The pathogenesis of IgG4-RD is poorly understood; however some findings are consistent with multiple immune-mediated mechanisms [8]: class II histocompatibility antigen genotype; autoantibodies to lactoferrin and carbonic anhydrase II; possible molecular mimicry involving Helicobacter pylori; immune complex deposition in some affected organs; increased levels of Th2 cytokines, T regulatory cells, interleukin-10, and transforming growth factor; evidences of allergic response with peripheral eosinophilia. Here, CA2 is linked to immunoglobulin G4-related sclerosing disease.