5-Oxoprolinemia in a Patient With Severe Hypothyroidism and Chronic Acetaminophen Use

5-oxoprolinemia is caused by a defect in the gamma-glutamyl pathway which can present with severe anion gap metabolic acidosis not caused by ketoacidosis, lactic acidosis, methanol/ethylene glycol ingestion, renal failure, ethanol, iron/isoniazid or salicylate ingestion. This case will describe a 59-year-old female presenting with elevated anion gap metabolic acidosis with no discernible classical cause, chronic acetaminophen use, malnourishment, and severe hypothyroidism with 5-oxoprolinemia after extensive investigation of other causes. Treatment involved correcting the acidosis with bicarbonate, IV fluid administration, oral levothyroxine and avoiding further acetaminophen use. The patient's acidosis resolved soon after and she was counseled on the avoidance of acetaminophen in the future. This case highlights the importance of pharmacologic vigilance with everyday over-the-counter medicines such as acetaminophen and metabolic states such as hypothyroidism which can lead to tumultuous cases of metabolic acidosis. This is the first case in which we know that 5-oxoprolinemia has presented with concomitant severe hypothyroidism. Due to this patient's course, it may have been the preceding factor for the development of her oxoprolinemia alongside her acetaminophen consumption.