Japanese Society of Internal Medicine Acta Medica Okayama 0918-2918 65 10 2026 Mycobacterium intracellulare Infection in a Japanese Patient with Signal Transducer and Activator of Transcription-3 Gain-of-function Syndrome 1421 1430 EN Hideharu Hagiya Department of Infectious Diseases, Okayama University Hospital Yoshiaki Soejima Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kazuki Tokumasu Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Yoji Hirai Department of Dermatology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Yuki Otsuka Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Marina Kawaguchi Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Shinnosuke Fukushima Department of Infectious Diseases, Okayama University Hospital Kenta Nakamoto Department of Infectious Diseases, Okayama University Hospital Kohei Oguni Department of Infectious Diseases, Okayama University Hospital Yusuke Shiode Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kazuhiro Uda Department of Pediatrics, Okayama University Hospital Masato Yashiro Department of Pediatrics, Okayama University Hospital Kousei Hasegawa Department of Pediatrics, Okayama University Hospital Koji Iio Microbiology Division, Clinical Laboratory, Okayama University Hospital Fumio Otsuka Department of General Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Signal transducer and activator of transcription-3 (STAT3) gain-of-function (GOF) syndrome predisposes patients to autoimmunity diseases. Yet, nontuberculous mycobacterial (NTM) infections have rarely been described. We herein report a teenage Japanese patient with genetically confirmed STAT3-GOF syndrome who developed Mycobacterium intracellulare disease. Combination antimycobacterial chemotherapy reduced the bacterial burden; however, the refractory NTM infection relapsed after initiation of adjunctive tofacitinib therapy. The present case demonstrates that host-directed therapy must be combined with prolonged antimycobacterial regimens to control drug-resistant NTM in patients with inborn errors of immunity. No potential conflict of interest relevant to this article was reported.