Leprosy: Comprehensive insights into pathology, immunology, and cutting-edge treatment strategies, integrating nanoparticles and ethnomedicinal plants

Mycobacterium leprae is the causative agent responsible for the chronic disease known as leprosy. This condition is characterized by dermal involvement, often leading to peripheral nerve damage, sensory-motor loss, and related abnormalities. Both innate and acquired immunological responses play a role in the disease, and even in individuals with lepromatous leprosy, there can be a transient increase in T cell immunity during lepromatous reactions. Diagnosing of early-stage leprosy poses significant challenges. In this context, nanoparticles have emerged as a promising avenue for addressing various crucial issues related to leprosy. These include combatting drug resistance, mitigating adverse effects of conventional medications, and enhancing targeted drug delivery. This review serves as a comprehensive compilation, encompassing aspects of pathology, immunology, and adverse effects of multidrug delivery systems in the context of leprosy treatment. Furthermore, the review underscores the significance of ethnomedicinal plants, bioactive secondary metabolites, and nanotherapeutics in the management of leprosy. It emphasizes the potential to bridge the gap between existing literature and ongoing research efforts, with a profound scope for validating traditional claims, developing herbal medicines, and formulating nanoscale drug delivery systems that are safe, effective, and widely accepted.

Leprosy: Clinical aspects and diagnostic techniques

Leprosy, also known as Hansen's disease, is a curable infectious disease that remains endemic in >140 countries around the world. Despite being declared "eliminated" as a global public health problem by the World Health Organization in the year 2000, approximately 200,000 new cases were reported worldwide in 2017. Widespread migration may bring leprosy to nonendemic areas, such as North America. In addition, there are areas in the United States where autochthonous (person-to-person) transmission of leprosy is being reported among Americans without a history of foreign exposure. In the first article in this continuing medical education series, we review leprosy epidemiology, transmission, classification, clinical features, and diagnostic challenges.

Clinical aspects of leprosy

Leprosy is a chronic, infectious disease caused by Mycobacterium leprae. It mainly affects the peripheral nervous system, skin, and certain other tissues such as the reticulo-endothelial system, bones and joints, mucous membranes, eyes, testes, muscles, and adrenals. Leprosy clinical presentation varies from few to widespread lesions. In most patients, early leprosy presents as macular and hypopigmented lesions. This initial clinical presentation is known as indeterminate leprosy and occurs in individuals who have not developed cell-mediated immunity against M. leprae yet. The number of lesions depends on the genetically determined cellular immunity of the patient. Individuals presenting a vigorous cellular immune response and limited humoral immune responses to M. leprae, usually present few skin lesions. Without treatment, those patients tend to evolve into the polar tuberculoid or borderline tuberculoid form of leprosy. Due to the inability to mount an effective cellular-mediated response to M. leprae and the consequent hematogenous spread of the bacilli, some patients may present with numerous and symmetrically distributed hypochromic lesions. Without treatment these patients evolve to a nonresistant form of leprosy, polar lepromatous.