Peripheral nerve biopsy in pure neural leprosy: a 26-year experience in Brazil.

Brazil ranks second globally in leprosy burden, with approximately 25 000 cases reported in 2022. This study aimed to analyse the 26-year experience (1997-2023) in nerve biopsies at a specialized leprosy outpatient clinic, focusing on their usefulness in diagnosing peripheral neuropathy in patients with clinical and neurophysiological features suggestive of leprosy but lacking dermatological lesions. Tissue samples were preserved in glutaraldehyde, buffered formalin and liquid nitrogen, with histopathological analysis using various staining techniques and molecular testing on frozen material. In 819 cases, 529 were diagnosed with leprosy (64.6% overall leprosy diagnosis rate), and 207 pure neural leprosy cases were confirmed. Other conditions identified included vasculitis, diabetic neuropathy and amyloidosis, while 16.5% of cases yielded inconclusive results. The predominant clinical symptoms included sensory disorders (85.7%), localized paraesthesia (70.3%) and muscle weakness (59.4%), with multiple mononeuropathies frequently observed on electroneuromyography. The most biopsied nerves were the ulnar cutaneous branch (50.6%), sural (37.2%) and superficial peroneal (6.8%). Nerve biopsy proved valuable for confirming leprosy and distinguishing differential diagnoses in complex cases, particularly when clinical findings alone were insufficient. Integrating clinical-pathological correlation optimized diagnostic accuracy, underscoring the importance of this tool in managing suspected neural leprosy and guiding treatment in challenging cases.