Genetic analysis of a large cohort of 220 MSMD patients with a defective IL-12/IL-23-IFN-γ axis ranked the presence of these mutations among MSMD patients as IL12RB1 (40%), IFNGR1 (39%), IL12B (9%), STAT1 (5%), IFNGR2 (4%), and IKBKG (3%) (Casanova et al. 1995; Filipe-Santos et al. 2006; Lee et al. 2011). Here, IFNG is linked to Mendelian susceptibility to mycobacterial diseases.