Feld – Advisory Committees or Review Panels: Idenix, Merck, Janssen, Gilead, selleck chemicals AbbVie, Merck, Theravance, Bristol Meiers Squibb; Grant/Research Support: AbbVie, Boehringer Ingelheim, Janssen, Gilead, Merck The following people have nothing to disclose: Angela C. Cheung, Javier M. Meza-Cardona, Matthew Kowgier Background & Aims: It has been postulated that primary sclerosing cholangitis (PSC) develops through immune mediated mechanisms triggered by complex gene-environment interactions in susceptible individuals. However, the relationships between PSC and the environment are largely unknown. While

tobacco use has been reported to have a negative association with PSC, other exposures particularly dietary habits and methods of food preparation have not been well explored. Our aims were to validate or refute associations reported in previous studies

and to identify novel environmental exposures among PSC patients. Methods: We performed a case-control analysis utilizing self-administered questionnaires. Cases were recruited from 8 academic medical centers across North America and controls were recruited from the Mayo Clinic during annual visits for preventive health care. Responses between cases (n=1000) and controls (n=663) were compared using multivariable logistic regression adjusted for age and gender. The model was further stratified based on inflammatory bowel disease (IBD) status (with IBD n=741; without IBD n=259). Results: A history of smoking was

inversely associated with PSC only when IBD was present (OR, 0.5; 95% CI 0.4-0.7) PXD101 but not among PSC patients without IBD (OR, 0.9; 95% CI 0.7-1.2). Moreover, women with PSC (irrespective of the presence of IBD) were less likely to have received hormone replacement therapy (HRT) (OR, 0.5; 95% CI 0.4-0.7) and were more likely to have recurrent urinary tract infections (UTI’s) (OR, 1.6; 95% CI 1.2-2.3) when compared to controls. Furthermore, PSC patients regardless of gender or IBD status were less likely to eat fish (OR, 0.4; 95% CI 0.3-0.6), vegetables (OR, 0.9; 95% CI 0.8-0.9) and grilled/barbecued meat MCE (OR, 0.8; 95% CI 0.7-0.9). In contrast, PSC patients with and without IBD were more likely to consume steak/burgers that were more well-done (OR, 1.3; 95% CI 1.2-1.5). Conclusions: To date, this is the largest study (which represents approximately 3% of the estimated PSC patient population in the United States) that examines environmental exposures and PSC. IBD (rather than PSC) was associated with smoking. Women with PSC were more likely to have recurrent UTI’s and less likely to receive HRT. Furthermore, dietary intake and methods of food preparation differs in PSC patients when compared to controls. Estrogen, recurrent UTI’s and dietary habits may be relevant to the pathogenesis of PSC and warrant further study.