IgG4 related disease is a very recently established medical
label and there's very little medical literature on IgG4 RD.
I would imagine that the number of IgG4 specialists would be extremely limited, in light of the very low incidence of
IgG4 RD.
In other words, this might be the reason your Rheumatologist
referred you to a specialist several states away.
Would this be in Massachusetts, perhaps?
Mass General is one of the few US hospitals which is a pioneer in research and treatment of IgG4 RD.
Best wishes,
Niko