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The familial predisposition to chronic inflammatory bowel disease and the increased concordance rate in monozygotic twins with Crohn's disease, suggest that genetic factors influence disease susceptibility. A 100% association with the supertypic HLA class II specificity DRw52a was recently described in white North American patients with primary sclerosing cholangitis, with or without concurrent ulcerative colitis. HLA class II alleles of the DR, DQ, and DP subregions were determined by genomic typing techniques in a large group of Swedish patients with ulcerative colitis or Crohn's disease as well as in a series of patients with primary sclerosing cholangitis. No statistically significant HLA class II association was observed in any of the investigated diseases or when the patients were subgrouped according to disease site or occurrence of extraintestinal manifestations, except an insignificant increase of the DRw17, DQw2 haplotype in patients with primary sclerosing cholangitis. The failure to confirm the well established DRw17 association in Swedish patients with sclerosing cholangitis probably represents a statistical type II error. Furthermore, this study did not verify the recently described strong DRw52a association in sclerosing cholangitis--52% of the patients were DRw52a positive compared with 28% of the controls (p less than 0.05, pc NS). This discrepancy was probably caused by different typing techniques. The DRw52a specificity was determined directly by hybridising HLA-DRB3 genes, group specifically amplified by the polymerase chain reaction, with an allele specific oligonucleotide probe, whereas in the previously mentioned study DRw52a was assigned by indirect serological criteria, which overestimate the frequency of this allele.