Inborn Errors of Metabolism with Hyperammonemia: Urea Cycle Defects and Related Disorders

Pediatr Clin North Am. 2018 Apr;65(2):231-246. doi: 10.1016/j.pcl.2017.11.004. Epub 2018 Feb 2.


The urea cycle disorders are a group of inherited biochemical diseases caused by a complete or partial deficiency of any one of the enzymes or transport proteins required to convert toxic ammonia into urea and to produce arginine and citrulline. The clinical manifestations of these disorders are mostly the result of acute or chronic hyperammonemia, which affects the central nervous system. Affected individuals can also develop hepatic dysfunction. These disorders can present at any age from the immediate newborn to later in life. Early diagnosis and treatment are key to improving outcomes.

Keywords: Ammonia; Arginine; Citrulline; Hyperammonemia; Liver; Ornithine; Urea cycle.

Publication types

  • Review

MeSH terms

  • Ammonia / blood
  • Emergency Treatment / methods
  • Humans
  • Hyperammonemia / diagnosis*
  • Hyperammonemia / etiology
  • Hyperammonemia / therapy
  • Infant
  • Infant, Newborn
  • Urea / metabolism
  • Urea Cycle Disorders, Inborn / diagnosis*
  • Urea Cycle Disorders, Inborn / therapy


  • Ammonia
  • Urea