311: SEVERE HYPERAMMONEMIA CAUSED BY CARNITINE DEFICIENCY DURING ADULTHOOD

Abstract

Introduction: Carnitine is a necessary co-factor in the oxidation of fatty acids as part of the urea cycle; deficiency of which may lead to heart or liver failure. Primary carnitine deficiency due to transporter defects or mutations is seen in infants. Secondary carnitine deficiency is the result of whole-body carnitine deficiency. Here, we discuss a case of secondary deficiency due to vegetarianism, leading to severe hyperammonemia. Description: A 23-year-old woman was admitted with one day of vomiting and diarrhea. On arrival, she was confused but alert, though rapidly decompensated and developed obtundation, clonus, rigidity, posturing, and non-reactive mydriatic pupils, requiring emergent intubation. Work-up was significant for elevated ammonia to 581 umol/L with CT head showing severe brain edema prompting placement of external ventricular drain for intracranial hypertension and frequent hypertonic saline administration. Given significant hyperammonemia with otherwise negative work-up, the patient’s presentation was concerning for a urea cycle defect. The patient was dialyzed and started on arginine, sodium benzoate/phenylacetate, citrulline, and buphenyl. Further history revealed a diet devoid of meat. Plasma amino acid analysis revealed decreased total carnitine 3 umol/L (27-73) and free carnitine 2 umol/L (20-55). There were no mutations in the carnitine transport gene or deficient enzymatic activity for the urea cycle. After one week, she was awake, alert, and was extubated shortly thereafter. Once tolerating oral intake, her diet of was supplemented with oral carnitine. She was able to make a full recovery and return home without deficits from baseline prior to admission. Discussion: Common causes of hyperammonemia are hepatic failure, genetic urea cycle defects, and organic academies, which were ruled out in this case. Carnitine is an important co-factor in the metabolism of long-chain fatty acids and its disruption impairs ammonia excretion through inhibition of the urea cycle. Secondary carnitine deficiency is seen in severe malnutrition, and causes hyperammonemia and encephalopathy. This case is particularly important to note, as fatty acid oxidation disorders based on pure dietary deficiency that presents during adulthood are uncommon and not frequently considered in the differentials.