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DPYD gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

DPYD gene

The DPYD gene provides instructions for an enzyme that breaks down pyrimidines, which are essential building blocks of DNA and RNA.

Overview

The DPYD gene provides instructions for making the enzyme dihydropyrimidine dehydrogenase. This enzyme is responsible for the first step in breaking down uracil and thymine, which are pyrimidines—the building blocks of DNA, RNA, and energy-carrying molecules like ATP and GTP.

The enzyme converts uracil to 5,6-dihydrouracil and thymine to 5,6-dihydrothymine. These breakdown products are either excreted or repurposed in other cellular processes.

Health Conditions Related to Genetic Changes

Dihydropyrimidine dehydrogenase deficiency

Mutations in the DPYD gene lead to dihydropyrimidine dehydrogenase deficiency. This condition interferes with the breakdown of uracil and thymine, causing these molecules to accumulate in the blood, urine, and cerebrospinal fluid.

  • The accumulation of uracil and thymine is associated with various neurological problems.
  • The deficiency also impairs the body's ability to break down certain drugs, such as the cancer treatments 5-fluorouracil and capecitabine.
  • Because these drugs are structurally similar to pyrimidines, they accumulate in the body, leading to severe, potentially toxic reactions in affected individuals.

Genomic Location

The DPYD gene is found on chromosome 1.

Frequently Asked Questions

You can still be treated, but the regimen must be modified. Options include a substantial dose reduction of 5‑FU/capecitabine (often 25‑50 % of the standard dose), using a different class of chemotherapy that does not rely on pyrimidine metabolism, or adding supportive measures such as leucovorin rescue. The exact plan should be individualized by a pharmacogenomics‑aware oncologist.
Watch for sudden onset of mouth sores, severe diarrhea, nausea/vomiting, fever, neutropenia (low white‑blood‑cell count), or unexpected fatigue within the first 1–2 weeks of treatment. If any of these appear, contact your oncology team immediately; prompt dose reduction or drug discontinuation can prevent organ damage.
Most clinically relevant DPYD loss‑of‑function variants are inherited in an autosomal‑recessive manner, meaning a person needs two defective copies to have complete deficiency, but carriers (one copy) can still experience increased toxicity. First‑degree relatives are advised to undergo DPYD testing, especially if they may receive fluoropyrimidine chemotherapy, to guide safe dosing.
Yes. International oncology guidelines recommend DPYD genotyping or phenotyping (uracil plasma level) before initiating 5‑FU‑based regimens because certain DPYD variants dramatically increase the risk of life‑threatening toxicity. Testing allows the oncologist to adjust the dose or choose an alternative drug up front.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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