While IgG4 remains the most specific serologic marker, integrating IgE measurement offers additive value, particularly in cases with atypical IgG4 levels (e.g., 9% of IgG4-RD patients have normal IgG4 at diagnosis, of whom only 1 had elevated IgE). Here, IGHE is linked to immunoglobulin G4-related sclerosing disease.