Dihydropyrimidine Dehydrogenase Deficiency: Causes, Symptoms, and Treatment
Medically reviewed by Harsha Moole, MD, Internal Medicine. Last reviewed: October 2, 2026.
What kind of doctor treats Dihydropyrimidine Dehydrogenase Deficiency?
A primary care doctor can order testing and explain results. The cancer care team, usually led by a medical oncologist, makes decisions about cancer drugs. People with the rare nervous system form may also see a neurologist. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is Dihydropyrimidine Dehydrogenase Deficiency?
Dihydropyrimidine dehydrogenase deficiency, often called DPD deficiency, is a condition where the body lacks enough of an enzyme that breaks down certain building blocks of cells. Without it, a cancer drug called fluorouracil can build up and cause severe side effects. Some people have no symptoms until they receive this drug.
Dihydropyrimidine dehydrogenase is an enzyme that breaks down pyrimidines, parts of DNA. People with DPD deficiency make little or none of it. This matters most during cancer treatment: fluorouracil and capecitabine depend on this enzyme to leave the body, and without it these drugs build up and cause serious harm.
Symptoms
Most people have no symptoms in everyday life. Problems appear after taking fluorouracil or capecitabine, causing severe diarrhea, mouth sores, nausea, vomiting, low blood counts, and sometimes dangerous infections. A rare childhood form can cause seizures and developmental delays.
Causes and who gets it
DPD deficiency is caused by mutations in the DPYD gene and is passed down from parents to children. Partial DPD deficiency is fairly common, affecting a few people in every 100, while complete deficiency is much rarer, and many people do not know they have it.
How doctors diagnose it
Doctors can test before giving fluorouracil or capecitabine. The most common test looks for DPYD gene changes; another measures enzyme activity in a blood sample.
Treatment
There is no cure, but many people never need treatment. The main step is avoiding fluorouracil and capecitabine, or using a much lower dose with close monitoring if a specialist decides the benefit is worth it. If severe side effects happen, hospital care and a drug called uridine triacetate can help clear fluorouracil from the body.
When to see a doctor
Tell your doctor right away if you develop severe diarrhea, vomiting, mouth sores, fever, or unusual tiredness while receiving fluorouracil or capecitabine; these need urgent care. Also talk to a doctor before cancer treatment if a family member has it.
How a direct primary care or concierge doctor fits in
A direct primary care doctor is paid a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Either can be a helpful partner, offering longer visits and easier access for coordinating testing or explaining results, and they refer to an oncologist or neurologist when needed.
Common questions
Is DPD deficiency the same as being allergic to chemotherapy?
No. It is not an allergy. The body cannot break down certain drugs quickly, so they stay longer and cause stronger effects.
Can I have DPD deficiency and never know it?
Yes. Many people feel fine their whole lives; the problem usually appears only after taking a fluorouracil-based cancer drug.
Should my family members get tested if I have it?
Because it is inherited, close family members may carry the same gene change. Many doctors suggest genetic counseling to help family members decide about testing.
Does DPD deficiency mean I cannot be treated for cancer?
No. Many cancer drugs do not depend on this enzyme, and a specialist can choose a safe treatment plan.
Sources
- NIH Genetic and Rare Diseases Information Center - Dihydropyrimidine dehydrogenase deficiency
- MedlinePlus Genetics - Dihydropyrimidine dehydrogenase deficiency
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
