A systematic review and meta-analysis of mycobacterial infections in patients with idiopathic inflammatory myopathies

Objectives Infections including tuberculosis (TB) are a leading cause of morbidity and mortality in idiopathic inflammatory myopathies (IIM). We systematically reviewed the prevalence of mycobacterial infections in patients with IIM. Methods We screened PUBMED, EMBASE and SCOPUS databases and conference abstracts (2015-20) for original articles using Covidence. Pooled estimates of prevalence were calculated. Results Of 83 studies (28 cohort studies, two case control and 53 case reports), 19 were analysed. Of 14 043 IIM patients, DM (54.41%) was the most common subset among TB. Most studies were from Asia with high prevalence (5.86%, 2.33%-10.60%). Pooled prevalence of mycobacterial infections among IIM was 3.58% (95% CI: 2.17%, 5.85%, P < 0.01). Disseminated and extrapulmonary forms (46.58%; 95% CI: 39.02%, 54.31%, P = 1.00) were as common as pulmonary TB (49.07%; 95% CI: 41.43%, 56.75%, P =0.99) both for I-2=0. Muscle involvement, an otherwise rare site, was frequently seen in case reports (24.14%). M. tuberculosis (28.84%) was the most common pathogen followed by Mycobacterium avium complex (3.25%). Non-tuberculous mycobacteria were less common overall (6.25; 95% CI: 3.49%, 10.93%) I-2=0, P =0.94. Subgroup analysis and meta-regression based on high vs low TB regions found prevalence 6.61% (2.96%, 11.33%) in high TB regions vs 2.05% (0.90%, 3.56%) in low TB regions. While death due to TB was occasionally reported (P =0.82), successful anti-tubercular treatment was common (13.95%). Conclusion TB is common in IIM, particularly in endemic regions though current data is largely heterogeneous. Extra-pulmonary forms and atypical sites including the muscle are frequent. Limited data suggests fair outcomes, although larger prospective studies may offer better understanding.