First Reported Case of Upadacitinib-Associated Cytomegalovirus Viremia and Suspected Pneumonitis in Ulcerative Colitis

Cytomegalovirus (CMV) reactivation is a clinically important risk in patients with inflammatory bowel disease, particularly those receiving systemic immunosuppression or Janus kinase (JAK) inhibitor therapy, which can impair immunity. JAK inhibitors, including upadacitinib, may predispose patients to opportunistic viral infections. We report a patient with moderate ulcerative colitis who developed CMV viremia with suspected CMV pneumonitis 4 weeks after starting upadacitinib. Antiviral therapy led to clinical and virologic resolution. This case broadens the spectrum of CMV-related complications associated with JAK inhibition and underscores the importance of maintaining vigilance for systemic viral reactivation in inflammatory bowel disease patients receiving immunosuppressive therapy.