Efficacy and safety of intravenous and subcutaneous immunoglobulin therapy in idiopathic inflammatory myopathy: A systematic review and meta-analysis

Objective: To perform a systematic review and meta-analysis on the efficacy and safety of intravenous (IVIg) and subcutaneous (SCIg) immunoglobulin (Ig) therapy in the treatment of idiopathic inflammatory myopathy (IIM) and juvenile dermatomyositis (JDM). Methods: PubMed, Embase and SCOPUS were searched to identify studies on Ig therapy in patients with IIM and/or JDM (2010−2020). Outcome measures were complete response (CR) or partial response (PR) in terms of muscle power and extramuscular disease activity measures on the International Myositis Assessment and Clinical Studies Group (IMACS) core set domains. Results: Twenty-nine studies were included (n = 576, 544 IIM, 32 JDM). Muscle power PR with pooled Ig therapy was 88.5% (95% confidence interval (CI): 80.6–93.5, n = 499) and PR with SCIg treatment was 96.61% (95% CI: 87.43–99.15, n = 59). Pooled PR with first-line use of IVIg was 77.07% (95% CI: 61.25–92.89, n = 80). Overall, mean time to response was 2.9 months (95% CI: 1.9–4.1). Relapse was seen in 22.76% (95% CI: 14.9–33). Studies on cutaneous disease activity and dysphagia showed significant treatment responses. Glucocorticoid and immunosuppressant sparing effect was seen in 40.9% (95% CI: 20–61.7) and 42.2% (95% CI: 20.4–64.1) respectively. Ig therapy was generally safe with low risk of infection (1.37%, 95% CI: 0.1–2.6). Conclusions: Add-on Ig therapy improves muscle strength in patients with refractory IIM, but evidence on Ig therapy in new-onset disease and extramuscular disease activity is uncertain.