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Approximately 80% of patients with primary sclerosing cholangitis (PSC) of Northern European origin have inflammatory bowel disease (IBD), the majority ulcerative colitis (UC). An inherent problem in interpreting positive findings in genetic association studies of PSC is thus to distinguish between factors associated with hepatobiliary versus intestinal pathology. We aimed to clarify to what extent human leukocyte antigen (HLA) class II associations in UC patients with and without PSC differ. High-resolution DRB1 and DQB1 typing was performed in 365 Scandinavian PSC patients, an independent cohort of 330 Norwegian UC patients and 368 healthy controls. HLA associations found in PSC were mostly distinct from those seen in UC, and no significant differences were noted between PSC patients with concurrent UC and PSC patients without IBD. This suggests different HLA associated genetic susceptibility to PSC and UC, and supports notions that UC in PSC may represent a distinct UC phenotype.

Background/aims: Mucosal addressin cellular adhesion molecule-1 (MAdCAM-1) has been implicated in the aberrant homing of intestinal lymphocytes to the liver in primary sclerosing cholangitis (PSC). Intercellular adhesion molecule-1 (ICAM-1) has also been implicated in the pathogenesis of PSC and the E/E genotype of the K469E polymorphism has been reported to be associated with PSC susceptibility. The aims of this study were to determine if MAdCAM-1 polymorphisms or the K469E polymorphism of ICAM-1 are associated with PSC in Scandinavia., Methods: Seven single nucleotide polymorphisms (SNPs) in MAdCAM-1 and the G421R and K469E ICAM-1 SNPs were genotyped in 365 PSC patients from Norway and Sweden. 327 Norwegian ulcerative colitis (UC) patients and 368 Norwegian bone marrow donors served as controls., Results: No significant association with PSC was found for any of the MAdCAM-1 or ICAM-1 SNPs. Allele frequencies for these polymorphisms were not significantly different between PSC patients with UC, UC patients and healthy controls., Conclusions: Polymorphisms in MAdCAM-1 are not likely to significantly affect PSC susceptibility. In addition, the E/E genotype of the K469E in ICAM-1 does not influence PSC susceptibility in Scandinavia.