Mycobacterium avium complex(MAC) is the most common respiratory pathogen in nontuberculous mycobacterial pulmonary disease. This study described the clinical characteristics of the patients with pulmonary disease caused by MAC.

The clinical characteristics of 24 patients with pulmonary disease caused by the MAC, who fulfilled the 1997 American Thoracic Society diagnostic criteria for nontuberculous mycobacterial pulmonary disease, were retrospectively analyzed.

Fourteen patients(58%) were male and the median age at diagnosis was 61 years(range 46-75). Of the 24 patients, 16(67%) had a M. intracellulare infection, 7(29%) had a M. avium infection and one patient was not identified. Coughing(92%) and sputum(88%) were most frequently observed symptoms. The sputum smear for acid-fast bacilli was positive in 17(71%) patients. Fourteen(58%) patients had the upper lobe cavitary form and 10(42%) patients had the nodular bronchiectatic form. In a comparison between the patients with the upper lobe cavitary form and those with the nodular bronchiectatic form, significant differences were found according to sex(male 86% vs. 20%, p=0.003), smoking history(79% vs. 10%, p=0.008), the presence of an underlying disease(64% vs. 20%, p=0.036), the pulmonary function(% forced vital capacity, median 71% vs. 88%, p=0.022; % forced expiratory volume in one second, median 69% vs. 89%, p=0.051) and bilateral disease at chest radiography(29% vs. 90%, p=0.005). The time from the onset of symptoms to diagnosis was longer in those with the nodular bronchiectatic form(median 72 months, range 8-132) than those with the upper lobe cavitary form(median 22 months, range 6-60)

MAC pulmonary disease occurs in two distinct populations with two distinct clinical presentations. For a correct diagnosis of MAC pulmonary disease, knowledge of the diverse clinical and radiological findings is essential.