Appendectomy, other abdominal surgeries, and tonsillectomy were significantly more frequently reported in patients with PBC in an epidemiological study in North America [155] . However, an earlier population-based case control study conducted in England did not show such associations [156] . More recently, another case-control study provided evidence that there was at least no association between PBC and the occurrence of appendectomy and pointed out the selection bias present in the previous study done in North America [157] . The linkage to appendectomy was theoretically attractive, since a PBC-specific immune response to the highly conserved caseinolytic protease P of Yersinia enterocolitica in 40% of patients with PBC was reported [158] . It is noteworthy, that infection with Y. enterocolitica is one of the major causes of acute terminal ileitis mimicking acute appendicitis [159] .