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). The gene discussed is IFNGR1; the disease is Mendelian susceptibility to mycobacterial diseases.