Several MSMD patients, particularly those with IFN-γR1 [57,58] and IL-12p40 [59] deficiencies, have been shown to suffer from infections due to both weakly virulent mycobacteria and M. tuberculosis, raising the question as to whether the TB observed in these patients could also be attributed to a monogenic predisposition. Here, IFNGR1 is linked to Mendelian susceptibility to mycobacterial diseases.