Since the recognition of MSMD 25 years ago, variants of 22 genes have been implicated in this condition (CCR2, CYBB, IFNG, IFNGR1, IFNGR2, IL12B, IL12RB1, IL12RB2, IL23R, IRF1, IRF8, ISG15, JAK1, MCTS1, NEMO, RORC, SPPL2A, STAT1, TBX21, TYK2, USP18, and ZNFX1) [1–9]. This evidence concerns the gene STAT1 and Mendelian susceptibility to mycobacterial diseases.