The MIGHT Trial - An Exploratory Clinical Trial of IVIG in Anti-HMGCR Immune Mediated Necrotizing Myopathy

Inclusion Criteria: * Age \> 16 years * Anti-HMGCR antibody positive * MMT-8 score \< 142 (range 0-160) * Serum CK \> 5x upper limit of normal * Anti-HMGCR IMNM disease duration \< 36 months at screening * No moderate or severe respiratory or swallowing dysfunction due to anti-HMGCR IMNM at screening * No history of dermatomyositis rash * Must reside in a state with a participating research site Exclusion Criteria: * Oral glucocorticoid (GC) daily dose \> 15mg at screening * Change in oral GC dose \< 2 weeks prior to screening * Prior IVIG treatment for anti-HMGCR IMNM -\>1 oral conventional synthetic DMARD (e.g. methotrexate, mycophenolate mofetil, azathioprine) use at screening * Change in concomitant DMARD dose \< 4 weeks prior to screening * Rituximab \< 6 months prior to screening * Plasma exchange, cyclophosphamide, or biologic immunosuppressive medication \< 3 months prior to screening * Use of statin medication at screening * History of anaphylactic reaction to IVIG * History of angina pectoris, myocardial infarction, transient ischemic attack, or stroke \< 12 months prior to screening * Females of child-bearing potential who are pregnant, breastfeeding, or are unwilling to practice a highly effective method of contraception during the study * Wells Criteria for DVT score of 2 or more at screening * Wells Criteria for PE score of 4 or more at screening * Weight \>120kg * History of cancer (excluding non-melanomatous skin cancer) \< 5 years prior to screening * History of pulmonary embolism or deep venous thromboembolism \< 3 years prior to screening * History of hyperviscosity or hypercoagulable state * Currently receiving anti-coagulation therapy (vitamin K antagonists, non-vitamin K oral anticoagulants \[e.g. dabigatran, rivaroxaban, apixaban\], parenteral anticoagulants \[e.g. fondaparinux\]. Note that oral anti-platelet agents are allowed (e.g. aspirin, clopidogrel, ticlopidine). * Glomerular filtration rate (GFR) \<60mL/min at the time of screening * Any medical condition which, in the investigator's judgment, makes participation in the clinical trial unadvisable or which would interfere with evaluation of the study treatment.