Electron microscopic observations of the relationship between peripheral nerve tissue proper and an endoneurial capillary in a dermal lesion of relapsed lepromatous patient.

The origin of relapse in clinically cured leprosy patients and the dissemination of Mycobacterium leprae in such patients are hitherto little understood phenomena. A detailed electron microscopical examination of a small dermal nerve in a lepromatous lesion of a presently relapsed patient was carried out. Our observations showed the presence of M. leprae in Schwann cells, perineurial cells, vacuolar spaces located in axoplasm and elsewhere. The course of a capillary, entering the endoneurium from the epineurium via the perineurium, suggested the possibility of hematogenous spread of M. leprae which had been tucked away in the dermal peripheral nerve. At the time of relapse, bacilli may multiply in the nerve, may enter the bloodstream, and thus disseminate from the nerve into other nerves and other tissues via hematogenous spread.