Clinical characteristics of extrapulmonary nontuberculous mycobacterial disease in Japanese adult patients without HIV: A multicenter retrospective study

Objectives The incidence of nontuberculous mycobacteria (NTM) infections has increased globally. We describe clinical characteristics and outcomes of extrapulmonary NTM disease. Methods This multicenter retrospective study included adult patients with extrapulmonary NTM disease at five Japanese tertiary hospitals (2012-2020), confirmed by culture or polymerase chain reaction tests from non-pulmonary specimens. Clinical characteristics, antimicrobial therapy, source control, treatment outcomes, and mortality were evaluated. Results Seventy patients were included: 49 with rapidly growing mycobacteria (RGM) and 21 with slowly growing mycobacteria (SGM) infections. Median age was 70; 52.9% were male. Prosthetic devices were present in 38.6% of cases, more frequent in RGM than SGM (51% vs. 10%). Antimicrobials were administered to 70.0%, and 62.9% underwent source control. Treatment duration was longer for SGM (435 vs. 132 days), particularly for bone, joint, and disseminated infections. Cure/improvement occurred in 53 patients (75.7%), with similar outcomes for RGM and SGM. Among RGM infections, lack of source control in device-related cases was associated with poor treatment outcomes. Fifteen patients died during the observation period; two were NTM-related. Conclusions Most extrapulmonary NTM cases respond to antimicrobial therapy and source control. RGM infections involving prosthetic devices without source control remain challenging, warranting further research into optimized management.