Abstract

Adult-onset citrullinemia (CTLN2) is a rare hereditary metabolic disorder characterized by highly increased concentration of citrulline and ammonia in the plasma, which is ascribed to a deficiency of argininosuccinate synthetase (ASS), one of the urea cycle enzymes mainly located in the liver. Neurological manifestation in CTLN2 patients closely resemble those of hepatic encephalopathy and in the past, most patients usually followed rapidly deteriorating clinical courses and died of severe brain edema within a few years after onset. However, in 1995 the first CTLN2 patient who was successfully treated by living-related liver transplantation was reported and since then more than 30 patients had underwent this operation in our country, showing good outcomes. No primary defect had not been found within ASS gene locus, but the causative gene of this disorder is now identified as the "citrin gene", which might act as a aspartate/glutamate transporter in mitochondria. Different phenotypes are seen in the individuals with a citrin deficiency: neonatal intrahepatic cholestasis, juvenile-onset chronic pancreatitis and hepatocellular carcinoma without cirrhosis can precede the appearance of CTLN2. The precise pathogenesis of this disease that includes the relationship between the mutations of citrin gene and a deficiency of hepatic ASS activity remains unclear.