Severe fluoropyrimidine toxicity in a patient with rectal adenocarcinoma with DPYD c.2846A>T heterozygous mutation: A case report.

Dihydropyrimidine dehydrogenase (DPD) is the key enzyme involved in fluoropyrimidine metabolism. Variants in the DPYD gene can lead to DPD deficiency, markedly increasing the risk of toxicity. The present report describes a case of a patient with rectal cancer treated with the CAPOX regimen (capecitabine and oxaliplatin) who developed grade 3 mucositis, fever, diarrhea and multi-organ dysfunction, necessitating prolonged intensive care unit support. The patient was managed with aggressive intravenous fluid therapy, a broad spectrum of antibiotics, antivirals and antifungal agents, extended use of granulocyte colony-stimulating factor and intensive anti-diarrheal treatment. Full clinical recovery was achieved, and the patient was discharged. Genetic analysis revealed a heterozygous c.2845A>T DPYD variant, known to be associated with fluoropyrimidine-related toxicity. The present case underscores the importance of early recognition of potential DPD deficiency and the essential role of prompt, intensive supportive care in managing severe fluoropyrimidine-related toxicities.