Case We report a 57-year old woman, presented with a prolonged history of abnormal behavior, aggression, paranoia, and hyperactivity. There was evidence of non-convulsive status epilepticus on electroencephalogram, which subsequently improved with Levetiracetam, Phenytoin and Lamotrigine treatment. Liver function tests were deranged and serum ammonia was persistently raised up to 111 µmol/L with a fatty liver deposition on ultrasound. No responsible medication or primary liver or porto-shunt system was identified. Clinical features and serum ammonia improved with a high protein and low carbohydrate diet. Plasma amino acids showed no significant abnormalities except for an increased citrulline of 54 µmol/L. Genetic testing for SLC25A13 gene mutation was negative. Whole genome sequencing is being carried out. Treatment with sodium benzoate, dietary restriction of proteins and anti-epileptic medications resolved non-convuslive status epilepticus on EEG, and moderately improved hyperammonaemia.

Conclusion Correct diagnosis and specific dietary treatment is crucial to ensure a good prognosis in patients with hypercitrullinaemia. This should be considered as a differential diagnosis in patients with persistent non-hepatic hyperammonaemia. There might be as yet unrecognised gene defects responsible for hypercitrullinaemia.