Inclusion Criteria:  Age 18 or above IgG4 related disease patients with pancreatobiliary involvement receiving care in the GI clinic of the participating centers  The diagnosis of IgG4 related disease was made either by:  an elevated serum IgG4 serology level with typical features of pancreatobiliary involvement on imaging (eg, CT / MRI), and/or endoscopic ultrasound (EUS), and/or endoscopic retrograde cholangiopancreatography (ERCP), or an elevated serum IgG4 serology level with typical histopathologic features of the disease (eg, lymphoplasmacytic infiltration, obliterative phlebitis, and storiform fibrosis) on surgical pathology (eg, biopsy during surgery or surgical resection specimen) or endoscopic biopsies (eg, EUS guided fine needle biopsy).  Exclusion Criteria:  1) Patients who have an alternative diagnosis (i.e., non-IgG4 disease) despite an elevated serum IgG4 level