It has been difficult to identify distinct susceptibility genes in PBC so far. Genetic associations in PBC were shown with major histocompatibility complex encoded genes. PBC is apparently associated with the DRB1*08 family of alleles, although marked variation is observed between different ethnic groups. Association with the DRB1*0801-containing haplotype is seen in populations of European origin, whereas in populations of Asian origin, an association is seen with the DRB1*0803 allele. A protective association has been described with DRB1*11 and DRB1*13, but once again, significant population differences are observed [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] . Both associations of PBC with the DRB1*08 allele as well as the protective association of DRB1*11 and DRB1*13 were recently confirmed in the largest series ever reported including 664 unrelated patients from Italy [103] . The odds ratio for developing PBC was 3.3 for DRB1*08-positive subjects, whereas it was reduced to 0.3 for subjects positive for DRB1*11, to 0.7 for DRB1*13, and to 0.1 for carriers of both DRB1*11 and DRB1*13. This study again highlighted the relevance of geographic variation, with marked differences in allele association between northern and southern Italy.