Acute hepatitis E, one of the causes of acute liver injury, has been increasingly diagnosed in developed countries in recent years. Misdiagnosis of acute hepatitis E virus (HEV) infection as drug-induced liver injury (DILI) may lead to discontinuation of effective chemotherapy. Thus, viral hepatitis, including hepatitis E, must be ruled out in the diagnosis of DILI. A 78-year-old woman with lung adenocarcinoma and multiple bone metastases received maintenance therapy with pemetrexed + pembrolizumab for a year. Increased aspartate aminotransferase and alanine aminotransferase levels, indicating acute liver injury, were observed. Initially, DILI was suspected, and she was given medications to lower the levels of hepatic enzymes. She was later admitted to the hospital with the chief complaint of general malaise and anorexia. Serum aspartate aminotransferase and alanine aminotransferase levels were markedly elevated (381 and 854 U/L, respectively). Acute HEV infection was diagnosed based on the detection of serum HEV immunoglobulin A antibodies. The patient received liver support therapy, and the serum hepatic enzymes recovered to normal levels. Chemotherapy was resumed without any subsequent relapse of hepatic enzyme elevation. When DILI is suspected during chemotherapy, exclusion of viral hepatitis is mandatory, which can be achieved by measuring markers of hepatitis viruses, including HEV, and examining the patient’s detailed medical history.

The Author(s). Published by S. Karger AG, Basel