Electron microscopy of Mycobacterium leprae in cutaneous nerve components

Cutaneous nerves in lepromatous lesions from ninety-six patients were observed by electron microscopy. The regenerative process of myelinated fibers was evident within lepromatous tissues. Intact or degenerative forms of Mycobacterium leprae were surrounded by the electron transparent substance within the axoplasm and Schwann cell cytoplasm. In contrast, the microenvironment of M. leprae in macrophages was characterized with fusing lysosomes and foamy structures. These results suggest that the electron transparent substance may be derived from bacterial metabolites and also that the foamy structure may originate from lysosomal substance.