Three different polymorphisms of the DPYD gene associated with severe toxicity following administration of 5-FU: a case report

BACKGROUND: Dihydropyrimidine dehydrogenase deficiency secondary to polymorphisms in the DPYD gene can lead to significant toxicity associated with the administration of fluoropyrimidine chemotherapy. CASE PRESENTATION: We report a case of a 59-year-old Lebanese woman with metastatic pancreatic cancer who received FOLFIRINOX therapy and developed severe 5-fluorouracil toxicity after a single cycle. The entire DPYD gene was sequenced, and the patient was found to be heterozygous for three different polymorphisms that have reportedly been associated with dihydropyrimidine dehydrogenase deficiency. CONCLUSION: Because data regarding the prevalence and clinical significance of several heterozygous polymorphisms in a single DPYD gene are very limited, we suggest that full gene sequencing should be carried out, at least in populations in which the allele frequencies are unknown.