Update on the diagnosis and management of neonatal intrahepatic cholestasis caused by citrin deficiency: Expert review on behalf of the Asian Pan-Pacific Society for Pediatric Gastroenterology, Hepatology, and Nutrition.

Citrin deficiency is an autosomal recessive metabolic liver disease caused by mutations in the SLC25A13 gene. The disease typically presents with cholestasis, elevated liver enzymes, hyperammonemia, hypercitrullinemia, and fatty liver in young infants, resulting in a phenotype known as "neonatal intrahepatic cholestasis caused by citrin deficiency" (NICCD). The diagnosis relies on clinical manifestation, biochemical evidence of hypercitrullinemia, and identifying mutations in the SLC25A13 gene. Several common mutations have been found in patients of East Asian background. The mainstay treatment is nutritional therapy in early infancy utilizing a lactose-free and medium-chain triglyceride formula. This approach leads to the majority of patients recovering liver function by 1 year of age. Some patients may remain asymptomatic or undiagnosed, but a small proportion of cases can progress to cirrhosis and liver failure, necessitating liver transplantation. Recently, advancements in newborn screening methods have improved the age of diagnosis. Early diagnosis and timely management improve patient outcomes. Further studies are needed to elucidate the long-term follow-up of NICCD patients into adolescence and adulthood.

[Analysis of clinical and genetic variation in neonatal intrahepatic cholestasis caused by citrin deficiency].

Objective: To investigate the clinical phenotype and gene variation conditions in neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD), so as to provide a basis for genetic counseling and clinical diagnosis and treatment of the family. Methods: 11 cases of neonatal intrahepatic cholestasis who visited the Children's Hospital Affiliated to Zhengzhou University between February 2019 and March 2021 were selected as the study subjects. High-throughput sequencing technology was used to detect the gene variation condition in 11 neonatal patients and 100 normal control neonates. The suspicious loci and family members were verified by Sanger sequencing and QPCR technology. Results: All 11 children with NICCD had different degrees of jaundice and liver damage symptoms, combined with coagulation dysfunction and anemia (n = 7), cardiac malformation (n = 2), elevated myocardial enzymes (n = 4), hyperlipidemia (n = 1), hyperkalemia (n = 1), persistent diarrhea (n = 3), developmental delay (n = 1). A total of 10 different types of SLC25A13 gene mutations were detected in 11 cases, including three frameshift mutations, two splicing changes, two missense mutations, one intron insertion, one nonsense mutation, and one heterozygous deletion. After reviewing literature and databases, c.1878delG(p.I627Sfs*73) and exon11 deletion were novel mutations that had not been reported at home or abroad. Conclusion: The clinical features of NICCD are non-specific, and genetic testing aids in the early and accurate diagnosis of the disease, providing an important basis for clinical treatment and genetic counseling for family members. In addition, the detection of novel mutation sites has enriched the SLC25A13 gene variation spectrum.

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.

The prognosis of citrin deficiency differs between early-identified newborn and later-onset symptomatic infants.

BACKGROUND: The prognosis for patients with citrin deficiency is not always benign. This study examined the differences between patients identified early by newborn screening and patients identified later with cholestasis/hepatitis. MATERIALS AND METHODS: This retrospective study included 42 patients with genetically confirmed SLC25A13 mutations who were born between May 1996 and August 2019. Fifteen patients were identified during newborn screening (NBS group) and 27 patients were identified through the onset of cholestasis/hepatitis in infancy (clinical group). RESULTS: Overall, 90% of the patients presented with cholestasis, among whom 86% (31/36) recovered at a median age of 174 days. Compared with patients in the clinical group, patients in the NBS group were significantly younger at diagnosis and at cholestasis-free achievement; they also had significantly lower levels of peak direct bilirubin and liver enzymes. At the median follow-up age of 11.8 years, 21% of the patients had dyslipidemia, whereas 36% of the patients had failure to thrive. The overall mortality rate was 2.4%. Variant c.851_854del was the most frequent, constituting 44% of the mutant alleles. CONCLUSION: Patients identified early by NBS had a better prognosis, demonstrating the importance of a timely diagnosis of NICCD and the need for careful follow-up. IMPACT: Some cases of neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) are not benign. Compared with patients identified later based on the presence of cholestasis/hepatitis, patients identified early by newborn screening have less severe cholestasis and are cholestasis-free at a significantly younger age. A timely diagnosis is needed, along with follow-up examinations that assess metabolic profile and body weight, to improve the long-term prognosis of NICCD patients.

Anesthetic Management of a Patient With Citrullinemia Type I During Dental Treatment.

We report a case involving intravenous sedation for third molar extractions in a 32-year-old man with citrullinemia type I (CTLN1), a genetic disorder that affects the urea cycle. The patient was diagnosed with CTLN1 after he exhibited seizures soon after birth and was intellectually disabled because of persistent hyperammonemia, although his recent serum ammonia levels were fairly well controlled. We planned to minimize his preoperative fasting, continue his routine oral medications, and monitor his serum ammonia levels at least twice. Sedation with midazolam and a propofol infusion was planned to suppress his gag reflex and reduce protein hypercatabolism due to stress. Epinephrine-containing local anesthetics, which enhance protein catabolism, were avoided, replaced by plain lidocaine for blocks and prilocaine with felypressin for infiltration anesthesia. No significant elevation in ammonia levels was observed. In patients with CTLN1, sedation can be useful for preventing hyperammonemia. Patients who develop symptomatic hyperammonemia may require urgent/emergent treatment involving other medical specialists. Therefore, preoperative endocrinology consultation, perioperative monitoring of serum ammonia levels, and preemptively coordinating for appropriate care in the event hyperammonemia occurs should all be considered.

Hypoglycemic attacks and growth failure are the most common manifestations of citrin deficiency after 1 year of age.

Citrin deficiency develops in different symptomatic periods from the neonatal period to adulthood. Some infantile patients are diagnosed by newborn mass screening or symptoms of neonatal intrahepatic cholestasis caused by citrin deficiency, some patients in childhood may develop hepatopathy or dyslipidemia as failure to thrive and dyslipidemia caused by citrin deficiency, and some adults are diagnosed after developing adult-onset type 2 citrullinemia (CTLN2) with hyperammonemia or encephalopathy. A diagnosis is needed before the development of severe phenotypic CTLN2 but is often difficult to obtain because newborn mass screening cannot detect all patients with citrin deficiency, and undiagnosed patients often appear healthy in childhood. There are only a few reports that have described patients in childhood. To explore the clinical features of undiagnosed patients with citrin deficiency in childhood, we studied 20 patients who were diagnosed after the first year of life. Of these patients, 45% experienced hypoglycemic attacks in childhood. The acetoacetic acid level during hypoglycemic attacks was lower than expected. Growth failure at diagnosis (45%) was also noted. From the patients' history, fat- and protein-rich food preferences (80%), a low birth weight (70%), and prolonged jaundice or infantile hepatopathy (40%) were identified. To diagnose citrin deficiency in childhood, we should ask about food preferences and a history of infantile hepatopathy for all children with severe hypoglycemia or growth failure and consider the genetic test for citrin deficiency if the patient has characteristic food preferences or a history of infantile hepatopathy.

Combined primary carnitine deficiency with neonatal intrahepatic cholestasis caused by citrin deficiency in a Chinese newborn.

BACKGROUND: Primary carnitine deficiency (PCD) is an autosomal recessive disorder affecting the carnitine cycle and resulting in defective fatty acid oxidation. Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) is an autosomal recessive disorder and one of the main causes of inherited neonatal cholestasis. Both PCD and NICCD are included in the current expanded newborn screening (NBS) targets. CASE PRESENTATION: Targeted exome sequencing was performed on a Chinese proband, and Sanger sequencing was utilised to validate the detected mutations. The patient who was initially suspected to have PCD based on the NBS results presented with neonatal intrahepatic cholestasis and ventricular septal defect. Further investigations not only confirmed PCD but also revealed the presence of NICCD. Four distinct mutations were detected, including c.51C > G (p.F17L) and c.760C > T (p.R254X) in SLC22A5 as well as c.615 + 5G > A and IVS16ins3kb in SLC25A13. CONCLUSIONS: This is the first reported case of PCD and NICCD occurring in the same patient. The dual disorders in a newborn broaden our understanding of inherited metabolic diseases. Thus, this study highlighted the importance of further genetic testing in patients presenting with unusual metabolic screening findings.

Neonatal cholestasis due to citrin deficiency: diagnostic pitfalls.

Citrin deficiency can manifest in newborns or infants as neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD). The paper presents a case of Polish NICCD patient presenting with low birth weight, failure to thrive, prolonged cholestatic jaundice with coagulopathy and hypoalbuminemia with normal results of MS/MS newborn screening but with high blood citrulline level observed at 3 months of age. Unreported findings included N-hypoglycosylation and increased serum very-long-chain fatty acids (VLCFA), probably secondary to liver impairment. Final diagnosis was established based on whole-exome sequencing (WES) analysis.

Chronic pancreatitis and pancreatic pseudocyst with adult-onset type II citrullinemia.

Citrin deficiency, which is caused by a mutation of SCL25A13, can manifest in older children as failure to thrive and dyslipidemia caused by citrin deficiency (FTTDCD) and in adults as recurrent hyperammonemia with neuropsychiatric symptoms in adult-onset type II citrullinemia (CTLN2). FTTDCD and CTLN2 are known to complicate hypertriglyceridemia and chronic pancreatitis. Here we report, for the first time, the case of a patient with chronic pancreatitis and pancreatic pseudocyst with CTLN2 who was treated using endoscopic ultrasound-guided cyst drainage (EUS-CD). A 33-year-old woman with down syndrome presented to our hospital with complaints of fever, abdominal distention, and biliary vomiting for the previous 2 weeks. Owing to her difficulties in communication, although she had been taking a nutritionally balanced diet regardless of her preference, chronic pancreatitis and pancreatic stones had already been observed at the time of CTLN2 diagnosis at the age of 30 years. Three years later, a merged pancreatic pseudocyst was detected, and EUS-CD was successfully performed. A high-fat diet therapy for FTTDCD and CTLN2 may have caused the development of the pancreatic pseudocyst combined with chronic pancreatitis in this case. Pancreatic pseudocysts associated with FTTDCD or CTLN2 can be treated in a similar manner to those resulting from other causes.

Combining newborn metabolic and genetic screening for neonatal intrahepatic cholestasis caused by citrin deficiency.

To evaluate the feasibility of incorporating genetic screening for neonatal intrahepatic cholestasis, caused by citrin deficiency (NICCD), into the current newborn screening (NBS) program. We designed a high-throughput iPLEX genotyping assay to detect 28 SLC25A13 mutations in the Chinese population. From March 2018 to June 2018, 237 630 newborns were screened by tandem mass spectrometry at six hospitals. Newborns with citrulline levels between 1/2 cutoff and cutoff values of the upper limit were recruited for genetic screening using the newly developed assay. The sensitivity and specificity of the iPLEX genotyping assay both reached 100% in clinical practice. Overall, 29 364 (12.4%) newborns received further genetic screening. Five patients with conclusive genotypes were successfully identified. The most common SLC25A13 mutation was c.851_854del, with an allele frequency of 60%. In total, 658 individuals with one mutant allele were identified as carriers. Eighteen different mutations were observed, yielding a carrier rate of 1/45. Notably, Quanzhou in southern China had a carrier rate of up to 1/28, whereas Jining in northern China had a carrier rate higher than that of other southern and border cities. The high throughput iPLEX genotyping assay is an effective and reliable approach for NICCD genotyping. The combined genetic screening could identify an additional subgroup of patients with NICCD, undetectable by conventional NBS. Therefore, this study demonstrates the viability of incorporating genetic screening for NICCD into the current NBS program.

Growth impairment in individuals with citrin deficiency.

Citrin deficiency causes neonatal intrahepatic cholestasis (NICCD), failure to thrive and dyslipidemia (FTTDCD), and adult-onset type II citrullinemia (CTLN2). Owing to a defect in the NADH-shuttle, citrin deficiency impairs hepatic glycolysis and de novo lipogenesis leading to hepatic energy deficit. To investigate the physiological role of citrin, we studied the growth of 111 NICCD-affected subjects (51 males and 60 females) and 12 NICCD-unaffected subjects (five males and seven females), including the body weight, height, and genotype. We constructed growth charts using the lambda-mu-sigma (LMS) method. The NICCD-affected subjects showed statistically significant growth impairment, including low birth weight and length, low body weight until 6 to 9 months of age, low height until 11 to 13 years of age, and low body weight in 7 to 12-year-old males and 8-year-old females. NICCD-unaffected subjects showed similar growth impairment, including low birth weight and height, and growth impairment during adolescence. In the third trimester, de novo lipogenesis is required for deposition of body fat and myelination of the developing central nervous system, and its impairment likely causes low birth weight and length. The growth rate is the highest during the first 6 months of life and slows down after 6 months of age, which is probably associated with the onset and recovery of NICCD. Adolescence is the second catch-up growth period, and the proportion and distribution of body fat change depending on age and sex. Characteristic growth impairment in citrin deficiency suggests a significant role of citrin in the catch-up growth via lipogenesis.

A 6-Year-Old Child With Citrin Deficiency and Advanced Hepatocellular Carcinoma.

We report the case of a 6-year-old boy with citrin deficiency and advanced hepatocellular carcinoma diagnosed by using imaging. He exhibited intrahepatic cholestasis 2 days after his birth and was misdiagnosed with inspissated bile syndrome at that time. The symptoms of jaundice spontaneously resolved when he was 5 months old. However, his transaminase levels remained elevated for ∼6 years, for which he received no treatment. He preferred a high-protein, high-fat, low-carbohydrate diet, which has been observed in many patients with citrin deficiency, but no clinical features of adult-onset type II citrullinemia were observed. At the age of 6 years, he was admitted to our hospital with a nonviral infection and high α-fetoprotein level; results from an abdominal MRI and computed tomography revealed multiple tumors in the liver. Because of his history of intrahepatic cholestasis in the neonatal period, he was suspected to have citrin deficiency. A genetic analysis of solute carrier family 25, member 13 revealed the presence of a homozygous 851del4 mutation, and a diagnosis of citrin deficiency was made. The patient did not qualify for liver transplantation and died 2 months later, after discharge from our hospital. Thus, this case reveals that not all patients with neonatal intrahepatic cholestasis spontaneously and totally improve, and this case is used to emphasize that patients with neonatal intrahepatic cholestasis should be managed carefully, especially in the stage of failure to thrive and dyslipidemia caused by citrin deficiency, which may lead to advanced hepatocellular carcinoma.

Neonatal Lupus Erythematosus in a newborn with Citrullinemia.

A 24-day-old female newborn presented with multiple annular erythematous plaques with a targetoid shape, on the forehead, neck and upper trunk, that had begun ten days earlier. She had been diagnosed with citrullinemia type 1 in the first week of life and arginine supplementation was initiated. Her personal and family history was otherwise unremarkable. Laboratory tests showed high levels of anti-La/SSB and anti-Ro/SSA in both mother and baby. The patient was diagnosed with Neonatal lupus erythematosus on the basis of the clinical, histopathological and laboratorial findings. Neonatal lupus is a rare immune-mediated disease that results from transplacental transfer of maternal IgG antinuclear antibodies. The disease can affect different organs, mainly the skin and heart. Although the skin lesions are usually characteristic, they pose a diagnostic challenge in the absence of maternal history.

Cholesterol Metabolism Is Enhanced in the Liver and Brain of Children With Citrin Deficiency.

Context: Citrin-deficient infants present neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD), which resolves at 12 months. Thereafter, they have normal liver function associated with hypercholesterolemia, and a preference for lipid-rich carbohydrate-restricted diets. However, some develop adult-onset type II citrullinemia, which is associated with metabolic abnormalities. Objectives: To identify the causes of hypercholesterolemia in citrin-deficient children post-NICCD. Design and Setting: We determined the concentrations of sterol markers of cholesterol synthesis, absorption, and catabolism by liquid chromatography-electrospray ionization-tandem mass spectrometry and evaluated serum lipoprotein profiles. Subjects: Twenty citrin-deficient children aged 5 to 13 years and 37 age-matched healthy children. Intervention: None. Main Outcome Measures: Relationship between serum lipoproteins and sterol markers of cholesterol metabolism. Results: The citrin-deficient group had a significantly higher high-density lipoprotein cholesterol (HDL-C) concentration than did the control group (78 ± 11 mg/dL vs 62 ± 14 mg/dL, P < 0.001), whereas the two groups had similar low-density lipoprotein cholesterol and triglyceride concentrations. The concentrations of markers of cholesterol synthesis (lathosterol and 7-dehydrocholesterol) and bile acids synthesis (7α-hydroxycholesterol and 27-hydroxycholesterol) were 1.5- to 2.8-fold and 1.5- to 3.9-fold, respectively, higher in the citrin-deficient group than in the control group. The concentration of 24S-hydroxycholesterol, a marker of cholesterol catabolism in the brain, was 2.5-fold higher in the citrin-deficient group. In both groups, the HDL-C concentration was significantly positively correlated with that of 27-hydroxycholesterol, the first product of the alternative bile acid synthesis pathway. Conclusions: HDL-C and sterol marker concentrations are elevated in citrin-deficient children post-NICCD. Moreover, cholesterol synthesis and elimination are markedly enhanced in the liver and brain of citrin-deficient children.

Medium-chain triglycerides supplement therapy with a low-carbohydrate formula can supply energy and enhance ammonia detoxification in the hepatocytes of patients with adult-onset type II citrullinemia.

Citrin, encoded by SLC25A13, constitutes the malate-aspartate shuttle, the main NADH-shuttle in the liver. Citrin deficiency causes neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2). Citrin deficiency is predicted to impair hepatic glycolysis and de novo lipogenesis, resulting in hepatic energy deficit. Secondary decrease in hepatic argininosuccinate synthetase (ASS1) expression has been considered a cause of hyperammonemia in CTLN2. We previously reported that medium-chain triglyceride (MCT) supplement therapy with a low-carbohydrate formula was effective in CTLN2 to prevent a relapse of hyperammonemic encephalopathy. We present the therapy for six CTLN2 patients. All the patients' general condition steadily improved and five patients with hyperammonemic encephalopathy recovered from unconsciousness in a few days. Before the treatment, plasma glutamine levels did not increase over the normal range and rather decreased to lower than the normal range in some patients. The treatment promptly decreased the blood ammonia level, which was accompanied by a decrease in plasma citrulline levels and an increase in plasma glutamine levels. These findings indicated that hyperammonemia was not only caused by the impairment of ureagenesis at ASS1 step, but was also associated with an impairment of glutamine synthetase (GS) ammonia-detoxification system in the hepatocytes. There was no decrease in the GS expressing hepatocytes. MCT supplement with a low-carbohydrate formula can supply the energy and/or substrates for ASS1 and GS, and enhance ammonia detoxification in hepatocytes. Histological improvement in the hepatic steatosis and ASS1-expression was also observed in a patient after long-term treatment.

Hypomorphic citrullinaemia due to mutated ASS1 with episodic ataxia.

Children with citrullinaemia commonly present in the neonatal period with life-threatening hyperammonaemia and progressive encephalopathy. Less often, 'hypomorphic' or mild late-onset childhood or adult-onset forms may be seen with intermittent neurological symptoms or acute crisis in pregnancy. We describe an 11-year-old boy with late-onset citrullinaemia manifesting as brief episodes of ataxia triggered by minor febrile illnesses, significant citrullinaemia, mild hyperammonaemia, normal neurological examination and mild cerebellar atrophy. Targeted gene sequencing showed a homozygous, missense mutation c.815G>A (p.R272H) in exon 12 of ASS1 gene resulting in the amino acid substitution of histidine for arginine at codon 272. Our case highlights the importance of recognising urea cycle defects as a cause of intermittent neurological symptoms such as ataxia. Type-1 citrullinaemia may remain hypomorphic and needs a high index of suspicion.