Mutations in 21 different genes (IFNGR1, IFNGR2, IFNG, IL12RB1, IL12RB2, IL23R, IL12B, ISG15, USP18, ZNFX1, TBX21, STAT1, TYK2, IRF8, CYBB, JAK1, RORC, NEMO, SPPL2A, MCTS1, and IRF1) with more than 35 different genetic etiologies of MSMD have been described [12,13,14,15,16,17,18]. Here, IL23R is linked to Mendelian susceptibility to mycobacterial diseases.