Light and electron microscopic appearances of peripheral nerves from two lepromatous leprosy patients after 12 months of multidrug therapy and their significance.

Biopsies from radial cutaneous nerves of a lepromatous patient and one borderline lepromatous patient treated with 12 doses of multidrug regimen were studied using light and electronmicroscopes. Histopathologically both showed typical lepromatous neuritis. Electronmicroscopic examination showed demyelination, atrophy and degeneration of myelinated axons and nonmyelinated axons and a marked increase in collagen fibrils. Perineurial cells, Schwann cells and endoneurial macrophages contained numerous persisting M. leprae. Almost all the organisms in macrophages were fragmented and could be considered non-viable. A few M. leprae found in Schwann cells showed structure of viable bacilli. It is possible a few dead or dormant organisms may persist for many years in Schwann cells or in fibrous tissue without producing any ill effects, and may cause relapse only in rare instances. Since 12 months of MDT resulted in the clearance of M. leprae in course of time and the reported relapse rates after years were insignificant, implementation of MDT for a year for all MB patients is justified provided surveillance of these patients is ensured. Administration of uniform MDT for 6 months is worth a trial.