Clinical, radiological, and pathological findings of non-tuberculous mycobacteria respiratory infection

Abstract

This study is designed to evaluate radiological, clinical, and pathological findings of Mycobacterium avium complex (MAC) respiratory infection. Two-hundreds of non-tuberculous mycobacteria obtained from upper respiratory tract were collected. Among them, 88 cases were selected according to the strict diagnostic criteria of MAC and chest CT findings were evaluated in 67 cases. In addition, successive chest CT findings were evaluated in 25 cases with MAC respiratory infection. Furthermore, pathological findings were evaluated in 9 surgically-resected lung specimens. Fever, hemoptysis, and dyspnea were more frequently observed in smear-positive patients than in smear-negative, culture-positive patients. Centrilobular nodules and bronchiectasis are frequent observations in patients with MAC. In addition, cavity formation was more frequently observed in smear-positive patients compared with smear negative-cases. Since the score of bronchiectasis in the second CT was significantly higher than in the first CT, progression of bronchiectasis appeared to be caused by MAC infection. Pathologically, extensive granuloma formation throughout the airways was clearly demonstrated. Immunohistochemical staining demonstrated: 1) epithelioid cells and giant cells; and 2) myofibroblasts extensively infiltrating the cavity wall. When granuloma was initially formed, no myofibroblasts were found, but as caseous necrosis appeared, the thin epithelioid cell layer was detected and the outer myofibroblast layer gradually became thick. In the cavitary wall, the layer of epithelioid cells and multinucleated giant cells surrounded necrosis, and was associated with the outer layer of myofibroblasts. In addition, the anti-TGF-beta 1 antibody stained the cytoplasm of epithelioid cells and multinucleated giant cells, preceding the advent of myofibroblasts.