Adult-onset citrullinaemia type II (CTLN2) is a rare disease in Chinese patients. As a subtype of citrin deficiency (CD), it is an autosomal recessive disease related to the SLC25A13 mutation on chromosome 7q21.3. In this study, we report a case of CTLN2 presenting with paroxysmal altered consciousness and refractory hyperammonaemia. The diagnosis was finally confirmed by gene analysis. The patient recovered after liver transplantation. It can be learned from this case that CD should be considered in patients with refractory hyperammonaemia and paroxysmal mental disorder without a history of liver disease.