Background and aims: Steroid-resistance presents a management challenge in ulcerative colitis. How steroid-resistance occurs is unknown, but cytomegalovirus infection, often unrecognised, may be the cause in some patients. Current evidence and therapeutic recommendations are examined.
Methods: A systematic review of PubMed and EMBASE databases was performed. Search and exclusion criteria are defined in the text.
Results: Heterogeneity of experimental design and definitions of key terms were notable. Criteria for cytomegalovirus disease, infection or detection varied, as did definitions of steroid-resistance. CMV infection defined by antigenaemia or serology was common in patients on steroids and associated with a higher rate of steroid-resistance (41.66-61% versus 0-68% in steroid-responsive patients). Colonic mucosal cytomegalovirus disease detected by histopathology was associated with intravenous steroid-resistance in 5-36%, compared to 0-10% of steroid-responsive patients. CMV colitis has rarely been reported in association with ulcerative colitis without steroids or other immunomodulators. CMV colitis in healthy individuals is so exceptional as to be the topic of case reports.
Conclusion: Ulcerative colitis and its treatment put patients at risk of CMV infection or reactivation. A distinction is necessary between CMV disease (colitis) and CMV infection. Only colonic mucosal CMV infection detected by histopathology appears clinically relevant and appropriate for antiviral therapy. CMV antigenaemia may be associated with steroid-resistance, but may also be a self-limiting marker of viral reactivation. The impact of CMV on steroid-resistance is complicated by inconsistencies in the literature. Coherent definitions of clinically relevant CMV infection and steroid-resistance are needed.