Can physics principles help explain why non-tuberculous mycobacterial lung disease is more severe in the right middle lobe and lingula?

Pulmonary Nontuberculous Mycobacteria Infection in Bronchiectasis: A Narrative Review of Current Status and Future

Background and Aims

Pulmonary nontuberculous mycobacteria (NTM) infection and bronchiectasis are two distinct respiratory conditions, but bronchiectasis and pulmonary NTM infections are closely associated. NTM can cause bronchiectasis. However, bronchiectasis can create a favorable environment for NTM colonization and exacerbate the progression of NTM. Managing both conditions typically requires a comprehensive approach that addresses infection and the underlying structural lung damage.

Methods

To perform this review, the author retrieved and assessed relevant articles related to NTM and bronchiectasis that have been published to date from databases, including PubMed/MEDLINE, Scopus, and Google Scholar.

Results

In this review, the close relationship between pulmonary NTM and bronchiectasis is described from the viewpoints of diagnosis, epidemiology, Pseudomonas aeruginosa, host susceptibility, females and NTM, and treatment.

Conclusion

Timely diagnosis and management of NTM infections, especially in individuals with underlying risk factors, are essential to prevent disease progression and improve the quality of life of affected individuals.

Histopathologic Analysis of Surgically Resected Lungs of Patients with Non-tuberculous Mycobacterial Lung Disease: a Retrospective and Hypothesis-generating Study

Non-tuberculous mycobacterial lung disease (NTM-LD) is most commonly due to species within the Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MAbC). Surgical lung resection, typically a lobectomy or segmentectomy, is occasionally undertaken for individuals with recalcitrant but localized NTM-LD. Since the growth characteristics of MAC (slow growers) and MAbC (rapid growers) as well as their drug susceptibility patterns are significantly different, the objective of this study is to characterize and compare the histopathologic features of the resected lungs due to these two major NTM groups. From 1996 to 2017, 356 patients with NTM-LD due to MAC (n=270), MAbC (n=54), or both (n=32) underwent a total of 404 lobar resections (with the lingula counted as a separate lobe) at the University of Colorado Hospital. We analyzed by microscopy the existing surgical lung tissue sections for bronchiolitis, bronchiolectasis, bronchiectasis, non-necrotizing granuloma (airway, parenchymal, and total), necrotizing granuloma (airway, parenchymal, and total), peri-airway fibrosis, fibrous pleuritis, and lymphoid follicles. There were no significant differences in the presence or absence of most of the histopathologic features of surgically removed lungs due to MAC, MAbC, or both MAC + MAbC. However, there were significantly more necrotizing granulomas (airway, parenchymal, and total) and fibrous pleuritis in MAC compared to MAbC lung diseases. Since necrotizing granulomas may be a sign of inadequate control of the infection, we posit that their presence may be an indication of increased chronicity, increased virulence of MAC compared to MAbC, and/or impaired host immunity against the NTM. Futures studies to determine the root cause of such differences in histopathologic findings in MAC versus MAbC lung disease may spawn new leads on differential pathogenic mechanisms with different NTM, with the goal of aiming for more targeted therapy against both the NTM and the lung damage induced by them.