First two cases of adult-onset type II citrullinemia successfully treated by deceased-donor liver transplantation in Japan

Clinical landscape of citrin deficiency: A global perspective on a multifaceted condition

Citrin deficiency is an autosomal recessive disorder caused by a defect of citrin resulting from mutations in SLC25A13. The clinical manifestation is very variable and comprises three types: neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD: OMIM 605814), post-NICCD including failure to thrive and dyslipidemia caused by citrin deficiency, and adult-onset type II citrullinemia (CTLN2: OMIM 603471). Frequently, NICCD can run with a mild clinical course and manifestations may resolve in the post-NICCD. However, a subset of patients may develop CTLN2 when they become more than 18 years old, and this condition is potentially life-threatening. Since a combination of diet with low-carbohydrate and high-fat content supplemented with medium-chain triglycerides is expected to ameliorate most manifestations and to prevent the progression to CTLN2, early detection and intervention are important and may improve long-term outcome in patients. Moreover, infusion of high sugar solution and/or glycerol may be life-threatening in patients with citrin deficiency, particularly CTLN2. The disease is highly prevalent in East Asian countries but is more and more recognized as a global entity. Since newborn screening for citrin deficiency has only been introduced in a few countries, the diagnosis still mainly relies on clinical suspicion followed by genetic testing or selective metabolic screening. This paper aims at describing (1) the different stages of the disease focusing on clinical aspects; (2) the current published clinical situation in East Asia, Europe, and North America; (3) current efforts in increasing awareness by establishing management guidelines and patient registries, hereby illustrating the ongoing development of a global network for this rare disease.

Citrin Deficiency: Clinical and Nutritional Features

SLC25A13 gene mutations are responsible for diseases related to citrin deficiency (CD), such as neonatal intrahepatic cholestasis caused by citrin deficiency and adult-onset type II citrullinemia (CTLN2). From childhood to adulthood, CD patients are apparently healthy due to metabolic compensation with peculiar dietary habits-disliking high-carbohydrate foods and liking fat and protein-rich foods. Carbohydrate overload and alcohol consumption may trigger the sudden onset of CTLN2, inducing hyperammonemia and consciousness disturbance. Well-compensated asymptomatic CD patients are sometimes diagnosed as having non-obese (lean) non-alcoholic fatty liver disease and steatohepatitis, which have the risk of developing into liver cirrhosis and hepatocellular carcinoma. CD-induced fatty liver demonstrates significant suppression of peroxisome proliferator-activated receptor α and its downstream enzymes/proteins involved in fatty acid transport and oxidation and triglyceride secretion as a very low-density lipoprotein. Nutritional therapy is an essential and important treatment of CD, and medium-chain triglycerides oil and sodium pyruvate are useful for preventing hyperammonemia. We need to avoid the use of glycerol for treating brain edema by hyperammonemia. This review summarizes the clinical and nutritional features of CD-associated fatty liver disease and promising nutritional interventions.

Three cases of adult-onset type II citrullinemia treated with different therapies: Efficacy of sodium pyruvate and low-carbohydrate diet

We report three cases of adult-onset type II citrullinemia (CTLN2) treated with different therapies including one case successfully treated with p.o. administration of sodium pyruvate and low-carbohydrate diet. Although recent advances in liver transplantation have enabled successful treatment of patients with CTLN2, several issues concerning liver transplantation remain. Further, there is still an urgent need for therapies that do not rely on liver transplantation. The first case was a 41-year-old man who developed impaired consciousness in 1992. The patient was treated with conventional therapy for hepatic encephalopathy and died of severe brain edema. The second case was a 31-year-old man who suddenly presented a syncope-like attack with hyperammonemia. He was treated with carbohydrate-restricted diet but the encephalopathy could not be controlled, and he received emergency living donor liver transplantation. The third patient was a 67-year-old man who developed abnormal behavior with hyperammonemia. He has remained well with oral sodium pyruvate and a low-carbohydrate diet without receiving liver transplantation.