“Reactions in Leprosy: Updated Insights Into Pathophysiology, Clinical Spectrum, and Therapeutic Approaches—A Narrative Review”

ABSTRACT Background and Aims Reaction in leprosy is an immune‐mediated acute inflammatory episodes that occur in the natural course of Hansen's disease. Reaction can occur before, during, or after starting multidrug therapy and is a major cause of nerve damage, morbidity, and disability in affected individuals. The aim of this review is to provide a comprehensive overview on the pathophysiology, clinical manifestations, and current management strategies for reactions in leprosy. Methods A narrative review of published literature was conducted focusing on the risk factors, immunopathogenesis, clinical presentation, severity scoring, diagnostic challenges, and therapeutic approaches of Type 1 (reversal reaction), Type 2 (Erythema Nodosum Leprosum), and Type 3 (Lucio phenomenon) leprosy reactions. Relevant studies, guidelines, and reviews were analyzed using the databases PubMed, Scopus, and Google Scholar from 2005 to 2025, to provide an updated synthesis of knowledge. The keywords used included: “leprosy reactions”, “type 1 reaction”, “type 2 reaction”, “lucio phenomenon”, “immunopathogenesis”, “clinical presentation”, “severity scoring”, and “management”. Articles were screened based on relevance to the topic and selected through consensus among the authors. Results Type 1 leprosy reaction is a delayed‐type hypersensitivity response due to enhanced cell‐mediated immunity, leading to the aggravation of pre‐existing skin lesions and neuritis. Type 2 reaction is an immune‐complex mediated phenomenon associated with systemic symptoms along with the fresh appearance of reddish subcutaneous nodules. Lucio phenomenon, which is due to endothelial cell injury, usually presents with tender purpura on the extremities which becomes necrotic and ulcerated. Management can be tailored according to the severity of the reactional episode. Conclusion Swift identification of leprosy reaction is important as it can be the first manifestation of leprosy in a large number of patients, and if not treated at an early stage, it may lead to deformity and disability.