Nodular distribution pattern on chest computed tomography (CT) in patients diagnosed with nontuberculous mycobacteria (NTM) infections

Background: This study evaluated the prevalence of spreading pathways in nontuberculous mycobacteria (NTM) pulmonary infections according to nodular distribution patterns seen on chest computed tomography (CT). Methods: This study included 63 patients diagnosed with NTM lung infections who underwent CT at our institution. A retrospective analysis of CT images focused on the presence and distribution of nodules, presence of intrathoracic lymphadenopathy and the predominant side of infection in the lungs. The findings were classified into five groups; centrilobular (bronchogenic spread), perilymphatic (lymphangitic spread), random (hematogenous spread), combined pattern and no nodules present. The groups were then compared according to other CT findings. Results: Among 51 (81%) patients identified with a nodular pattern on chest CT, 25 (39.8%) presented with centrilobular, 7 (11.1%) with perilymphatic, 6 (9.5%) with random and 13 (20.6%) with combined nodular patterns but located in different areas of the lungs. The right side of the lungs was predominant in 38 cases (60.3%). Intrathoracic lymphadenopathy was evident in 20 patients (31.7%). Significant differences in distributions of nodular patterns were seen in patients infected with Mycoplasma avium complex (MAC) associated with centrilobular pattern (p = 0.0019) and M. fortuitum associated with random pattern (p = 0.0004). Some of the findings were related to perilymphatic nodules between other isolated species of NTM (p = 0.0379). Conclusion: The results of this study showed a high proportion of perilymphatic nodules and right-sided predominance in the upper lobe, which, combined with intrathoracic lymphadenopathy is highly suggestive of the lymphangitic spread of lung NTM infections.