Metabolic acidosis in late pregnancy due to 5-oxoproline (pyroglutamic acid)—A case report

Introduction: Accumulation of 5-oxoproline (pyroglutamic acid) is a rare cause of severe, high anion gap metabolic acidosis in adults. Case: A 21 year old lady presented at 39 weeks gestation in her first pregnancy with 2 weeks history of shortness of breath. She suffered from ear ache and had been taking Paracetamol on regular basis for a year. She was admitted to having regular alcohol intake until the pregnancy when she stopped. She was not in acute distress and all her observations were stable. The laboratory analysis of renal function was normal. Arterial blood gas showed metabolic acidosis. The anion gap 34 mEq/l which was consistent with metabolic acidosis. Plasma aminoacid screen revealed no abnormality. Chest X-rays showed patchy consolidation keeping with a chest infection. Emergency caesarean section was carried out for fetal distress in first stage of labour. Urine and serum samples were taken which showed an increase in the serum level five Oxoproline to creatinine ratio indicating pyroglutamic metabolic acidosis. Polyglutamate was found in the urine She was admitted to intensive care unit; cardiovascular stable, had no signs of sepsis. She underwent ventilation and haemofiltration. On second day of admission metabolic acidosis was corrected. During the 48 hours treatment with supportive therapy produced general overall improvement. Discussion: Metabolic acidosis that caused by 5-oxoproline results from disruption of the gamma glutamyl cycle. Glutamile synthetase (GS) deficiency is an autosomol recessive disorder. With GS deficiency, reduced glutathione levels increase gamma glutamile synthetase activity, and the resulting gamma—glutamile cystine levels are particularly converted to 5-oxoproline. Intoxication of organic acids is a differential diagnosis of high anion gap metabolic acidosis with no renal impairment, there was no evidence of ethanol, methanol or ethylene glycol ingestion. Suspicion for 5oxoproline-associated high anion gap metabolic acidosis should be entertained when the cause of high anion gap metabolic acidosis remains poorly defined, the anion gap cannot be explained reasonably by measured organic acids, and there is concomitant acetaminophen use. Conclusion: Clinicians need to be aware of this unusual cause of anion gap acidosis because it may be more common than expected, early discontinuation of the offending agent is therapeutic, and administration of N-acetylcysteine could be beneficial.