A 22-year-old black male was given the antimalaria drug primaquine to take while on an expedition on the Amazon River. After taking the drug, he developed an acute anemia. The anemia was secondary to an intravascular hemolytic crisis. This crisis was reversed when he discontinued taking the primaquine. This drug-induced hemolytic anemia arises in persons who have a deficienc in which of the following enzymes?

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The hemolytic anemia is due to a deficiency in glucose-6-phosphate dehydrogenase (G6PD), which is crucial for protecting red blood cells from oxidative damage. Primaquine can induce oxidative stress, leading to hemolysis in individuals with G6PD deficiency. Primaquine is used to treat malaria since it causes lysis of erythrocytes that have been weakened by the presence of the parasite. When administered to humans, primaquine is metabolized into an arylhydroxylamine metabolite that exerts the hemotoxi effects. Primaquine causes methemoglobinemia in all patients. However, dangerous levels of methemoglobinemia only occur in patients with G6PDH deficiency and, thus, this drug should not be administered to anyone with a deficiency of this enzyme

A 22-Year-Old Black Male Was Given the Antimalaria Drug Primaquine