Since the time of Bible, leprosy has been recognized to be caused by the mycobacterium leprae. It remains prevalent in many parts of the world and affects Brazil's public health. In Brazil, the prevalence rate in 2011 was 1.54 cases per 10,000 people. Leprosy is spread by prolonged intimate contact between genetically predisposed and sensitive people and untreated multibacillary patients. Bacilli seen in upper airway discharge that are inhaled during transmission. The primary entrance or departure point for M. leprae is the nasal mucosa Understanding of the pathogenesis, variations in clinical characteristics, and progression of the disease have been aided by increased knowledge of the structural and biological characteristics of M. leprae, its genome's sequencing, and the mechanisms of host immune response against the bacilli, which are dependent on genetic susceptibility. In this study, etiopathogenic, clinical, and epidemiological aspects of leprosy are updated for dermatologists.