Although production of proinflammatory cytokines, such as Interferon gamma (IFN-γ) and tumor necrosis factor-α (TNF-α), is important for Leishmania killing, an overproduction of these proinflammatory cytokines as well as a decreased ability of IL-10 and TGF-β to modulate this response may lead to severe tissue damage that have been seen in mucosal leishmaniasis patients compared to patients with classical cutaneous leishmaniasis. This evidence concerns the gene IFNG and cutaneous leishmaniasis.