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

•The frequency of EBV infection in microscopic colitis (MC) is unknown.•EBV infection was almost always detectable in the colonic mucosa of our MC patients.•The role – active or passive? – of EBV in MC is still unclear. Epstein-Barr virus (EBV) has been associated with inflammation in the colon, particularly in patients with inflammatory bowel disease (IBD). Even if a relevant plasmocytosis, similar to IBD, is present in microscopic colitis (MC), the frequency of EBV infection in this setting is unknown. We aimed to compare the frequency of colonic EBV infection in patients with MC, ulcerative colitis (UC), and irritable bowel syndrome (IBS). 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 hybridization was also performed to identify and localize EBV-encoded small RNA1 and 2 (EBERs) within cells. The presence of EBV DNA was detected in 27 out of 30 MC patients, in 20 out of 30 UC cases, and in none of 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 out of 30 MC patients, in only 3 out of 30 UC patients (60.0% vs. 10.0%, p