Slight elevations of IgG4 concentration are seen also in other diseases such as pancreatic cancer.20 Furthermore, between 3–30% of IgG4-RD patients have normal serum IgG4 concentrations;21 however, they may suffer from significant disease including AIP with IAC.5 Different IgGs bind to different receptors and distinct genes encode six human receptors for IgG.22 IgG1 and IgG3 bind to all human receptors for IgG; IgG2 binds not only to FcγRIIAH131, but also has a lower affinity to FcγRIIAR131 and FcγRIIIAV158; IgG4 binds to FcγRI, FcγRIIA, IIB and IIC and FcγRIIIAV158. This evidence concerns the gene IGHG3 and familial pancreatic carcinoma.