A possible misdiagnosis in patients presenting with acute HBsAg-negative hepatitis: the role of hepatitis delta virus.

We describe here two cases of delta hepatitis (a coinfection and a superinfection) presenting as acute HBsAg-negative hepatitis. The first patient, a parenteral drug abuser, had a biphasic course of the disease, with HBsAg detectable transiently only during the relapse. Testing for delta markers on stored sera gave evidence of HBV/HDV coinfection. The other patient, a hospital nurse, chronic asymptomatic carrier of HBsAg, developed fulminant hepatitis with the transient appearance of antibody to HBsAg. She survived massive liver necrosis, and serological analysis of HDV markers documented a hepatitis delta virus superinfection. These cases demonstrate the possible substantial repression of HBV gene products exerted by the replication of delta virus, with a likely misdiagnosis if delta markers are not determined in serial serum samples.