Variants of MSMD-causing genes disrupt the production of IFNγ (IFNG, IL12B, IL12RB1, IL12RB2, IL23R, ISG15, MCTS1, RORC, TBX21, TYK2), the response to IFNγ (CYBB, JAK1, IFNGR1, IFNGR2, STAT1, USP18) or both (IRF1, IRF8, NEMO, SPPL2A), or the recruitment of monocytes (CCR2)7–14. This evidence concerns the gene IFNG and Mendelian susceptibility to mycobacterial diseases.