Nitrotyrosine localization to dermal nerves in borderline leprosy

Background Nerve damage is a common and disabling feature of leprosy, with unclear aetiology. It has been reported that the peroxidizing agents of myelin lipids—nitric oxide (NO) and peroxynitrite—are produced in leprosy skin lesions. Objectives To investigate the localization of nitrotyrosine (NT)—a local end‐product of peroxynitrite—in leprosy lesions where dermal nerves are affected by a granulomatous reaction. Methods We investigated by immunohistochemistry and immunoelectron microscopy the localization of the inducible NO synthase (iNOS) and NT in biopsies exhibiting dermal nerves from patients with untreated leprosy. Results There were abundant NT‐positive and iNOS‐positive macrophages in the borderline leprosy granulomas infiltrating peripheral nerves identified by light microscopy, S‐100 and neurofilament immunostaining. Immunoelectron microscopy showed NT reactivity in neurofilament aggregates and in the cell wall of Mycobacterium leprae. Conclusions Our results suggest that NO and peroxynitrite could be involved in the nerve damage following borderline leprosy.