We report on an adult patient with citrin deficiency in Hong Kong, in whom a novel mutation was identified. The patient presented with recurrent hyperammonaemic encephalopathy due to impairment of the liver urea cycle enzyme argininosuccinate synthetase. This autosomal recessive condition is also characterised by interesting food preferences, notably aversion to carbohydrates and craving for protein-rich and/or lipid-rich foods, as well as neuropsychiatric symptoms. Plasma amino acid analysis is very useful in revealing urea cycle disorders, and mutational analysis of the SLC25A13 gene can confirm the diagnosis.