Longitudinal changes in radiographic features of pulmonary Mycobacterium avium complex diseases

Background: The radiographic features of Mycobacterium avium complex pulmonary disease (MAC-PD), a major component of nontuberculous mycobacteria, consist of a variety of lesions; however, the responsiveness of each type of radiographic factor to treatment is unclear. Thus, we evaluated the longitudinal changes of each factor in serial computed tomography (CT) images using a mixed-effects model, and investigated the radiographic transition in patients with MAC-PD whose progress could be followed.Methods: In this retrospective study, eighty-four patients diagnosed with MAC-PD and with yearly CT records were recruited after a review of 328 medical records with culture-positive MAC in respiratory specimens. The study participants were divided into two groups: treatment (n = 43) and no-treatment (n = 41) groups. Radiographic images were scored using the nodule (N), infiltration (I), cavity (C), ectasis (E) scoring system. Longitudinal changes in each radiographic lesion factor were analyzed using a mixed-effects model in treated and untreated patients.Results: All factors tended to progress without treatment, and significant longitudinal changes were observed in the N, I, and E factors (N: p = 0.010, I: p = 0.004, E: p < 0.001). Although treatment tended to improve N and I in radiographic images (N: p = 0.006, I: p = 0.203), cavities and ectasis progressed, regardless of treatment (C: p = 0.057 and E: p = 0.033).Conclusion: Radiographic changes of MAC-PD can be categorized into reversible (nodules and infiltrations) and irreversible (cavities and ectasis) lesions. Early treatment may prevent the accumulation of irreversible factors.