A number of HLA associations have been described with the extra-intestinal manifestations of IBD. The majority of data has been derived from small studies from one single centre and should be interpreted with caution until replicated. Small sample size has also hindered attempts at determining the primary association, but the most convincing associations have been described with DRB1*0103[33] in mixed studies of ulcerative colitis and Crohn's disease. Type 1 peripheral arthritis, a migratory pauciarticular large joint arthritis has specifically been shown to be associated with HLA-DRB1*0103, as well as the class Ⅰ alleles that may be found in linkage disequilibrium, namely B*27 and B*35[33]. In this study, HLA-DRB1*0103 was found in 35% of patients compared to 3% of controls. In patients with recurrent arthritis this association becomes even stronger, being found in 65% of patients[33]. In contrast, type Ⅱ peripheral arthritis, a chronic, small joint, symmetrical arthritis is associated with HLA-B*44[33]. Uveitis has also been associated with DRB1*0103 and HLA-B*27, and erythema nodosum with the TNF promoter SNP TNF-1031C[34]. However, it is important to note that an increased prevalence of extra-intestinal manifestations has previously been reported in patients with colonic Crohn's disease[35] raising the possibility that the association between DRB1*0103 and the extra-intestinal manifestations may merely reflect the replicated association with colonic disease. Further work is required to clarify this issue.
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