The genetic variation in drug metabolism pathway that results in severe toxicity of fluorouracil is:
Genetic variation in drug metabolism pathway dihydropyrimidine dehydrogenase results in severe toxicity of capecitabine, fluorouracil. Ref: Harrison, Edition-18, Page-42.
CYP2C9
Dihydropyrimidine dehydrogenase
Thiopurine-S methyltransferase
CYP2D6