Investigation of human genes under pathogen-driven selection as Plasmodium sp. has pinpointed genetic variants that participate in the adaptation to the environment and/or are related to severities of human diseases. The current study examined an example of an evolutionary trade-off in which genetic variants in the PKLR gene putatively selected for malaria resistance influence the susceptibility to mycobacterial diseases (leprosy and tuberculosis) in Brazilian population and Mozambique. A complete characterization of the biological effect of those risk variants may clarify the role of the PKLR gene in leprosy and tuberculosis. Deciphering the genetic basis of mycobacterial diseases has implications for the identification of true high-risk individuals in order to optimize screening strategies. Furthermore, the trade-off mechanism discussed in this work might occur in other central genes of immune response and biochemical pathways, controlling the susceptibility to other infectious diseases.