Unilateral Lung Involvement of Nodular Bronchiectatic Mycobacterium Avium Complex Pulmonary Diseases: Proportion and Evolution on Serial CT Studies

OBJECTIVE. We aimed to explore proportion, involved organisms, and serial CT features of nodular bronchiectatic (NB) Mycobacterium avium complex (MAC) pulmonary diseases that manifested as unilateral lung disease. MATERIALS AND METHODS. We retrospectively identified 674 patients with NB MAC pulmonary disease (PD) who underwent serial CT studies from January 2005 through December 2012. We selected patients with unilateral lung involvement as its initial manifestation. Retrospective analyses on serial CT findings in terms of presence and extent of lung abnormalities were performed. The organism identified (M. avium vs M. intracellulare) and treatment status were reviewed. To find the factors related to progression to involve both lungs, Cox regression analysis was performed. RESULTS. Unilateral MAC PD on initial CT was found in 47 patients (7%). Among them, 10 (21%) showed disease progression on follow-up CT to involve both lungs (mean evolving time, 1536 days). All 10 of these cases initially involved the right lung. Of these 10 patients, eight needed antibiotic treatment because of deteriorating imaging findings (4/8, 50%) or worsening symptoms (4/8, 50%). Initial total CT score (hazard ratio [HR], 1.414; 95% CI, 1.092-1.831; p < 0.01) and age (HR, 1.076; 95% CI, 1.004-1.154; p < 0.05) were related factors for disease progression in simple Cox regression test. CONCLUSION. Unilateral lung involvement of NB MAC PD is an occasional (7%) manifestation, and disease progressed in approximately 20% of patients in our study to involve both lungs. The imaging factor most related to disease progression appears to disease extent on initial CT.