Leprosy is a contagious infectious disease caused by the bacillus Mycobacterium leprae. Although it is curable with therapy, it is still highly prevalent in underdeveloped areas. This systematic review sought to contemplate the innumerable variables involved in the disease’s persistence within certain populations, as in Brazil, despite eradication efforts. Variables verified in its pathogenesis include human leukocyte antigen, toll-like receptor, polymorphism, antibodies, cytokines and cellular immune response. Leprosy reactions are also under the influence of elements that comprise the immune system. On the other hand, lesions emerge due to tropism from the etiological agent through peripheral nerves by means of the linkage of phenolic glycolipid 1 to Schwann cells. The clinical condition of this pathology is related with the host immune condition, originating seven clinical forms that are classified according to clinical, histo pathological, bacteriological, and immune conditions. The diagnosis is based on clinical symptoms and on micro scopical detection of acid-resistant bacilli in skin smears. A multidrug therapy is used as treatment according to the number of lesions the patient presents. Prophylaxis and control depend on early diagnosis and active search of persons under risk of acquiring the disease. Many studies have been carried out but there is much to be explored in researches for the elucidation of the disease’s chain of transmission, etiopatho genesis, diagnosis, and treatment.