Of these, 23 (50%) were diagnosed with Mendelian susceptibility to mycobacterial disease (MSMD), involving mutations in the IL12RB1, STAT1, IFNGR1, SPPL2A, TYK2, and TBX21 (T-bet) genes. The gene discussed is IFNGR1; the disease is Mendelian susceptibility to mycobacterial diseases.