Mutations in 15 genes are currently known to cause MSMD, which include IL12RB1, IL12B, IFNGR1, IFNGR2, STAT1, CYBB, IRF8, TYK2, ISG15, RORC, IKBKG, SPPL2A, JAK1, IL12RB2, and IL23R (1, 11, 12). Here, IL12RB1 is linked to Mendelian susceptibility to mycobacterial diseases.