Very high serum IgG4 does not equal IgG4-related disease. Most of the time (3/4 in this sample), IgG4>5xULN is IgG4-RD. Some of the time, it's not. (Could be a long list of things) Criteria are useful High serum IgG4 alone isn't enough @zach_wallace_md #ACR21 ABST1103 @RheumNow https://t.co/oxMgnnpIce