Leprosy: a modern assessment of an ancient neglected disease

Leprosy or Hansen's disease is a chronic mycobacterial infectious disease caused by Mycobacterium leprae and affects mainly peripheral nerves and skin as well as upper respiratory mucosae. This infection is a conjoined bacteriological and immunological disease. Target cells of infection are macrophages, histiocytes in the skin, and the nonmyelinating and myelinating Schwann cells in the peripheral nerves leading to axonal dysfunction and demyelination leading to functional impairment and deformity. Leprosy reactions represent the most important determinant of nerve impairment if untreated and unrecognized. Control of leprosy transmission remains a challenge despite substantial improvements through the use of multidrug therapy in many settings. Most importantly, although many patients have been microbiologically cured through the efforts of the World Health Organization, many are left with significant disability that has recently been estimated to be similar to 20% of those treated (similar to 15 million individuals) in the last decades. Further efforts are needed to elucidate the epidemiology and risk factors for disability among those with multibacillary forms.