An Unusual Case of Gastritis in One Patient Receiving PD-1 Blocking Therapy: Coexisting Immune-Related Gastritis and Cytomegaloviral Infection

The programmed death 1 (PD-1), programmed death ligand 1 (PD-L1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) immune checkpoints are negative regulators of T-cell immune function. Inhibition of these targets by antibodies (PD-1 blocking therapy) has been explored to treat solid malignancies such as melanoma, non-small cell lung cancer and other cancers. PD-1 blocking therapy is known to cause gastrointestinal tract adverse events in some patients and some of the adverse events are thought to be immune-mediated. Cancer patients receiving PD-1 blocking therapy have often failed several lines of chemotherapy and thus potentially are susceptible to a variety of infections including cytomegaloviral infection. However, there has not been any report of concurrent immune-mediated gastroenterocolitis and cytomegaloviral infection in cancer patients receiving PD-1 blocking therapy. Herein, we report one unusual case of histologically confirmed gastritis with features of immune-mediated pangastritis and cytomegaloviral infection in one patient who had metastatic urothelial carcinoma and received PD-1 blocking therapy, initially with atezolizumab (anti-PD-L1 antibody) followed by a switch to pembrolizumab (anti-PD-1 antibody) because of tumor progression. Pembrolizumab was held and intravenous ganciclovir treatment was started, the patient's symptoms (abdominal pain and vomiting) were significantly improved and she was discharged from the hospital in stable conditions on hospital day 5. Pathologists should be aware of PD-1 blocking therapy-associated immune-mediated gastrointestinal tract adverse effect and concurrent cytomegaloviral infection.