Introduction: Hepatitis E is an emerging disease in developed countries with an increasing incidence. In developed countries, HEV genotype 3 prevails as a zoonotic disease carried by wild boars or pigs, which usually causes asymptomatic infection. Case Presentation: An asymptomatic HBsAg carrier was tested regularly at a German university hospital and showed no signs of chronic hepatitis B (CHB) activity. At a routine visit, elevated aminotransferases were detected while HBV DNA remained low and the patient was clinically asymptomatic. The laboratory signs of acute hepatitis resolved spontaneously. When aminotransferases returned to normal limits, the patient showed a flare of HBV-replication, which resolved spontaneously. In follow-up, further investigations revealed a resolved hepatitis E (HEV) superinfection causing an acute hepatitis before the HBV flare. No potential risk factors for HEV infection were identified. Conclusions: Elevated aminotransferases in CHB patients are most commonly caused by exacerbation of CHB. Nevertheless, when HBV DNA is not elevated, other reasons should be excluded. Amongst others, superinfection with another hepatotropic virus can be the reason for decompensation of chronic hepatitis B. This case report describes an asymptomatic HEV superinfection followed by a flare in HBV replication in an HBsAg carrier without signs of HBV replication for eight years. In CHB carriers with signs of acute hepatitis, rare causes should be considered as well. HEV should be a part of routine laboratory evaluation for hepatitis flares given the rising number of infections.
