Severe fluoropyrimidine toxicity in a patient with rectal adenocarcinoma with <i>DPYD</i> c.2846A&gt;T heterozygous mutation: A case report

Dihydropyrimidine dehydrogenase (DPD) is the key enzyme involved in fluoropyrimidine metabolism. Variants in the <i>DPYD</i> 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 <i>DPYD</i> 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.