[Full-cycle, multidisciplinary and systematic management of citrin deficiency].

Professor Takeyori Saheki's team at Kagoshima University, Japan, published a paper in Nature Genetics in June 1999, pinpointing the pathogenic gene for adult-onset type Ⅱ citrullinemia as SLC25A13 and naming the protein product encoded by this gene as citrin. Over the past 25 years, the researches have made positive progress on the pathophysiological mechanism, clinical phenotype, molecular diagnosis, treatment, and prognosis of citrin deficiency (CD) as an autosomal recessive genetic disease. Currently, three age-dependent clinical phenotypes of CD have been found, namely neonatal intrahepatic cholestasis caused by citrin deficiency, failure to thrive and dyslipidemia caused by citrin deficiency, and adult-onset type Ⅱ citrullinemia. Although relevant internal medicine drugs are being researched and developed while liver transplantation has been used for the treatment of CD patients, scientific dietary therapy remains the foundation, core, and key for the management of this disease. Furthermore, CD management involves the full life cycle of patients, requiring the joint efforts of basic and clinical medicine as well as systematic articulation at multi-levels, such as the parents, family, and society. By full-cycle, multidisciplinary, and systematic management, it is an achievable goal for CD patients to learn, work, and live in a healthy manner.

[Analysis of the etiology and clinical indicators of infantile cholestasis].

Objective: To explore the disease spectrum and corresponding clinical indicators of infantile cholestasis so as to provide a basis for the diagnosis of this type of disease at an early stage. Methods: The clinical data was collected from 203 hospitalized children diagnosed with infantile cholestasis at the Department of Gastroenterology of Maternal and Child Health Care, Guiyang City, from January 2018 to March 2023, including 130 males and 73 females. Patients general condition, personal history, and blood biochemical test indicators, including liver and coagulation function, blood ammonia, blood lipid profile, blood sugar, TORCH, thyroid function, and others, were retrospectively analyzed after admission. Cholangiography and high-throughput gene sequencing were performed in certain patients. The etiology of the enrolled cases were analyzed. Children's clinical data were compared with distinct inherited metabolic liver diseases (Group A) and biliary atresia (Group B). The statistical analysis was conducted using the t-test, Mann-Whitney test, Kruskal-Wallis test, or χ2 test, according to different data. Results: In 33 cases, infectious factors-primarily CMV infection-were the etiology of cholestasis. Forty cases had aberrant bile duct development, primarily biliary atresia, choledochal cysts, and intrahepatic bile duct dysplasia. In 26 cases, genetic metabolic factors mainly included citrin protein deficiency, sodium-taurocholate co-transporting polypeptide deficiency, and Alagille syndrome. 11 cases had drug/poisoning factors (parenteral nutrition-associated cholestasis). 19 cases had idiopathic infantile cholestasis. Three cases had other factors; however, all of them had Kawasaki disease. 71 cases had an unclear diagnosis. There was no statistically significant difference in terms of gender and age between groups A and B (P>0.05). The alkaline phosphatase (ALP) and bile acid levels were significantly higher in Group A than Group B, with a P<0.05, while the gamma glutamyltransferase (GGT), direct bilirubin (DBil), and albumin levels were lower than those in Group B, with a P<0.05. The cytomegalovirus infection rate was higher in Group B (62.50%) than Group A (34.62%), and the difference between the two groups was statistically significant (χ2=3.89, P<0.05). The alanine aminotransferase, aspartate aminotransferase, GGT, DBil, and albumin were significantly lower in patients with citrin protein deficiency than those in patients with biliary atresia, while ALP, bile acid, and blood ammonia were higher than those in patients with biliary atresia. Patients with sodium-taurocholate co-transporting polypeptide deficiency had higher bile acid than patients with biliary atresia, while the DBil was lower than that in patients with biliary atresia, and the difference was statistically significant (P<0.05). Conclusion: Infantile cholestasis etiology is diverse. ALP, bile acids, GGT, DBil, and albumin levels can serve as simple indicators for early-stage differentiation between inherited metabolic liver disease and biliary atresia. The cholestasis etiology should be determined as early as possible following biliary atresia exclusion by actively completing genetic metabolic gene detection.

Serum procalcitonin as a marker of neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD).

BACKGROUND: Neonatal Intrahepatic Cholestasis (NICCD), as the early-age stage of Citrin deficiency involving liver dysfunction, lacks efficient diagnostic markers. Procalcitonin (PCT) has been identified as a biomarker for infection as well as various organ damage. This study aimed to explore the potential of PCT as a biomarker for NICCD. METHODS: In a single-center retrospective case-control study. Serum PCT concentrations before and after treatment of 120 NICCD patients, as the study group, were compared to the same number of cholestatic hepatitis patients, as the control group. The potential value of PCT to discriminate NICCD from control disease was further explored using Receiver Operating Characteristic (ROC) curve analysis and compared to those of other inflammatory markers. RESULTS: There was a significantly higher level of PCT in NICCD patients than in the control group. PCT concentrations were only weakly correlated with neutrophil counts and CRP levels (p ˂ 0.05). At a cut-off value of 0.495 ng/mL, PCT exhibited a significantly higher diagnostic value compared to other inflammatory markers for discriminating NICCD from the control, with a sensitivity of 90.8 % and specificity of 98.3 %. CONCLUSION: PCT might be used as an initial biomarker to discriminate children with NICCD from another hepatitis disease.

[Newborn screening, clinical features and genetic analysis for Citrin deficiency in Henan province].

OBJECTIVE: To explore the prevalence, clinical features, genetic characteristics and prognosis of Citrin deficiency in Henan province of China. METHODS: A total of 986 565 neonates screened by tandem mass spectrometry at the Third Affiliated Hospital of Zhengzhou University from January 2013 to December 2021 were retrospectively analyzed. Analysis of SLC25A13 gene variants and parental verification were carried out for neonates suspected for Citrin deficiency by next-generation sequencing. The clinical, biochemical and genetic characteristics of Citrin deficiency patients were integrated to guide the diet treatment and follow up the growth and development. Paired-t test was used to compare the amino acid levels in the peripheral blood samples before and after the treatment. RESULTS: Nine cases of Citrin deficiency were diagnosed among the 986 565 neonates. Specific elevation of citrulline was observed in all of the 9 cases. Six variants were detected by genetic sequencing, among which c.852_855delTATG, c.615+5G>A, c.550C>T and IVS16ins3kb were known pathogenic variants, whilst c.1111_1112delAT and c.837T>A were unreported previously. The detection rate for c. 852_855delTATG was the highest (61.6%, 11/18), followed by IVS16ins3kb (16.7%, 3/18). The clinical symptoms of all patients were relieved after the treatment, and the blood amino acid profile and biochemical parameters were significantly improved by gradually falling within the normal range. By June 2022, all patients had shown a good prognosis. CONCLUSION: The prevalence of Citrin deficiency among neonates from Henan Province by tandem mass spectrometry is 1/109 618, and the carrier rate for the pathogenic variants of the SLC25A13 gene was 1/166. The c.852_855delTATG may be a hot spot variant among the patients. Discovery of the novel variants has enriched the mutational spectrum of the SLC25A13 gene. Above results have provided a basis for the early diagnosis, treatment, prognosis and genetic counseling for the affected families.

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.

Adult-onset Type II Citrullinemia Developed under Dietary Restrictions during Imprisonment.

A 29-year-old man presented with liver damage, and a liver biopsy was performed, but the cause was unclear. Thereafter, he was referred to our hospital. We found that he had been unable to consume carbohydrates in his diet and preferred fried chicken since childhood. In addition, he had shown disturbance of consciousness and abnormal behavior while he had been in prison, where dietary intake had been restricted. A plasma amino acid analysis revealed hypercitrullinemia. Therefore, we suspected adult-onset type II citrullinemia (CTLN2). Genetic testing showed pathologic variations in the SLC25A13 gene, which allowed us to make a definite diagnosis of CTLN2.

Citrin deficiency due to SLC25A13 exon deletion in a Chinese infant: A case report.

INTRODUCTION: Citrin is a calcium-bound aspartate-glutamate carrier protein encoded by the gene SLC25A13, mutations of which can cause citrin deficiency, an autosomal recessive disorder. The manifestations of citrin deficiency include neonatal intrahepatic choledeposits caused by citrin deficiency (NICCD: OMIM#605814), intermediate growth disorders and dyslipidemia caused by citrin deficiency, and citrullinemia type II (OMIM#603471) in adults. NICCD is a classical metabolic disorder that causes cholestasis in newborns. PATIENT CONCERN AND CLINICAL FINDINGS: Here, we present the case of a 2-month-old male patient treated in our hospital on March 20, 2023, due to "postnatal skin xanthochromia and transaminases higher than normal values". Since birth, the child's skin had yellowed all over the body, and his condition did not improve after multiple medical treatments. DIAGNOSIS/INTERVENTION/OUTCOMES: The child underwent full exome gene testing at the age of 2 months and 13 days, and the results indicated heterozygous deletion of exon 3 of the SLC25A13 gene, while genetic testing of the parents revealed no gene mutations. The variant was preliminarily judged as being pathogenic according to the ACMG guidelines, and the patient was diagnosed with "citrin deficiency". Skin yellowing eventually subsided, and liver function returned to normal without special treatment. CONCLUSIONS: Here, we report a rare case of citrin deficiency caused by a heterozygous deletion of the SLC25A13 gene. This case increases the clinical phenotypic profile of NICCD, suggesting that clinicians must be vigilant regarding such genetic metabolic diseases in the clinic for early diagnosis and treatment. NICCD should always be considered in the differential diagnosis of neonatal cholestasis.

[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.

Features of liver injury in 138 Chinese patients with NICCD.

OBJECTIVES: To find biochemical and molecular markers can assist in identifying serious liver damage of neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD) patients. METHODS: 138 patients under 13 days to 1.1 year old diagnosed of NICCD in our center from 2004 to 2020. Base on the abnormal liver laboratory tests, we divided 138 patients into three groups: acute liver failure (ALF), liver dysfunction, and non-liver dysfunction groups, then compared their clinical, biochemical and, molecular data. RESULTS: 96 % of 138 patients had high levels of citrulline and high ratio of threonine to serine, which is the distinctive feature of plasma amino acid profile for NICCD. A total of 18.1 % of 138 patients had evidence of ALF who presented the most severity hepatic damage, 51.5 % had liver dysfunction, and the remaining 30.4 % presented mild clinical symptoms (non-liver dysfunction). In ALF group, the levels of citrulline, tyrosine, TBIL, ALP, and γ-GT was significantly elevated, and the level of ALB and Fisher ratio was pronounced low. Homozygous mutations of 1,638_1660dup, IVS6+5G.A, or IVS16ins3kb in SLC25A13 gene were only found in ALF and liver dysfunction groups. Supportive treatment including medium-chain triglyceride supplemented diet and fresh frozen plasma could be life-saving and might reverse ALF. CONCLUSIONS: High level of citrulline, tyrosine, TBIL, ALP, γ-GT, and ammonia, low level of albumin, and low Fisher ratio were predictors to suggest severe liver damage in NICCD patients who may go on to develop fatal metabolic disorder. Early identification and proper therapy is particularly important for these patients.

Genetic and clinical features of patients with intrahepatic cholestasis caused by citrin deficiency.

OBJECTIVES: Citrin deficiency (CD) is an autosomal recessive disease caused by mutations of the SLC25A13 gene, plasma bile acid profiles detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) could be an efficient approach for early diagnosis of intrahepatic cholestasis. The aim of this study was to investigate the genetic testing and clinical characteristics of a series of patients with CD, and to analyse plasma bile acid profiles in CD patients. METHODS: We retrospectively analysed data from 14 patients (12 males and 2 females, age 1-18 months, mean 3.6 months) with CD between 2015 and 2021, including demographics, biochemical parameters, genetic test results, treatment, and clinical outcomes. In addition, 30 cases (15 males and 15 females, age 1-20 months, mean 3.8 months) with idiopathic cholestasis (IC) served as a control group. Plasma 15 bile acid profiles were compared between the CD and IC groups. RESULTS: Eight different mutations of the SLC25A13 gene were detected in the 14 patients diagnosed with CD, of which three novel variants of the SLC25A13 gene were investigated, the c.1043C>T (p.P348L) in exon11, the c.1216dupG (p.A406 Gfs*13) in exon12 and the c.135G>C (p.L45F) in exon3. More than half of the patients with CD had prolonged neonatal jaundice, which was associated with significantly higher alpha-fetoprotein (AFP) levels, hyperlactatemia and hypoglycemia. The majority of patients were ultimately self-limited. Only one patient developed liver failure and died at the age of 1 year due to abnormal coagulation function. In addition, the levels of glycochenodeoxycholic acid (GCDCA), taurocholate (TCA), and taurochenodeoxycholic acid (TCDCA) were significantly increased in the CD group compared with those in the IC group. CONCLUSIONS: Three novel variants of the SLC25A13 gene were identified for the first time, providing a reliable molecular reference and expanding the SLC25A13 gene spectrum in patients with CD. Plasma bile acid profiles could be a potential biomarker for non-invasive early diagnosis of patients with intrahepatic cholestasis caused by CD.

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.

Hyperammonemia in a pregnant woman with citrullinemia type I: a case report and literature review.

BACKGROUND: Citrullinemia type I (CTLN1) is a rare urea cycle disorder (UCD) with few adult cases described so far. Diagnosis of late-onset CTLN1 is difficult, and delayed treatment may increase the risk of severe hyperammonemia. Pregnancy is an important risk factor for women with CTLN1. However, the clinical manifestations of CTLN1 in a pregnant woman may be mistaken for pregnancy side effects and ultimately delay a timely diagnosis. CASE PRESENTATION: A 34-year-old woman developed vomiting and disturbance of consciousness after 12 weeks of gestation. A blood test showed hyperammonemia (454 µg/dL) with normal liver function tests. She fell into a deep coma, and her serum ammonia level increased to 800 µg/dL. Continuous renal replacement therapy (CRRT) was administered as a diagnostic treatment for UCD and serum ammonia. This patient's case was complicated by co-infection; her dependents decided to withdraw life support and the patient died. She was diagnosed with CTLN1 by analyses of plasma amino acids, urinary orotic acid, and second-generation gene sequencing. DISCUSSION AND CONCLUSION: When a patient displays symptoms of emesis and disturbance of consciousness in early pregnancy, blood ammonia should be monitored, and UCD should be considered, particularly for patients with hyperammonemia in the absence of severe liver function abnormalities.

Improved diagnosis of citrin deficiency by newborn screening using a molecular second-tier test.

BACKGROUND: Citrin deficiency is an autosomal recessive disorder caused by variants of the SLC25A13 gene. Although newborn screening (NBS) provides an opportunity for its early diagnosis and treatment, citrin deficiency detection rates remain lower than those estimated. METHODS: Before 2018, NBS for citrin deficiency was based on citrulline levels alone. In June 2018, a second-tier molecular test was implemented to detect 11 common variants of the SLC25A13 gene and improve the NBS detection rates. This study compares the incidence rates and costs before and after the second-tier implementation. RESULTS: Prior to 2018, five subjects were diagnosed via NBS, and 12 of 555,449 newborns screened were missed. In comparison, 11 subjects were diagnosed out of 198,071 newborns screened after 2018, and there were no false-negatives. The citrin deficiency detection rate increased from 1/32,673 to 1/18,006 after the second-tier test was implemented, with only a minimal increase in the total cost. The number of false-positive in our cohort was tolerable. Subjects with citrin deficiency may present with borderline elevated citrulline levels; these can remain slightly elevated or increase considerably on retest. Four patients (80%) detected prior to second-tier testing and six patients (55%) detected after it was implemented were identified based on the citrulline levels alone. However, at the time of second blood sampling, the normal citrulline level of five subjects did not exclude a citrin deficiency diagnosis. CONCLUSIONS: Our study shows that it is vital and cost-effective to employ second-tier molecular testing to improve the detection of citrin deficiency by NBS.

Asymptomatic ASS1 carriers with high blood citrulline levels.

INTRODUCTION: Citrullinemia Type 1 (CTLN1) is an autosomal recessive disorder caused by variants in the ASS1 gene. This study intends to clarify the etiology of false positives in newborn screening for citrullinemia. METHOD: Newborns who had elevated dried-blood spot citrulline levels were enrolled, and medical records were reviewed retrospectively. Common ASS1 variants were screened using high-resolution melting analysis. RESULT: Between 2011 and 2021, 130 newborns received confirmatory testing for citrullinemia, 4 were found to be patients for CTLN1; 11 were patients with citrin deficiency; and 49 newborns were confirmed to be carrying one pathogenic ASS1 variant. The incidence of CTLN1 was 1 in 188,380 (95% confidence interval: 1 in 73,258 to 1 in 484,416). All ASS1 variants studied in this cohort were located in exons 11 to 15, which encode the tetrameric interface regions of the ASS1 protein. Among 10 ASS1 carriers with elevated citrulline levels and complete sequence data, four (40%) revealed additional non-benign ASS1 variants; in contrast, only 2 of the 26 controls (7.7%), with normal citrulline levels, had additional ASS1 variants. CONCLUSION: Heterozygote ASS1 variants may lead to a mild elevation of blood citrulline levels: about 2-6 times the population mean. Molecular testing and family studies remain critical for precise diagnosis, genetic counseling, and management.

Clinical manifestation and long-term outcome of citrin deficiency: Report from a nationwide study in Japan.

Citrin deficiency is an autosomal recessive disorder caused by mutations in the SLC25A13 gene. The disease can present with age-dependent clinical manifestations: neonatal intrahepatic cholestasis by citrin deficiency (NICCD), failure to thrive, and dyslipidemia by citrin deficiency (FTTDCD), and adult-onset type II citrullinemia (CTLN2). As a nationwide study to investigate the clinical manifestations, medical therapy, and long-term outcome in Japanese patients with citrin deficiency, we collected clinical data of 222 patients diagnosed and/or treated at various different institutions between January 2000 and December 2019. In the entire cohort, 218 patients were alive while 4 patients (1 FTTDCD and 3 CTLN2) had died. All patients <20 years were alive. Patients with citrin deficiency had an increased risk for low weight and length at birth, and CTLN2 patients had an increased risk for growth impairment during adolescence. Liver transplantation has been performed in only 4 patients (1 NICCD, 3 CTLN2) with a good response thereafter. This study reports the diagnosis and clinical course in a large cohort of patients with citrin deficiency and suggests that early intervention including a low carbohydrate diet and MCT supplementation can be associated with improved clinical course and long-term outcome.

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.

Citrin deficiency ­ pathogenesis, clinical and biochemical manifestation, diagnostics, treatment / Deficyt cytrynu.

Citrin deficiency is an inherited metabolic disease caused by biallelic pathogenic variants in the SLC25A13 gene encoding the carrier protein called citrin. There are observed three characteristic clinical and biochemical age-dependent phenotypes: neonatal intrahepatic cholestasis caused by citrin deficiency, failure to thrive and dyslipidemia caused by citrin deficiency and adult-onset citrullinemia type 2. The paper presents the characteristics of the pathogenesis of citrin deficiency, clinical and biochemical delineation of individual phenotypes, differential diagnosis and treatment of citrin deficiency.

In-house multiplex ligation-dependent probe amplification assay for citrin deficiency: analytical validation and novel exonic deletions in SLC25A13.

Citrin deficiency is one of the most common inborn errors of metabolism in East Asians, which may manifest as neonatal cholestasis, failure to thrive and dyslipidaemia, or recurrent hyperammonaemic encephalopathy. Its molecular diagnosis requires confirmation of the presence of biallelic pathogenic variants in SLC25A13 gene by sequencing, and analysis for a common insertion IVS16ins3kb. However, patients with compatible biochemical features but only one monoallelic pathogenic variant have remained a diagnostic challenge. Here we report the development, validation and application of a multiplex ligation-dependent probe amplification (MLPA) assay using an in-house oligonucleotide probemix and a customised Coffalyer.NET worksheet for detection of exonic copy number variations in SLC25A13. With this MLPA assay, we successfully identified the presence of a heterozygous exonic deletion in SLC25A13 in three of 15 (20%) unrelated individuals with only one monoallelic pathogenic variant detected using conventional methods. Three exonic deletions, two novel involving exon 14 and one reported involving exon 5, were subsequently confirmed with Sanger sequencing. In summary, we developed, evaluated, and demonstrated the clinical utility of an in-house MLPA assay to look for exonic deletions in SLC25A13 in patients with citrin deficiency. With the discovery of novel deletions, MLPA should be considered a test of choice for molecular diagnosis of citrin deficiency when the sequencing result is inconclusive.