Severe Anion Gap Metabolic Acidosis Resulting from Combined Chronic Acetaminophen Toxicity and Starvation Ketosis: A Case Report

Patient: Male, 68-year-old Final Diagnosis: 5-oxoproline toxicity • anion gap metabolic acidosis • starvation ketoacidosis Symptoms: Confusion • weakness Medication: — Clinical Procedure: — Specialty: General and Internal Medicine • Nephrology OBJECTIVE: Rare coexistence of disease or pathology BACKGROUND: Chronic acetaminophen toxicity has been known to cause anion gap metabolic acidosis (AGMA) due to accumulation of 5-oxoproline metabolites. This diagnosis requires a high index of suspicion because acetaminophen use is very common among patients, it is often difficult to gauge the extent of use, and patients often have multiple comorbid conditions complicating diagnoses. CASE REPORT: A 68-year-old man with multiple medical comorbidities presented to the Emergency Department with recurrent generalized weakness. On all occasions, the patient denied focal weakness or infectious symptoms. He also denied ingestions other than prescribed medications, including acetaminophen 325 mg as needed, which he described taking “a couple times” a day. His vital signs were normal other than tachypnea to 28 breaths/min. The physical examination was notable for Kussmaul breathing pattern and slight confusion. The patient’s prior 3 presentations were notable for profound AGMA, hypernatremia, acute kidney injury, and ketosis. As the patient’s blood urea nitrogen, blood sugar, liver tests, lactic acid, and serum osmolality were normal, the patient was diagnosed with “starvation ketosis” and received supportive care each time with fluids and sodium bicarbonate. Further investigation at his final admission revealed an elevated 5-oxoproline level and a delayed diagnosis of chronic acetaminophen toxicity. CONCLUSIONS: This report emphasizes the need for a high index of suspicion related to chronic acetaminophen toxicity and other ingestions contributing to a metabolic acidosis in at-risk populations, even when routine history is unrevealing. Furthermore, severe acidosis should prompt more extensive investigation when out of proportion to obvious routine etiologies.