We present a case of a 42-year-old woman with Mendelian susceptibility to mycobacterial disease. The disease was diagnosed at an adult age with relatively typical clinical manifestations; the skeleton, joints, and soft tissues were affected by nontuberculous mycobacteria: Mycobacterium lentiflavum, M. kansasii, and M. avium. A previously published loss-of-function and functionally validated variant NM_000416.2:c.819_822delTAAT in IFNGR1 in a heterozygous state was detected using whole-exome sequencing. After interferon-γ therapy was started at a dose of 200 µg/m2 three times a week, there was significant clinical improvement, with the need to continue the macrolide-based combination regimen. In the last 4 months, she has been in this therapy without the need for antibiotic treatment.