[Reactivation of hepatitis B following withdrawal of chloroquine]

A severe flare-up of chronic hepatitis B infection with liver cell insufficiency has been observed in two patients after discontinuation of chloroquine administered either as malaria prophylaxis or as treatment of presumed rheumatoid arthritis. Chloroquine is known to inhibit the association of the major histocompatibility complex type II with hepatitis B virus antigens, thereby inhibiting T-cell mediated lysis of infected cells. Furthermore, it inhibits uptake of duck hepatitis B virus by duck liver cells. These in vitro studies and our clinical observations suggest that chloroquine inhibits the lysis of hepatitis B virus infected hepatocytes. Withdrawal of chloroquine in patients with chronic hepatitis B virus infection can lead to a rebound immune response manifesting as a reactivation of hepatitis B, similar to that observed after steroid withdrawal.