Herpes zoster during treatment with arsenic trioxide.

In vitro data suggest that arsenic compounds can suppress cell-mediated immunity by inducing apoptosis of T helper lymphocytes. We describe an occurrence of herpes zoster during treatment with arsenic trioxide (ATO) in two patients who were already in remission from acute promyelocytic leukemia and received ATO as consolidation treatment. During this complication, their leukocyte counts and differentials were within normal limits. Our report suggested the immunosuppressive effect of ATO in vivo. Both patients responded well to an oral antiviral. Clinicians should be aware of this complication during treatment with ATO since early antiviral treatment may help avoid complications including post-herpetic neuralgia.