Pulmonary Disease Due to Nontuberculous Mycobacteria: Current State and New Insights

Abstract

Since pulmonary nontuberculous mycobacteria (PNTM) lung disease was last reviewed in CHEST in 2008, new information has emerged spanning multiple domains, including epidemiology, transmission and pathogenesis, clinical presentation, diagnosis, and treatment. The overall prevalence of PNTM is increasing, and in the United States, areas of highest prevalence are clustered in distinct geographic locations with common environmental and socioeconomic factors. Although the accepted paradigm for transmission continues to be inhalation from the environment, provocative reports suggest that person-to-person transmission may occur. A panoply of host factors have been investigated in an effort to elucidate why infection from this bacteria develops in ostensibly immunocompetent patients, and there has been clarification that immunocompetent patients exhibit different histopathology from immunocompromised patients with nontuberculous mycobacteria infection. It is now evident that Mycobacterium abscessus, an increasingly prevalent cause of PNTM lung disease, can be classified into three separate subspecies with differing genetic susceptibility or resistance to macrolides. Recent publications also raise the possibility of improved control of PNTM through enhanced adherence to current treatment guidelines as well as new approaches to treatment and even prevention. These and other recent developments and insights that may inform our approach to PNTM lung disease are reviewed and discussed.

Figure 1 –

Chest CT image of a 70-y-old woman with a tall, lean body habitus; mitral valve prolapse; and a single CFTR gene mutation (G551D). She has an intermediate sweat chloride test result and presented with a chronic debilitating cough. Sputum cultures were positive for Mycobacterium avium-intracellulare complex. The CT image demonstrates multiple nodules bilaterally with patchy bronchiectatic changes and tree-in-bud abnormalities (arrow).

Figure 2 –

Chest CT image of a 65-y-old woman who presented with productive cough, weight loss, and fatigue. Sputum was acid-fast bacilli smear positive and culture positive for Mycobacterium abscessus. This CT image shows a more advanced stage of bilateral nodular bronchiectasis than seen in the patient presented in Figure 1.

Figure 3 –

Chest CT coronal view image of an 81-y-old man with COPD, cough, and sputum showing a large right-side upper-lobe cavitary process with bilateral apical pleural thickening. Multiple sputum specimens were acid-fast bacilli smear negative, but cultures were positive for Mycobacterium avium-intracellulare complex.

Figure 4 –

Chest CT image of a 47-y-old woman with diffuse reticulonodular infiltrates bilaterally. The patient presented with acute onset of cough, dyspnea, and low-grade fever after swimming. A diagnosis of hypersensitivity pneumonitis was made, and etiology was traced to Mycobacterium avium exposure at the pool.