Intravenous Immunoglobulin in Idiopathic Inflammatory Myopathies: a Practical Guide for Clinical Use

Purpose of Review: Idiopathic inflammatory myopathies (IIM) are a complex family of autoimmune systemic disorders which often affect muscle and/or skin. IIM cause significant morbidity and mortality, but optimal treatment is uncertain. This review provides a practical guide for using intravenous immunoglobulin (IVIG) and subcutaneous immunoglobulin (SCIG) in the management of IIM, including dermatomyositis (DM), polymyositis (PM), immune-mediated necrotizing myositis (IMNM), and spontaneous inclusion body myositis (IBM), based on relevant recent literature and experience. We summarize pertinent considerations when using IVIG in special circumstances, including myositis-related dysphagia, interstitial lung disease (ILD), calcinosis cutis, and pregnant patients. This review also discusses IVIG safety, available formulations, and costs. Recent Findings: While IVIG has been used de facto for severe IIM for over 30 years, prior clinical trials of IVIG were notably limited. Recently, however, IVIG has proven safe and effective against IIM in several high-impact publications, including a large prospective, randomized placebo-controlled phase III study in DM. Summary: IVIG is useful against both muscular and extra-muscular manifestations in many types of IIM. It can be used as a first-line, steroid-sparring agent or as add-on to other treatments, tailored to specific clinical IIM scenarios. It is generally well-tolerated and has good safety profile, but accessibility and cost still limit its use.