Objective: The objective of our study was to analyze the serial CT findings of patients with the nodular bronchiectatic form of Mycobacterium avium complex (MAC) pulmonary disease treated with antibiotic therapy.
Materials and methods: Between January 2005 and December 2009, MAC lung disease was diagnosed in 475 patients at a single tertiary referral hospital. Of the 475 patients, 339 had a CT pattern of disease consistent with the nodular bronchiectatic form. Among these 339 patients, 110 patients treated with a combination of antibiotics for 1 year were selected for this study. Two independent chest radiologists reviewed retrospectively the chest CT scans of 101 patients (M. avium disease [n = 57] and M. intracellulare disease [n = 44]) in whom serial CT scans had been obtained at the beginning of and at 12 months after standardized therapy. Each CT study was assessed for the presence and extent of lung parenchymal abnormalities (maximum score, 30).
Results: After 12 months of antibiotic therapy, 84 patients (83%) had a decrease in the overall CT score, three (3%) had an increase, and 14 (14%) had no change in disease extent. The decrease in total CT score was statistically significant (overall score difference, 2.54; p < 0.0001). Cellular bronchiolitis showed the largest decrease in extent (difference in mean pre and posttreatment scores, -1.02, -1.07, and -0.94 for MAC, M. avium, and M. intracellulare diseases, respectively). Before treatment, patients with M. intracellulare disease showed more extensive disease than patients with M. avium disease (total CT score, 13.31 vs 11.10; p = 0.025).
Conclusion: In the nodular bronchiectatic form of MAC pulmonary disease, lung parenchymal abnormalities show a significant decrease in extent on CT after antibiotic treatment and the decrease is mainly related to the improvement of cellular bronchiolitis.