In contrast, Mendelian Susceptibility to Mycobacterial Disease (MSMD) constitutes an atypical PID caused by defects in IFN-γ-mediated immunity, leading to the selective predisposition to intermacrophagic infections, mostly Mycobacteria and Salmonella (Boisson-Dupuis et al., 2015; Bustamante, 2020). The gene discussed is IFNG; the disease is Mendelian susceptibility to mycobacterial diseases.