Do you recommend discontinuing IVIG for a newly diagnosed HMGCR+ statin induced necrotizing myopathy who developed a recent brachial DVT?

Really, the issue is if the DVT was provoked or not. If possibly not provoked then would decrease the dose of IVIG or give it over a long time frame. For example, if the patient is on 2 gm/kg over 2 days, I would do 2 gm/kg over 4 days. Or reduce the dose to 1 gm/kg over 2 days.

Of note, in the large phase 3 ProDERM trial of Octagam 20% IVIG for DM led by Dr. @Dr. First Last and colleagues, the incidence of IVIG-associated thromboembolic events seemed highly dependent on the infusion rate of the IVIG preparation:

Interim safety analyses during the trial led to a protocol amendment that reduced the maximum allowable IVIG infusion rate from 0.12 mL/kg/min to 0.04 mL/kg/minute. The incidence of thromboembolic events subsequently dramatically fell by almost 30% (from 1.54 to 0.54 per 100 patient months) after this amendment.