Acute lymphoblastic leukemia maintenance chemotherapy includes mercaptopurine, a purine analog with uncommon side effects, that can be life-threatening. We describe a 7-year-old female patient with ALL that presented with altered state of consciousness after maintenance chemotherapy with methotrexate and 6-mercaptopurine, due to severe hypoglycemia with metabolic acidosis. She initiated metabolic corrections with rapid resolution of symptoms. Hypoglycemia secondary to 6-mercaptopurine is a rare and transient side effect. The cause effect relation is difficult to establish, leading to underdiagnosis. Hypoglycemia is preventable without compromising maintenance therapy efficacy.
Keywords: Hypoglycemia; acute lymphoblastic leukemia; mercaptopurine.