Dihydropyrimidine dehydrogenase deficiency

Dihydropyrimidine dehydrogenase deficiency is an inherited metabolic disorder in which the body lacks working dihydropyrimidine dehydrogenase, an enzyme that helps break down the pyrimidines uracil and thymine. It varies widely in severity. In its severe form it shows in infancy with neurological problems such as seizures, intellectual disability, a small head, raised muscle tone, delayed motor development and autistic behaviours, while other affected people have no symptoms and are found only by laboratory testing. Even people without symptoms are at risk of dangerous toxic reactions to fluoropyrimidine cancer drugs such as 5-fluorouracil and capecitabine, because the same enzyme normally clears them from the body. The condition is caused by variants in the DPYD gene and is inherited in an autosomal recessive pattern.