P090 Is Epstein–Barr virus infection associated with the pathogenesis of microscopic colitis?

Abstract Background Epstein–Barr virus (EBV) has been associated with inflammation in the colon, particularly in patients with inflammatory bowel diseases, even if its potential impact on pathophysiology and course of the disease is still unclear. Conversely, no data are available on the association between EBV and microscopic colitis (MC). We aimed to compare the frequency of colonic EBV infection in patients with MC, ulcerative colitis (UC), and irritable bowel syndrome (IBS). Methods The frequency of colonic EBV infection in biopsies of 30 patients with MC, 30 patients with UC, and 30 controls with IBS was retrospectively assessed. PCR was performed to detect viral EBV DNA in colonic biopsies. In situ hybridisation was also performed to identify and localise EBV-encoded small RNAs (EBERs) within cells, which are known to play a role in inhibition of apoptosis, increase of cell proliferation, and induction of pro-inflammatory cytokines. Results The presence of EBV DNA was detected in 27 of 30 MC patients, in 20 of 30 UC cases, and in none of the IBS group. The frequency of EBV DNA in MC was significantly higher compared with that reported in UC (90.0% vs. 66.7%, p = 0.03). EBERs+ cells were observed in 18 of 30 MC patients (who also displayed the presence of EBV DNA), in only 3 of 30 UC patients (60.0% vs. 10.0%, p < 0.001), and in none of the IBS group. Clinical and histological characteristics of patients with microscopic colitis (MC), ulcerative colitis (UC), and irritable bowel syndrome (IBS). Variables MC (n = 30) UC (n = 30) IBS (n = 30) Mean age (range) 47 (20–78) 48.7 (17–88) 44.5 (20–64) Males 7 (23.3%) 15 (50.0%) 15 (50.0%) Collagenous/lymphocytic colitis 18 (60.0%)/12 (40.0%) Severe colitis 4 (14.3%) Colonic EBV-DNA + 27 (90.0%) 20 (66.7%) EBERs+ cells 18 (60.0%) 3 (10.0%) Figure 1. EBV in microscopic colitis. Conclusions This study shows for the first time that EBV infection is almost always detectable in patients with MC. The high frequency of EBERs+ cells observed in MC suggests that EBV may act deeper than as an innocent bystander, as it could play a causative role in the pathogenesis of the disease. Further studies are necessary to confirm this association and to clarify the role of EBV in MC and, more generally, in colonic inflammation.