High-resolution CT of Nontuberculous Mycobacteria Pulmonary Infection in Immunocompetent, Non-HIV-positive Patients

Purpose: The objective of this study was to demonstrate that nontuberculous mycobacteria (NTM) pulmonary infections are not so infrequent and that the diagnosis may be suggested on the basis of the high-resolution computed tomography (HRCT) pattern alone.

Materials And Methods: We retrospectively reviewed HRCT scans of 29 patients (9 men, 18 women; mean age 63 years, range 38-88 years) with positive culture from bronchial wash. Mycobacterium avium complex (MAC) was present in all (with the exception of one in whom the NTM was indistinct). In six patients, MAC was associated with M. chelonae, M. kansasii, M. fortuitum or M. xenopi. In one of these patients, MAC was associated with both M. fortuitum and M. chelonae. All patients had had nonspecific symptoms of pulmonary infection for a time ranging from 6 months to 12 years. Previous tuberculous infection was present in five patients (18.5%). Eleven patients had other pulmonary diseases (40.8%), and 12 had associated systemic diseases (44.4%).

Results: HRCT findings were apical fibrotic scarring (n=8; 29.6%), consolidations (n=16; 59.2%), single/multiple nodules >1 cm (n=8, multiple; 29.6%), cavitations (n=7; 25.9%), ground glass appearance (n=3; 11.1%), reticular/reticulonodular pattern (n=6; 22.2%), bronchiectasis (n=25; 92.5%), centrilobular nodules (tree in bud) (n=24; 88.8%), air trapping (n=8; 29.6%), lymphadenopathy >1 cm, also with calcification (n=13, 3 with calcification; 48.1%) and pleural effusion (n=2; 7.4%). In 3/7 patients with nodules >1 cm and with cavitations, the "feeding bronchus sign" (a patent bronchus running into a cavitation) was present. Lesions were in the upper lobes in 23 (85.1%), middle lobe/lingula in 25 (92.5%) and lower lobes in 18 (66.6%) patients. The findings were diffuse in 13 (48.1%) cases and patchy in 17 (62.9%).

Conclusions: HRCT findings are essential for the diagnosis of NTM pulmonary infection. The presence of bronchiectasis, cavitary nodules with feeding bronchus sign and tree-in-bud nodules in the middle lobe and lingula are suggestive of NTM infection, thus assisting the physician in the diagnostic workup of these patients.