Pyroglutamate acidosis 2023. A review of 100 cases

This review concerns the rare, acquired, usually iatrogenic, high-anion-gap metabolic acidosis, pyroglutamic acidosis. Pyroglutamate is a derivative of the amino acid glutamate, and is an intermediate in the 'glutathione cycle', by which glutathione is continuously synthesized and broken down. The vast majority of pyroglutamic acidosis cases occur in patients on regular, therapeutic doses of paracetamol. In about a third of cases, flucloxacillin is co-prescribed. In addition, the patients are almost always seriously unwell in other ways, typically with under-nourishment of some form. Paracetamol, with underlying disorders, conspires to divert the glutathione cycle, leading to the overproduction of pyroglutamate. Hypokalaemia is seen in about a third of cases. Once the diagnosis is suspected, it is simple to stop the paracetamol and change the antibiotic (if flucloxacillin is present), pending biochemistry. N-acetyl-cysteine can be given, but while the biochemical justification is compelling, the clinical evidence base is anecdotal.

High anion gap metabolic acidosis induced by cumulation of ketones, L- and D-lactate, 5-oxoproline and acute renal failure

INTRODUCTION

Frequent causes of high anion gap metabolic acidosis (HAGMA) are lactic acidosis, ketoacidosis and impaired renal function. In this case report, a HAGMA caused by ketones, L- and D-lactate, acute renal failure as well as 5-oxoproline is discussed.

CASE PRESENTATION

A 69-year-old woman was admitted to the emergency department with lowered consciousness, hyperventilation, diarrhoea and vomiting. The patient had suffered uncontrolled type 2 diabetes mellitus, underwent gastric bypass surgery in the past and was chronically treated with high doses of paracetamol and fosfomycin. Urosepsis was diagnosed, whilst laboratory analysis of serum bicarbonate concentration and calculation of the anion gap indicated a  HAGMA. L-lactate, D-lactate, β-hydroxybutyric acid, acetone and 5-oxoproline serum levels were markedly elevated and renal function was impaired.

DISCUSSION

We concluded that this case of HAGMA was induced by a variety of underlying conditions: sepsis, hyperglycaemia, prior gastric bypass surgery, decreased renal perfusion and paracetamol intake. Risk factors for 5-oxoproline intoxication present in this case are female gender, sepsis, impaired renal function and uncontrolled type 2 diabetes mellitus. Furthermore, chronic antibiotic treatment with fosfomycin might have played a role in the increased production of 5-oxoproline.

CONCLUSION

Paracetamol-induced 5-oxoproline intoxication should be considered as a cause of HAGMA in patients with female gender, sepsis, impaired renal function or uncontrolled type 2 diabetes mellitus, even when other more obvious causes of HAGMA such as lactate, ketones or renal failure can be identified.