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, 2 case-control and 53 case reports), 19 were analysed. Of 14043 IIM patients, Dermatomyositis (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 I2=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%) I2=0, p= 0.94.Subgroup analysis & 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 &atypical sites including the muscle are frequent. Limited data suggests fair outcomes, although larger prospective studies may offer better understanding.