HLA-DRB1 and pancreatic serous cystadenoma: However, the HLA-DRB1*15:01, reported to represent a risk allele in PSC (60), was found to be protective to all forms of paediatric autoimmune diseases in an ethnically similar population, suggesting that HLA polymorphisms are only a component of the complex etiopathogenesis of AIH, ASC and PSC.