Cytomegalovirus infection and inflammatory bowel disease

Abstract

Introdction: Inflammatory bowel disease (IBD) is a general name of two entities: Crohn's disease (CD) and ulcerative colitis (UC) which represent chronic non-specific inflammation of gastrointestinal tract. The etiology of IBD is not clear and Cytomegalovirus infection is often associated with IBD. The pathogenetic link between IBD and CMV infection was supposed and began to be studied in the last decades. Purpose and objectives: The aim of the study was to evaluate critically literature data on the relationship between CMV and IBD. Materials and methods: Internet search was conducted in Medline (from 1966 to2013) and PubMed (from 1980 to 2013) database using words “cytomegalovirus”, “inflammatory bowel disease”, “ulcerative colitis”, “Crohn's disease”. Results: 419 articles were found. Early studies indicated that CMV infection can lead to subsequent development of IBD. But in the more recent studies was demonstrated that CMV colitis occurred primarily in patients with pre-existing IBD. There have also been reports of colitis patients with evidence of active CMV infection who improved with steroids and did not require antiviral treatment, as well as patients with active colonic CMV infection without active colitis. In these cases CMV seems to behave like an innocent bystander. CMV has the propensity to infect rapidly growing tissue, especially endothelial cells in granulation tissue. Some studies suggested that CMV represents an opportunistic infection in severely inflamed mucosa rather than a primary pathogen. The most widely held theory is that CMV infects areas o f active IBD and causes further tissue injury aggravating the severity of the underlying IBD. In the majority of case-reports patients with severe attacks of IBD and CMV infection had significant morbidity (toxic megacolon 15%, colectomy up to 62%) and mortality (up to 44%). Antiviral treatment prevented colectomy in some but not all of the patients. In more recent series the morbidity of CMV colitis in UC were 30% and the rate of surgery 40%. CMV disease seems to be less frequent in patients with CD compared to patients with UC. The prevalence of CMV infection in steroid-refractory IBD patients, in 2 studies, was 36% and 33%, respectively. Conclusion: The role of CMV infection in patients with IBD has not yet been clearly defined. In the majority of published studies CM V is considered as pathogenetic factor, which complicates the IBD course causing the resistance, while in others CMV does not seem to alter the natural course of the underlying IBD.