Fibrosis: a distinguishing feature in the pathology of neural leprosy

Abstract

Fibrosis in the peripheral nerve is the end stage of leprous neuropathy. The present study describes its frequency, characterization, and pathogenic development. Six hundred and thirteen nerve samples were sorted from 278 neural leprosy (NL) and 335 non-leprosy neuropathy patients (ON). The total number of samples were histologically examined by routine staining methods (hematoxylin-eosin, Wade staining, and Gomoris trichrome) while fibrosis was evaluated via semiquantitative estimation. Fibrosis was most frequent in the NL group (33% against 0.4% in ON) in association with endoneurial microfasciculation in 41% of the NL samples. Pericytic activation in the perivascular environment was confirmed to be the source of the fibroblasts and perineurial cells delimiting microfascicles. End-stage fibrosis in leprosy depicts an arrangement of microfascicles devoid of neural components (Schwann cells and axons), lined by an intermediate phenotype of fibroblastic-perineurial cells, and filled by bundles of collagen fibers. The present study both underscores that fibrosis is frequently the very severe end stage of neural leprosy pathogeny by analyzing the peculiarly distinct development of fibrosis within the neural environment.