We treated a 72-year-old Japanese female with sustained high fever and overall body exhaustion. An infectious liver cyst and right lung pneumonia were suspected causes. Hepatic cystectomy and various antibiotics did not resolve symptoms. Pneumonia exacerbation and ascitic fluid retention, left lumbar spinal osteomyelitis, and peri-gastric lymph node abscess penetrating the stomach were observed. Mycobacterium avium was identified in sputum, ascites, vertebral body abscess puncture specimen, and pus mucus secretion in the stomach. We diagnosed a disseminated nontuberculous mycobacterial infection. She seemed immunocompetent, without signs of AIDS or hematological malignancy. Serum anti-IFN-γ autoantibodies tested positive and were suspected to be involved in the illness onset.