Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.

Diseases

Genetic and Rare Diseases Information Center (GARD)

Print friendly version

Dihydropyrimidine dehydrogenase deficiency


Other Names for this Disease
  • DPD deficiency
  • Familial pyrimidinemia
  • Hereditary thymine-uraciluria
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Overview



What is dihydropyrimidine dehydrogenase (DPD) deficiency?

What causes dihydropyrimidine dehydrogenase (DPD) deficiency?

How is dihydropyrimidine dehydrogenase deficiency inherited?

How is dihydropyrimidine dehydrogenase (DPD) deficiency diagnosed?


What is dihydropyrimidine dehydrogenase (DPD) deficiency?

Dihydropyrimidine dehydrogenase (DPD) deficiency is a condition in which the body cannot break down the nucleotides thymine and uracil. DPD deficiency can have a wide range of severity; some individuals may have various neurological problems, while others have no signs and symptoms. Signs and symptoms in severely affected individuals begin in infancy and may include seizures, intellectual disability, microcephaly, increased muscle tone (hypertonia), delayed motor skills, and autistic behavior.[1]  All individuals with the condition, regardless of the presence or severity of symptoms, are at risk for severe, toxic reactions to drugs called fluoropyrimidines which are used to treat cancer. Individuals with no symptoms may be diagnosed only by laboratory testing or after exposure to fluoropyrimidines. DPD deficiency is caused by mutations in the DPYD gene and is inherited in an autosomal recessive manner.[1]
Last updated: 8/20/2012

What causes dihydropyrimidine dehydrogenase (DPD) deficiency?

DPD deficiency is caused by mutations in the DPYD gene. This gene provides instructions for making an enzyme called dihydropyrimidine dehydrogenase (DPD), which is involved in the breakdown of molecules called uracil and thymine. Uracil and thymine are building blocks of DNA, RNA, and molecules that serve as energy sources in cells.

Mutations in the DPYD gene result in deficiencies (to various degrees) of functional DPD, interfering with the breakdown of uracil and thymine in cells. This results in excessive amounts of uracil and thymine in the blood, urine, and the fluid that surrounds the brain and spinal cord. It is currently poorly understood exactly how this cascade of events causes the signs and symptoms of the condition.[1]
Last updated: 8/20/2012

How is dihydropyrimidine dehydrogenase deficiency inherited?

Dihydropyrimidine dehydrogenase (DPD) deficiency is inherited in an autosomal recessive manner. This means that in affected individuals, both copies of the DPYD gene in each cell (one inherited from each parent) have mutations. The mutations that cause DPD deficiency vary widely in severity; therefore, some people with 2 mutated copies of the gene may have signs and symptoms of the condition, while others may be asymptomatic. However, all individuals with 2 mutations are at risk for toxic reactions to fluoropyrimidine drugs.[1]

Individuals who carry one mutated copy of the disease-causing gene (including most parents of affected individuals) are referred to as carriers. Carriers typically do not have signs and symptoms of the condition. However, people with one mutated copy of the DPYD gene may still experience toxic reactions to fluoropyrimidine drugs.[1]

When 2 carriers for the same autosomal recessive condition have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each parent, and a 25% risk to not have the condition and not be a carrier. A child of one carrier parent has a 50% risk to also be a carrier.
Last updated: 8/20/2012

How is dihydropyrimidine dehydrogenase (DPD) deficiency diagnosed?

DPD deficiency may be diagnosed in various ways. In individuals with complete or profound DPD deficiency, laboratory testing can detect elevated levels of uracil and/or thymine in plasma or urine. Partial DPD deficiency is more difficult to detect, which has led to the development of a radioenzymatic test for the DPD enzyme. This test has remained the gold standard for diagnosing DPD deficiency even after the development of genetic testing for the condition, because of the complexity of the DPYD gene and the presence of multiple DNA sequence variations present in most affected individuals. Various types of cells and tissues can be examined this way.[2] More recently, a rapid, noninvasive, and cost-effective breath test was developed. This test permits the evaluation of DPD activity (normal activity and partial or profound deficiency) before the administration of fluoropyrmidine drugs such as 5-FU.[2]
Last updated: 8/20/2012

References
  1. Dihydropyrimidine dehydrogenase deficiency. Genetics Home Reference. November 2011; http://ghr.nlm.nih.gov/condition/dihydropyrimidine-dehydrogenase-deficiency. Accessed 11/28/2012.
  2. Ezzeldin H, Diasio R. Dihydropyrimidine dehydrogenase deficiency, a pharmacogenetic syndrome associated with potentially life-threatening toxicity following 5-fluorouracil administration. Clin Colorectal Cancer. September 2004; 4(3):181-189.