Arsenic trioxide has been steadily used as a treatment for acute promyelocytic leukemia over the decade. Peripheral neuropathy is a common complication of arsenic therapy and the symptoms are usually mild and reversible following discontinuation of the therapy. However, the clinical course of arsenic neurotoxicity in patient with coexistence of thiamin deficiency may potentially lead to be severe weakness and bad prognosis. It is important to determine the serum thiamine level of patients with acute promyelocytic leukemia before administrating Arsenic trioxide
