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). Here, IFNGR1 is linked to Mendelian susceptibility to mycobacterial diseases.