This fact can be justified by the higher prevalence of multibacillary forms in non-co-infected patients and of paucibacillary forms in co-infected patients, according to the paradox of leprosy in patients living with HIV [15,39], and, since, as reported in previous studies, multibacillary forms present higher expression of this neurotrophin [35,47]. Here, BDNF is linked to leprosy.