Concurrent cytomegalovirus enteritis and atypical hemolytic uremic syndrome with gastrointestinal tract involvement: a case report.

Atypical hemolytic uremic syndrome (aHUS) is a rare disease caused by complement dysregulation that may involve the extra-renal system. Without appropriate prophylactic treatment, aHUS commonly recur after kidney transplantation (KT). In contrast, cytomegalovirus (CMV) infection is common in KT recipients and may affect various organ systems. Herein, we report a case of recurrent aHUS complicated by CMV enteritis. This 17-year-old KT recipient with aHUS having a CFH mutation was admitted to the hospital for gastric pain and vomiting. With worsening hemogram, recurrence of aHUS involving the gastrointestinal (GI) system was suspected. Upon treatment with anti-C5 antibody, the patient's blood counts soon improved, but her GI symptoms did not. Esophagogastroduodenoscopy revealed multiple ulcers in the duodenum with pathologic findings consistent with aHUS and CMV enteritis; however, she did not have CMV antigenemia despite these findings. Treatment with ganciclovir resolved GI symptoms within 7 days. This case shows that recurrence of aHUS is often induced by intercurrent infection, and common infections after allograft transplantation, such as CMV, should always be suspected and confirmed for a proper treatment, particularly because CMV enteritis may not accompany CMV antigenemia.