Indeed, otherwise healthy patients vulnerable to weakly virulent mycobacteria (Mendelian susceptibility to mycobacterial disease [MSMD]) and/or to the more virulent Mycobaterium tuberculosis, carry inborn errors of IFN-γ, type II IFN immunity (Bustamante, 2020; Yang et al., 2020). This evidence concerns the gene IFNG and Mendelian susceptibility to mycobacterial diseases.