On day 28 of hospitalization a second phenotyping test (at a distance from capecitabine administration and interference by competitive inhibition of the DPD enzyme) was reported to be compatible with a complete DPD deficiency, which was in line with the clinical situation of our patient (U: 64.9 ng/mL; UH2: 54.4 ng/mL; UH2/U: 0.8). This evidence concerns the gene DPYD and dihydropyrimidine dehydrogenase deficiency.