PIK3CA and immunoglobulin G4-related sclerosing disease: In proteomic data, “Rap1 signaling pathway” and “NF-κB signaling pathway” were enriched in IgG4-RD tissue (Figure 2B), while terms such as “MAPK signaling pathway,” “PI3K-Akt signaling pathway,” “TGF-β signaling pathway,” “Ras signaling pathway,” and “Rap1 signaling pathway” were enriched in tissue transcriptomic data (Table 4, Table S7).