[Severe toxicity after treatment with capecitabine and fluorouracil due to partial dihydropyrimidine dehydrogenase deficiency]

Two female patients, aged 48 and 52 years, developed severe bone marrow suppression and (gastrointestinal) mucositis following administration of capecitabine. Analysis of the dihydropyrimidine dehydrogenase (DPD) activity in peripheral blood mononuclear cells revealed the presence of DPD deficiency. Both patients recovered in 3-4 weeks, and both had a (partial) remission of their tumours. Capecitabine is metabolised to 5-fluorouracil (5-FU) in the body. DPD-deficiency leads to impaired breakdown of 5-FU and hence to severe cytotoxicity following treatment with capecitabine or 5-FU. The most common mutation, IVS14 + 1G > A, is found in approximately 2% of the Dutch population. In case of unexpected severe toxicity during 5-FU or capecitabine treatment, DPD deficiency should be considered. Screening could be considered in view of the widespread use of capecitabine and 5-FU, the severe toxicity that may develop in patients with low DPD activity and the prevalence of the mutation.

Dehydropyrimidine dehydrogenase deficiency in a cancer patient undergoing 5-fluorouracil chemotherapy

We present a case of a Caucasian cancer patient undergoing 5-fluorouracil (5-FU)-containing chemotherapy in our department. The 49-year-old female patient suffered from adverse effects representing WHO grade 3 toxicity. Genotyping revealed that she carried the exon 14-skipping mutation which is known to result in dehydropyrimidine dehydrogenase (DPD) deficiency. DPD is the enzyme that converts 5-FU to inactive metabolites and therefore dictates the amount of 5-FU that is available to be metabolised to cytotoxic nucleotides. Consequently DPD deficiency is the cause of severe adverse and sometimes lethal reactions to 5-FU. In conclusion the identification of cancer patients at increased risk of severe toxicity prior to the administration of 5-FU would be desirable.

Head imaging abnormalities in dihydropyrimidine dehydrogenase deficiency

Dihydropyrimidine dehydrogenase (DPD) deficiency is a rare autosomal recessive disorder of pyrimidine metabolism. Patients may present with a wide range of neurological symptoms during the first years of life. Head imaging abnormalities have been reported only rarely and include diffuse cerebral atrophy and white-matter hyperintensity. The pathogenesis of the white-matter abnormalities is unknown, although environmental factors and altered energy metabolism may be involved. To further understanding of the spectrum of brain abnormalities associated with DPD deficiency, we report a 17-month-old girl, born to a consanguineous Pakistani couple, who had a history of encephalopathy, prolonged hypoventilation, developmental delay and failure to thrive. Head MRI showed prominent sulci and abnormal T2 prolongation in the cerebral white matter and brainstem. Thus, DPD deficiency may feature prominent brain abnormalities involving the cerebral white matter and brainstem. Anoxic stress may have contributed to the clinical presentation and brain findings in this case. In order to define more clearly the contribution of DPD deficiency to the pathogenesis of these MRI abnormalities, we recommend performing detailed analysis of urine pyrimidine metabolites in patients who have such findings.

Denaturing high performance liquid chromatography analysis of the DPYD gene in patients with lethal 5-fluorouracil toxicity

Dihydropyrimidine dehydrogenase (DPD) enzyme deficiency is a pharmacogenetic syndrome with possible fatal outcome following 5-fluorouracil (5-FU) treatment. Several studies examining the molecular basis for DPD deficiency have identified over 30 sequence variations in the DPYD gene (which codes for the DPD enzyme). Our laboratory has recently developed and validated a denaturing high performance liquid chromatography method capable of identifying both known and unknown sequence variations in the DPYD gene. In the present study, we used this denaturing high performance liquid chromatography approach to examine the DPYD genotype of three patients who experienced lethal toxicity after administration of 5-FU. DPD enzyme activity could only be measured in one patient before death and demonstrated that lethal toxicity can occur in a partially DPD-deficient individual. Multiple heterozygous sequence variations (both known and unknown) were detected in all three patients including the novel variants 545T>A, M182K and 2329G>T, A777S. We conclude that (a) lethal toxicity can occur in partially DPD-deficient individuals after administration of 5-FU and is not exclusive to profoundly DPD-deficient individuals as suggested previously, (b) the complicated heterozygote genotype seen in these patients, combined with DPD deficiency being an autosomal codominant inherited syndrome, precludes the use of simple genotyping assays that identify only one or two mutations as a method for identifying DPD-deficient individuals; and (c) these multiple heterozygote genotypes (which are more difficult to accurately characterize) may be responsible for some of the conflicting reports which suggests a lack of correlation between phenotype and genotype.

Impact of dihydropyrimidine dehydrogenase on 5-fluorouracil treatment in cancer patients

The aim of the study is the identification of cancer patients at increased risk for severe toxicity prior to the administration of 5-FU.

Dihydropyrimidine dehydrogenase deficiency and acute neurological presentation

Dihydropyrimidine dehydrogenase (DPD) deficiency has been linked to 5-fluorouracil toxicity, but patients may present a wide clinical spectrum. We describe a 1-year-old Tunisian girl with a dramatic onset of neurological symptoms suggesting the possible triggering role of environmental factors.

Possible prediction of adverse reactions to fluorouracil by the measurement of urinary dihydrothymine and thymine

Dihydropyrimidine dehydrogenase (DPD) deficiency with a defect of the pyrimidine catabolic pathway has recently become the focus of considerable attention, due to the severe 5-fluorouracil (5-FU) toxicities occurring in DPD deficiency patients. Studies also suggest that 5-FU toxicities could occur in another pyrimidine metabolic disorder, dihydropyrimidinuria (DHPuria). This study shows that urinary dihydrothymine (DHT) and thymine (THY) are useful indexes for detection of DPD deficiency and DHPuria. We measured urinary DHT and THY in 276 Japanese adults to establish reference ranges. When males and females were compared, both DHT and THY levels were found to be significantly higher in females. The reference ranges (mean +/- SD with logarithmic values) for males were found to be 1.56-5.70 micromol/g of creatinine for DHT and 0.40-1.47 micromol/g of creatinine for THY. The reference ranges for females were found to be 1.89-8.33 micromol/g of creatinine for DHT and 0.58-2.30 micromol/g of creatinine for THY. In addition to this study we analyzed a DPD deficiency case and a DHPuria case. In the DPD deficiency case, the THY concentrations of all urine samples were out of the reference range. However, uracil levels in most of the samples were within the normal range. The DHPuria case excreted large amounts of DHT and dihydrouracil, both out of the normal range.