Abstract
All-trans-retinoic acid (ATRA) is a new and effective treatment of acute promyelocytic leukemia. It has many side-effects, including the retinoic acid syndrome and Sweet's syndrome. There have been only nine cases of hypercalcemia associated with ATRA described in the literature. We discuss a case of hypercalcemia, which we believe was due to inhibition of cytochrome P450 function by voriconizole when used concomitantly with ATRA.