HLA-DRB1 and pancreatic serous cystadenoma: The negative prognostic impact of colitis in PSC has been consistently demonstrated in well-characterized patient cohorts and population-based series,31, 32 with more variable stratification capabilities reported for those patients having elevated serum immunoglobulin G4 (IgG4) levels.33, 34 Nevertheless, patients with PSC and high serum IgG4 also exhibit an increased frequency of HLA-DRB1*15, the presence of which may, therefore, signify a common high-risk phenotype.