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Abstract: SA-PO494

L-Arginine-Induced Non-Anion Gap Metabolic Acidosis in a Patient With MELAS Syndrome

Session Information

Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders

  • 1002 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Clinical


  • Rechlin, Daniel, University of Rochester Medical Center, Rochester, New York, United States
  • Moore, Catherine A., University of Rochester Medical Center, Rochester, New York, United States

MELAS syndrome (Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) is a rare disorder of mitochondrial DNA manifesting across multiple body systems, including with episodic lactic acidosis. Primary treatment of flares is with L-arginine. This medication has been shown to inhibit proximal renal tubule bicarbonate reabsorption, and we present a complicated case of this known but rare side effect.

Case Description

Our patient was a 40 year old male with a history of MELAS syndrome with subsequent seizures, hearing and visual loss, and previous stoke-like episodes; hypertension; and type 2 diabetes mellitus treated with Empagliflozin. He presented to the hospital with 2-3 days of abdominal pain and malaise, with acute onset encephalopathy. Initial workup revealed an anion gap metabolic acidosis (AGMA), with evidence of lactic acidosis and DKA, and concurrent respiratory acidosis. He initially responded to IV fluids, insulin infusion, and mechanical ventillation. On hospital day 2 he was started on IV L-Arginine for suspected MELAS flare. The next day there was recurrence of AGMA, with additional non-anion gap metabolic acidosis (NAGMA). AGMA, attributed to recurrence of euglycemic DKA vs. starvation ketosis, resolved with additional IV fluids and insulin infusion. Given the timeline, and urine labs consistent with type II renal tubular acidosis, his Arginine infusions were felt to be the most likely culprit for his NAGMA. He was treated with temporary bicarbonate supplementation, and with completion of his course of L-Arginine his acidosis resolved.


This is a case of L-arginine induced non anion gap metabolic acidosis in a patient with MELAS syndrome. Although there have been occasional reports of this phenomenon, there is very little literature on this topic. This patient's case was also complicated by multiple other sources of metabolic, and respiratory, acidosis. Patients with MELAS syndrome are prone to complicated acid-base disturbances by nature of their disease. NAGMA from L-arginine is a medication side effect peculiar to this combination of therapy and disease process. Because of the multiple potential pitfalls in diagnosis illustrated by this case, it is important to bear this in mind when caring for patients with this rare disease.