A genetic variant of mendelian susceptibility to mycobacterial diseases (MSMD) with characteristics of 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. These infections are recurrent but less severe than those seen in MSMD due to complete IFN-gammaR1 and IFN-gammaR2 deficiencies. Caused by homozygous mutations in the IFNGR1 gene on chromosome 6q23-q24 that encodes the IFN-gamma receptor ligand binding chain. The most common mutation is, by far, I87T. This mutation leads to the expression of IFN-gamma receptors on the cell surface with no signal transduction capacity and they therefore only show a partial response to IFN-gamma. Transmission is autosomal recessive.