[Dihydropyrimidine dehydrogenase deficiency causes severe adverse effects of capecitabine].

We report the case of a 61-year-old man who experienced severe adverse effects of capecitabine because of dihydropyrimidine dehydrogenase (DPD) deficiency. In 2016, he visited our hospital for adenocarcinoma of the gastroesophageal junction and was prescribed neoadjuvant chemotherapy with capecitabine, cisplatin, and trastuzumab. On day 14 of chemotherapy, he developed severe diarrhea, canker sores, enterocolitis, febrile neutropenia, and thrombocytopenia. He was then urgently hospitalized, and anticancer treatment was stopped. We administered antibiotics and G-CSF, and he gradually recovered. However, he complained of severe bloody stools due to hemorrhagic enteritis;hence, we performed a bowel resection. The level of DPD protein, which metabolizes 5-fluorouracil (FU), was very low (2.83U/mg). Therefore, he was diagnosed with DPD deficiency, based on DPD protein or urinary pyrimidine levels, which caused serious adverse effects of capecitabine. It is a rare condition, and 5-FU administration should be avoided in DPD deficiency cases.