5-oxoprolinemia causing elevated anion gap metabolic acidosis in the setting of acetaminophen use

J Emerg Med. 2012 Jul;43(1):54-7. doi: 10.1016/j.jemermed.2011.06.017. Epub 2011 Oct 5.


Background: Anion gap metabolic acidosis is typically encountered in the emergency department (ED) setting as the result of shock, other endogenous metabolic derangements, or from exogenous toxicants. The differential diagnosis for toxicant-related acidosis (exemplified by common mnemonics) emphasizes acute overdose.

Case report: The case we present manifested an anion gap (AG) metabolic acidosis due to a chronic intoxication: acetaminophen (APAP) overuse over a period of weeks. Lactic acidemia did not account for the AG. In this case, chronic APAP overuse, combined with decreased caloric intake and weight loss, was associated with excess 5-oxoproline (pyroglutamic acid), an organic acid accounting for the AG metabolic acidosis. Overproduction of 5-oxoproline is attributed to depleted glutathione stores, leading to perturbation in the γ-glutamyl cycle. The patient was treated with supportive care and with N-acetylcysteine (NAC). By repleting glutathione, NAC may facilitate the resolution of excess 5-oxoproline.

Conclusions: The ED differential diagnosis of AG metabolic acidosis in chronic APAP overuse, especially with concomitant nutritional compromise, should include 5-oxoprolinemia.

Publication types

  • Case Reports

MeSH terms

  • Acetaminophen / poisoning*
  • Acetylcysteine / therapeutic use
  • Acid-Base Equilibrium
  • Acidosis / etiology*
  • Adult
  • Amino Acid Metabolism, Inborn Errors / chemically induced*
  • Amino Acid Metabolism, Inborn Errors / complications
  • Amino Acid Metabolism, Inborn Errors / drug therapy
  • Analgesics, Non-Narcotic / poisoning*
  • Female
  • Free Radical Scavengers / therapeutic use
  • Glutathione Synthase / deficiency
  • Humans


  • Analgesics, Non-Narcotic
  • Free Radical Scavengers
  • Acetaminophen
  • Glutathione Synthase
  • Acetylcysteine

Supplementary concepts

  • Glutathione synthetase deficiency