Therapy of occult hepatitis B virus infection and prevention of reactivation.

Occult HBV infection (OBI) is highly prevalent worldwide. In some cases, it is a consequence of infection with variant viruses mutated in the S gene and producing a surface antigen not recognized by diagnostic kits. In most cases, OBI is due to a strong inhibition of HBV activities exerted by host defense mechanisms. OBI may reactivate in patients undergoing immunosuppressive- and/or chemo-therapies with possible, consequent development of acute hepatitis that may lead to hepatic failure. Hematological malignancies and Rituximab-included therapeutic schedules are the conditions most frequently associated with OBI reactivation. However, this event may occur in a quite large number of additional clinical and therapeutic settings. Identification of patients prone to undergo reactivation is of great importance for promptly starting a proper anti-viral therapy that may stop the HBV reactivation and may prevent its clinical sequels.