Autosomal recessive (AR) mendelian susceptibility to mycobacterial diseases (MSMD) due to partial IFN-gammaR1 deficiency is a genetic variant of MSMD (see this term) characterized by a partial deficiency in IFN-gammaR1, leading to a residual response to IFN-gamma and, consequently, to recurrent, moderately severe infections with bacillus Calmette-Guérin (BCG) and other environmental mycobacteria (EM).