The identification of IFN-γ receptor deficiencies (IFNGR1 and IFNGR2) in patients with Mendelian susceptibility to mycobacterial disease (MSMD) demonstrated that IFN-γ plays a critical and non-redundant role in controlling mycobacterial infections (Rosain et al. 2019). The gene discussed is IFNGR2; the disease is Mendelian susceptibility to mycobacterial diseases.