Unmasked adult-onset urea cycle disorders in the critical care setting

Crit Care Clin. 2005 Oct;21(4 Suppl):S1-8. doi: 10.1016/j.ccc.2005.05.002.


Most often, urea cycle disorders have been described as acute onset hyperammonemia in the newborn period; however, there is a growing awareness that urea cycle disorders can present at almost any age, frequently in the critical care setting. This article presents three cases of adult-onset hyperammonemia caused by inherited defects in nitrogen processing in the urea cycle, and reviews the diagnosis, management, and pathophysiology of adult-onset urea cycle disorders. Individuals who have milder molecular urea cycle defects can lead a relatively normal life until a severe environmental stress triggers a hyperammonemic crisis. Comorbid conditions such as physical trauma often delay the diagnosis of the urea cycle defect. Prompt recognition and treatment are essential in determining the outcome of these patients.

Publication types

  • Case Reports
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Adult
  • Age of Onset
  • Brain Diseases, Metabolic, Inborn* / diagnosis
  • Brain Diseases, Metabolic, Inborn* / etiology
  • Brain Diseases, Metabolic, Inborn* / therapy
  • Carbamoyl-Phosphate Synthase I Deficiency Disease / diagnosis
  • Carbamoyl-Phosphate Synthase I Deficiency Disease / etiology
  • Carbamoyl-Phosphate Synthase I Deficiency Disease / therapy
  • Critical Illness*
  • Emergencies
  • Female
  • Humans
  • Hyperammonemia* / diagnosis
  • Hyperammonemia* / etiology
  • Hyperammonemia* / therapy
  • Male
  • Middle Aged
  • Ornithine Carbamoyltransferase Deficiency Disease / diagnosis
  • Ornithine Carbamoyltransferase Deficiency Disease / etiology
  • Ornithine Carbamoyltransferase Deficiency Disease / therapy
  • Precipitating Factors
  • Urea / metabolism*


  • Urea