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.