECTIVE: To evaluate clinical findings of patients with a solitary pulmonary nodule in Japan caused by pulmonary Mycobacterium avium complex (MAC) disease. METHODS: The authors investigated the clinical features of 12 patients diagnosed as having pulmonary MAC disease who had presented with a solitary pulmonary nodule. RESULTS: The causative microorganisms were M. avium in seven patients, Mycobacterium intracellulare in two and MAC in three. The diagnostic methods were bronchoscopic biopsy or percutaneous lung biopsy in three patients and surgical operations in the remaining nine. Eleven patients had a complete surgical resection of the nodule and antituberculous drugs were administered to eight. On X-ray, there was an absence of calcification, satellite lesions, cavities, or bronchoectasis that are often thought to be characteristic of pulmonary mycobacterial disease. Differentiation from lung cancer was thought necessary in five patients. There was no microbiological or radiological relapse in those who underwent complete surgical resection. CONCLUSIONS: Because treatment is often poorly effective for patients with pulmonary non-tuberculous mycobacterial disease, it is important to identify the causative microorganisms by performing a culture examination of resected lung tissue especially if there is a solitary pulmonary nodule.