Pathological findings of bronchiectases caused by Mycobacterium avium intracellulare complex

Abstract

It has been argued whether bronchiectasis is truly caused by MAC infection or just a predisposed condition in which MAC colonizes. Our present study was designed to evaluate the pathological findings of bronchiectases caused by Mycobacterium avium intracellulare complex (MAC) lung infection and to demonstrate MAC in the lesion of bronchiectases. A retrospective study was performed in nine cases with positive cultures for MAC in whom lung resections were performed. A determination of whether or not MAC caused pulmonary disease was made using the 1997 criteria required by the American Thoracic Society. In addition, MAC were cultured from all nine lung specimens. Pathological findings of bronchiectases were evaluated in these nine patients. Destruction of bronchial cartilage and smooth muscles layer, obstruction of airway by granulomas, and ulceration of bronchial mucosa were frequently observed. Our present study demonstrates that destruction of fundamental bronchial structure due to extensive granuloma formation throughout the airways was likely the main cause of bronchiectases in MAC infection.

Antimicrobial Susceptibility Testing, Drug Resistance Mechanisms, and Therapy of Infections with Nontuberculous Mycobacteria

“…One recent study suggested that granulomatous inflammation was the cause of bronchiectasis. In other presentations, such as that with cystic fibrosis (CF) or prior pulmonary TB, bronchiectasis clearly antedates MAC disease (123,132). For further discussion, see Risk Factors and Immunodeficiency Defects below.…”

“…The cell-mediated immune response produces an infiltration of lymphocytes, macrophages, and antigen-presenting cells. In turn, chronic inflammation leads to the destruction of the elastin layer in the bronchial walls (123).…”

Diagnostic challenges of bronchiectasis

“…Although the presence of bronchiectasis predisposes colonization by opportunistic microorganisms such as NTM, it is also suggested that they play a role in the development of these bronchial disorders. Fujita et al retrospectively evaluated resected lung specimens from 9 patients infected with Mycobacterium avium complex [13]. In all the cases they identified destruction of bronchial cartilage and of the smooth muscle layer as well as bronchial mucosa ulcerations and the presence of airway granulomas.…”

“…In all the cases they identified destruction of bronchial cartilage and of the smooth muscle layer as well as bronchial mucosa ulcerations and the presence of airway granulomas. Given these histopathological changes, the authors concluded that NTM infection could be a cause rather than a consequence of the appearance of bronchiectasis [13]. It has been suggested that certain host factors may increase the risk to develop pulmonary NTM infection [14].…”

Tools used to measure airway remodelling in research

“…In bronchiectasis, destruction of bronchial cartilage and smooth muscle layer, bronchial ulceration and obstruction of airways by granulomas are common [54]. Otherwise, little is known on detailed airway abnormalities.…”