DPYD and Gait ataxia: Dihydropyrimidine dehydrogenase (DPYD) deficiency, which interferes with 5‐FU catabolism, has been associated with 5‐FU‐induced neurotoxicity manifesting as gait ataxia, confusion, stupor, and even coma.8, 9 However, DPYD enzymatic activity was normal (Figure 2B), and the common mutations, DPYD*2A (IVS14 +1 G>A) and DPYD*13 (1679T>G; I560S), were absent.