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Urea cycle defects (UCDs) are severe inherited metabolic diseases with high unmet needs which present a permanent risk of hyperammonaemic decompensation and subsequent acute death or neurological sequelae, when treated with conventional dietetic and medical therapies. Liver transplantation is currently the only curative option, but has the potential to be supplanted by highly effective gene therapy interventions without the attendant need for life‐long immunosuppression or limitations imposed by donor liver supply. Over the last three decades, pioneering genetic technologies have been explored to circumvent the consequences of UCDs, improve quality of life and long‐term outcomes: adenoviral vectors, adeno‐associated viral vectors, gene editing, genome integration and non‐viral technology with messenger RNA. In this review, we present a summarised view of this historical path, which includes some seminal milestones of the gene therapy's epic. We provide an update about the state of the art of gene therapy technologies for UCDs and the current advantages and pitfalls driving future directions for research and development. [ABSTRACT FROM AUTHOR]

Abstract Glycerol phenylbutyrate (GPB) is an ammonia scavenger drug commonly used in the therapy of patients with urea cycle defects. Reported side effects include body odor, abdominal pain, nausea, burning sensation in mouth, vomiting, and heartburn. We report on a 3‐year‐old late diagnosed female patient with ornithine transcarbamylase deficiency that experienced severe loss of appetite under treatment with GBP. Due to catabolism (calory intake about 400 kcal/day) and the associated risk of metabolic decompensation, GBP treatment was discontinued. Her appetite and eating behavior normalized within 1 day after discontinuation of GBP and switch to sodium benzoate. Our case demonstrates that GBP can cause severe loss of appetite that may put patients at risk of metabolic decompensation and require discontinuation of therapy.

An infant presented with recurrent episodes of encephalopathy, responding to nonspecific management of sepsis. High index of suspicion helped uncover underlying error of metabolism. [ABSTRACT FROM AUTHOR]

Objective: Inborn errors of metabolisms (IEMs) are a heterogeneous group of disorders that can occur as a result of inherited or spontaneous mutations, are rare when considered alone, but have many diseases as a group. Although they are generally thought of as diseases of the neonatal period, 50% of these also occur outside the neonatal period, and some are not diagnosed until adulthood. The aim of this study is to examine the frequency, clinical and laboratory features of inborn errors of metabolism in the neonatal period. Methods: The results of 60 patients who were diagnosed with IEMs as a result of the study, out of 1400 patients who were followed up and treated in the Children's Hospital Neonatal Intensive Care Unit between January 2018 and December 2020, were evaluated. Results: In this study, it consisted of 60 cases, 30 (%50) of which were girls and 30 (%50) were boys (50%). The median age of the patients included in the study was 3 (1-25) days at admission, median weight was 3100 (1000-4000) g, and gestational week was found to be median 39 (27-40) weeks at admission. The most common complaints were feeding difficulty 43(72%), tachypnea 27 (45%) and vomiting 5 (8.3%). The most common laboratory findings were metabolic acidosis 39 (65%) and 36 (60%) hypoglycemia. There was a history of consanguinity in 46 (76.6%) cases, and a history of sibling death in 30 (50%). The mother had a history of abortion in 5 (8.3%) patients who did not have a history of sibling death. The most common diagnoses were Urea cycle disorder 13 (21.7%), organic acidemia 12 (20%), galactosemia 10 (16.7%) and amino acid metabolism disorders 9 (15%). Conclusion: Inborn errors of metabolisms, which are a group of diseases that can occur in different spectrums with clinical, biochemical and genetic heterogeneity, should be kept in mind especially in regions where consanguineous marriages are high. In cases such as metabolic acidosis, which presents with nonspecific symptoms such as malnutrition, tachypnea and jaundice in the neonatal period and cannot be explained in laboratory examinations, care should be taken and they should be referred to centers for further investigation. [ABSTRACT FROM AUTHOR]

Abstract Background Neonatal intrahepatic cholestasis caused by citrin deficiency (CD) is a rare inborn error of metabolism due to variants in the SLC25A13 gene encoding the calcium-binding protein citrin. Citrin is an aspartate-glutamate carrier located within the inner mitochondrial membrane. Case presentation We report on two siblings of Romanian-Vietnamese ancestry with citrin deficiency. Patient 1 is a female who presented at age 8 weeks with cholestasis, elevated lactate levels and recurrent severe hypoglycemia. Diagnosis was made by whole exome sequencing and revealed compound heterozygosity for the frameshift variant c.852_855del, p.Met285Profs*2 and a novel deletion c.(69 + 1_70–1)_(212 + 1_231–1)del in SLC25A13. The girl responded well to dietary treatment with a lactose-free, MCT-enriched formula. Her younger brother (Patient 2) was born 1 year later and also found to be carrying the same gene variants. Dietary treatment from birth was able to completely prevent clinical manifestation until his current age of 4.5 months. Conclusions As CD is a well-treatable disorder it should be ruled out early in the differential diagnosis of neonatal cholestasis. Due to the combination of hepatopathy, lactic acidosis and recurrent hypoglycemia the clinical presentation of CD may resemble hepatic mitochondrial depletion syndrome.

The urea cycle generates arginine that is one of the major precursors for creatine biosynthesis. Here we evaluate levels of creatine and guanidinoacetate (the precursor in the synthesis of creatine) in plasma samples (ns = 207) of patients (np = 73) with different types of urea cycle disorders (ornithine transcarbamylase deficiency (ns = 22; np = 7), citrullinemia type 1 (ns = 60; np = 22), argininosuccinic aciduria (ns = 81; np = 31), arginase deficiency (ns = 44; np = 13)). The concentration of plasma guanidinoacetate positively correlated (p

Urea cycle disorders (UCDs) are a group of rare inherited metabolic diseases causing hyperammonemic encephalopathy. Despite intensive dietary and pharmacological therapy, outcome is poor in a subset of UCD patients. Reducing ammonia production by changing faecal microbiome in UCD is an attractive treatment approach. We compared faecal microbiome composition of 10 UCD patients, 10 healthy control subjects and 10 phenylketonuria (PKU) patients. PKU patients on a low protein diet were included to differentiate between the effect of a low protein diet and the UCD itself on microbial composition. Participants were asked to collect a faecal sample and to fill out a 24 h dietary journal. DNA was extracted from faecal material, taxonomy was assigned and microbiome data was analyzed, with a focus on microbiota involved in ammonia metabolism.In this study we show an altered faecal microbiome in UCD patients, different from both PKU and healthy controls. UCD patients on dietary and pharmacological treatment had a less diverse faecal microbiome, and the faecal microbiome of PKU patients on a protein restricted diet with amino acid supplementation showed reduced richness compared to healthy adults without a specific diet. The differences in the microbiome composition of UCD patients compared to healthy controls were in part related to lactulose use. Other genomic process encodings involved in ammonia metabolism, did not seem to differ. Since manipulation of the microbiome is possible, this could be a potential treatment modality. We propose as a first next step, to study the impact of these faecal microbiome alterations on metabolic stability. Take home message: The faecal microbiome of UCD patients was less diverse compared to PKU patients and even more compared to healthy controls.

Cytotoxic lesions of the corpus callosum (CLOCCs) are secondary lesions associated with entities like infection manifested by restricted diffusion on diffusion-weighted cranial magnetic resonance imaging. Our objectives are to evaluate the clinic-radiological spectrum of pediatric patients with cytotoxic lesions of the corpus callosum (CC). Children (0–18 years) admitted between February 2017 and May 2020 with splenial lesions showing diffusion restriction on MRI, either isolated or within involvement of other parts of the brain, were included retrospectively. The primary lesions of the CC (e.g. acute disseminated encephalomyelitis, acute ischemic infarction, and glioblastoma multiforme) were excluded. CLOCCs were divided into infection-associated, metabolic disorder–associated, and trauma-associated lesions, as well as CLOCCs involving other entities. Data were collected from the medical databases. Forty-one patients were determined to have CLOCCs. Twenty-five (61%) were infection-associated, nine (22%) were trauma-associated, and three (7%) were metabolic disorder–associated cases, including 2 inherited disorders of metabolism. There were four (10%) patients with other entities, three with epilepsy, and one had an apparent life-threatening event. Six patients had a known etiology among the infection-associated group; one had multisystem inflammatory syndrome caused by COVID-19 and one had been infected by COVID-19 without any complications. All the infection-associated patients with isolated splenial lesions recovered totally, although six patients required intensive care hospitalization. Four trauma-associated patients had sequela lesions. CLOCCs are associated with a spectrum of diseases, including the new coronavirus, COVID-19 infection. Infection-associated CLOCCs has the best prognosis, although severe cases may occur. Sequelae are possible based on the etiology. [ABSTRACT FROM AUTHOR]

Background: HHH syndrome is a rare autosomal recessive disorder of the urea cycle, caused by a deficient mitochondrial ornithine transporter. We report the first successful liver transplantation in HHH syndrome performed in a seven‐year‐old boy. The patient presented at 4 weeks of age with hyperammonemic coma. The plasma amino acid profile was suggestive of HHH syndrome, and the diagnosis was confirmed when sequencing of the SLC25A15 gene identified two mutations p.R275Q and p.A76D. Although immediate intervention resulted in normalization of plasma ammonia levels within 24 hours, he developed cerebral edema, coma, convulsions, and subsequent neurological sequelae. Metabolic control was difficult requiring severe protein restriction and continued treatment with sodium benzoate and L‐arginine. Despite substantial developmental delay, he was referred to our center for liver transplantation because of poor metabolic control. Following cadaveric split liver transplantation, there was complete normalization of his plasma ammonia and plasma amino acid levels under a normal protein‐containing diet. This excellent metabolic control was associated with a markedly improved general condition, mood and behavior, and small developmental achievements. Twelve years after liver transplantation, the patient has a stable cognitive impairment without progression of spastic diplegia. Conclusion: This first case of liver transplantation in HHH syndrome demonstrates that this procedure is a therapeutic option for HHH patients with difficult metabolic control. [ABSTRACT FROM AUTHOR]

Argininemia is an autosomal recessive urea cycle disorder caused by the deficiency of arginase. Our first case presented with psychomotor retardation, difficulty of walking, and progressive tiptoeing. Laboratory investigations revealed mildly elevated hepatic enzymes and elevated plasma arginine concentration. Molecular genetic analysis was performed for suspected argininemia and a novel homozygous mutation c. 231C> A (p. S77R) was detected in the ARG1 gene. The second patient was admitted because of poor head control when he was aged 6 months. Microcephaly was detected in his physical examination, and basic metabolic tests were studied. Elevated levels of plasma arginine and orotic acid in urine organic acid analysis were compatible with argininemia. A homozygous mutation c.703G> C (p. G235R) was detected in the ARG1 gene and the diagnosis was confirmed. Arginineemia is a rare cause of progressive spastic diplegia. Patients may be mistakenly diagnosed as having cerebral palsy. Microcephaly may be the initial clinical finding of the disorder.

Glycine conjugation is an important phase II reaction and represents a central detoxification pathway which is essential for the recycling of free coenzyme A. Only few sequence variants have been reported in the human GLYAT gene and only two studies have overexpressed the human protein in bacterial systems and partially characterized it. This has prompted us to study the wild-type enzyme and two sequence variants not only in the E. coli strain Origami 2(DE3), but also to overexpress GLYAT in HEK293 cells, a human-derived cell line. Following purification of the recombinant proteins from E. coli the wild-type GLYAT protein and sequence variants, p.(Gln61Leu) yielded decreased specific activity than the wild-type enzyme, while specific activity of p.(Asn156Ser) activity of the latter variant was somewhat increased. K M values were similar for the three forms of GLYAT overexpressed in bacteria and for the wild-type enzyme overexpressed in HEK293 cells. Localization studies demonstrated intramitochondrial localization of human wild-type GLYAT, conjugated with eGFP, in the HEK293 cells. As p.(Gln61Leu) does not only impair GLYAT activity in vitro , but is of high prevalence in a Caucasian Afrikaner cohort in South Africa, potential pharmacogenetic implications, warrant further studies of GLYAT. [ABSTRACT FROM AUTHOR]

Objective: Hyperargininemia due to Arginase 1 deficiency is a rare inborn error of the urea cycle with an incidence estimated at 1:950 000. It has typical severe and progressive abnormal neurological features with biochemical findings of hyperargininemia and hyperexcretion of orotic acid. The aim of our study is to review the clinical and biochemical presentations of 4 children diagnosed with Arginase 1 deficiency in Malaysia and compare with the literature review. Design and Methods: We retrospectively reviewed the medical records of 4 patients with molecularly confirmed Arginase 1 deficiency. Patients were identified from a selective high-risk screening of 51 682 symptomatic patients from January 2006 to December 2020. Results: Our patients exhibited heterogeneous clinical presentations with acute and progressive neurological abnormalities and varying degrees of plasma arginine and urine orotic acid excretions. Interestingly, an unusual hyperexcretion of homocitrulline was found in 3 patients. Conclusions: Hyperargininemia due to Arginase 1 deficiency can present acutely and hyperexcretion of homocitrulline can be an additional biochemical feature of Arginase 1 deficiency. [ABSTRACT FROM AUTHOR]

Citrullinaemia is a urea cycle defect that results from a deficiency of the enzyme arginosuccinate synthetase. Type 1 disease is diagnosed in childhood, whereas type 2 disease is adult onset. But, we report the outcome in a boy (13 years) with citrullinaemia type 2 who received a live donor liver transplant (LDLT) at our centre. One advantage of LDLT over deceased donor liver transplantation is the opportunity to schedule surgery, which beneficially affects neurological consequences. In conclusion, transplantation should be considered to be the definitive treatment for citrullinaemia type 2 at this stage, although some issues remain unresolved. [ABSTRACT FROM AUTHOR]

Abstract Excess urinary orotic acid excretion occurs in patients with some inborn errors of metabolic pathways such as pyrimidine synthesis and urea cycle. Thus, rapid diagnosis of orotic aciduria has a vital importance for patients. In this paper, a novel method for determination of orotic acid in urine samples by ion chromatography with suppressed conductivity detection was investigated. The separation of orotic acid from urine matrix was accomplished by using an anion exchange column with optimized isocratic eluent program which utilized 50 mM NaOH. The other chromatographic conditions were as follows: the suppressor current was 31 mA; the flow rate of mobile phase was 0.25 mL min−1; the column temperature was 30 °C; sample loop volume was 10 μL. Under optimized conditions, the limit of detection was 0.2 μmol L‾1. Dramatically elevated orotic acid concentration was observed on pathological urine samples comparing to healthy urines, as expected. There are a good many advantages of the proposed method, but using an environmentally friendly reagent free system, no organic solvent employment and its quick nature, and being a sensitive and reliable method are the most obvious ones. The proposed method, therefore, may be utilized as an alternative technique for clinical laboratories. Highlights • Fast and reliable orotic acid analysis in urine is vital for children. • A new IC-CD method was developed and validated for orotic acid in human urine. • RF-IC method is rapid, cheap, precise and reliable. • The proposed method is convenient for the relevant clinical laboratories. [ABSTRACT FROM AUTHOR]

Argininemia is an autosomal recessive urea cycle disorder caused by the deficiency of arginase. Our first case presented with psychomotor retardation, difficulty of walking, and progressive tiptoeing. Laboratory investigations revealed mildly elevated hepatic enzymes and elevated plasma arginine concentration. Molecular genetic analysis was performed for suspected argininemia and a novel homozygous mutation c. 231C> A (p. S77R) was detected in the ARG1 gene. The second patient was admitted because of poor head control when he was aged 6 months. Microcephaly was detected in his physical examination, and basic metabolic tests were studied. Elevated levels of plasma arginine and orotic acid in urine organic acid analysis were compatible with argininemia. A homozygous mutation c.703G>C (p. G235R) was detected in the ARG1 gene and the diagnosis was confirmed. Arginineemia is a rare cause of progressive spastic diplegia. Patients may be mistakenly diagnosed as having cerebral palsy. Microcephaly may be the initial clinical finding of the disorder. [ABSTRACT FROM AUTHOR]

Citrullinemia or ASS deficiency in its classical form presents in the neonatal period with poor feeding, hyperammonemia, encephalopathy, seizures, and if untreated can be fatal. Despite advances in medical therapy, neurocognitive outcomes remain suboptimal. LT has emerged as a potential management option. A retrospective singlecenter review identified 7 children with a median age of 1.1 years (range, 0.6-5.8) at referral. Five children presented clinically, and 2 were treated prospectively from birth due to positive family history. All patients received standard medical and dietary therapy prior to LT. The indications for LT were frequent metabolic decompensations in 4, elective in 2, and ALF in 1. The median age at LT was 2.4 years (range, 1.3-6.5). Five patients received 6 left lateral segment grafts, one a live unrelated donor left lateral segment as an APOLT graft, and one a cadaveric whole liver graft as APOLT. One child required retransplantation due to hepatic artery thrombosis. Graft and patient survival were 86% and 100%, respectively. Median follow-up is 3.1 years (range, 0.1-4.1), and the median age at follow-up is 5.5 years (range, 4.0-9.8). There have been no metabolic decompensations in 6 children, while 1 patient (with APOLT) developed asymptomatic hyperammonemia with no clinical or histological signs of liver injury, requiring additional medical therapy. Our medium-term experience following LT in citrullinemia is favorable, demonstrating a positive transformation of the clinical phenotype. [ABSTRACT FROM AUTHOR]

Summary Inborn urea cycle disorders are under-recognised metabolic causes of hyperammonemia in adults. A 28-year-old primigravida, seven weeks pregnant, affected by hyperemesis gravidarum developed acute liver injury (ALI) and then acute liver failure (ALF) in less than 48 h. Because the patient developed atypical features, especially mildly elevated aminotransferases contrasting with very high blood ammonia levels (281 μmol/L), concomitant with normal serum creatinine, an inborn error of metabolism was suspected. We performed emergency metabolic analyses, stopped all protein intake and started with intravenous (i.v.) high caloric intake, nitrogen scavenger drugs and haemodialysis. The neurological and hepatic status of the patient quickly improved together with normalisation of her ammonemia levels. High plasma glutamine and urinary orotic acid, alongside low plasma arginine, citrulline and ornithine were suggestive of an ornithine transcarbamylase deficiency, later confirmed by molecular analyses. Foetal sex was female, as determined by foetal DNA analysis in maternal blood, and foetal development was unremarkable throughout the pregnancy. Delivery was induced at 39 weeks with a close monitoring of ammonemia levels and i.v. perfusion of carbohydrates and lipids during labour and immediately post-partum to avoid hypercatabolism. Delivery was uneventful and the patient delivered a healthy female baby. Urea cycle disorders should be contemplated in non-jaundiced patients with ALI or ALF, severe hyperammonemia and normal serum creatinine regardless of serum aminotransferase levels. The prompt recognition of this rare condition and the rapid initiation of adequate metabolic therapy are mandatory to prevent irreversible neurological sequelae and to avoid liver transplantation. [ABSTRACT FROM AUTHOR]

Citrullinemia Type 1 (also known as classic citrullinemia) is a rare autosomal recessive urea cycle disorder due to reduced activity of argininosuccinate synthetase 1; characterized by hyperammonemia leading to neurological damage. The authors report a case of an 8-y boy who was diagnosed with Citrullinemia Type 1 at birth which was anticipated prenatally due to family history. His diagnosis was confirmed as a homozygous mutation (Exon 15: c.1168G > A (p.G390R)) of ASS gene. Inspite of being on a protein-free diet and ammonia scavenging treatment; the patient developed recurrent episodes of encephalopathy and seizures; complicated with behavioral issues. The patient underwent living related liver-transplantation from his mother (heterozygous carrier of the same mutation). Peri-transplant management of ammonia and plasma amino acid levels is challenging and has been highlighted. It is important to consider liver transplantation as it corrects the genetic deficiency of ASS resulting in the reversal of neuro-behavioral changes, as was seen in index patient. [ABSTRACT FROM AUTHOR]

Background The hepatic urea cycle is the main metabolic pathway for detoxification of ammonia. Inborn errors of urea cycle function present with severe hyperammonemia and a high case fatality rate. Long-term prognosis depends on the residual activity of the defective enzyme. A reliable method to estimate urea cycle activity in-vivo does not exist yet. The aim of this study was to evaluate a practical method to quantify 13 C-urea production as a marker for urea cycle function in healthy subjects, patients with confirmed urea cycle defect (UCD) and asymptomatic carriers of UCD mutations. Methods 13 C-labeled sodium acetate was applied orally in a single dose to 47 subjects (10 healthy subjects, 28 symptomatic patients, 9 asymptomatic carriers). Results The oral 13 C-ureagenesis assay is a safe method. While healthy subjects and asymptomatic carriers did not differ with regards to kinetic variables for urea cycle flux, symptomatic patients had lower 13 C-plasma urea levels. Although the 13 C-ureagenesis assay revealed no significant differences between individual urea cycle enzyme defects, it reflected the heterogeneity between different clinical subgroups, including male neonatal onset ornithine carbamoyltransferase deficiency. Applying the 13 C-urea area under the curve can differentiate between severe from more mildly affected neonates. Late onset patients differ significantly from neonates, carriers and healthy subjects. Conclusion This study evaluated the oral 13 C-ureagenesis assay as a sensitive in-vivo measure for ureagenesis capacity. The assay has the potential to become a reliable tool to differentiate UCD patient subgroups, follow changes in ureagenesis capacity and could be helpful in monitoring novel therapies of UCD. [ABSTRACT FROM AUTHOR]

Acute focal neurologic deficits are a rare but known presentation of ornithine transcarbamylase deficiency, particularly in females. We describe here a 6-year-old girl with newly diagnosed ornithine transcarbamylase deficiency who presents with an episode of acute cortical blindness lasting for 72 hours in the absence of hyperammonemia. Her symptoms were associated with a subcortical low-intensity lesion with overlying cortical hyperintensity on fluid-attenuated inversion recovery magnetic resonance imaging (MRI) of the occipital lobes. Acute reversible vision loss with these MRI findings is an unusual finding in patients with ornithine transcarbamylase deficiency. Our findings suggest a role for oxidative stress and aberrant glutamine metabolism in the acute clinical features of ornithine transcarbamylase deficiency even in the absence of hyperammonemia. [ABSTRACT FROM PUBLISHER]

Hyperammonemia occurs frequently in the critically ill but is largely confined to patients with hepatic dysfunction or failure. Non-hepatic hyperammonemia (NHHA) is far less common but can be a harbinger of life-threatening diagnoses that warrant timely identification and, sometimes, empiric therapy to prevent seizures, status epilepticus, cerebral edema, coma and death; in children, permanent cognitive impairment can result. Subsets of patients are at particular risk for developing NHHA, including the organ transplant recipient. Unique etiologies include rare infections, such as with Ureaplasma species, and unmasked inborn errors of metabolism, like urea cycle disorders, must be considered in the critically ill. Early recognition and empiric therapy, including directed therapies towards these rare etiologies, is crucial to prevent catastrophic demise. We review the etiologies of NHHA and highlight the first presentation of it associated with a concurrent Ureaplasma urealyticum and Mycoplasma hominis infection in a previously healthy individual with polytrauma. Based on this clinical review, a diagnostic and treatment algorithm to identify and manage NHHA is proposed., Competing Interests: Declaration of Competing Interest None., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Introduction: The development in therapeutic strategies has increased survival of children affected by inborn errors of metabolism with restricted diet (IEMRD). These diseases have mild- and long-term consequences on the health. Little is known about the impact on the quality of life (QoL) of children and their families. The aims of this study were: to compare the QoL of the children and parents affected by IEMRD with the QoL of the general population and one pathology associated with long-term consequences. Patients and methods: This cross-sectional study was performed at the French Reference Center for inborn metabolic disorders (Marseille, France). Inclusion criteria were: a child with a diagnosis of organic aciduria, urea cycle defect, or maple syrups urine disease (MSUD). Socio-demographics, clinical data, and QoL were recorded. Results: Twenty-one of 32 eligible families were included during a planned routine visit. Ten (47%, 95% CI 27-69%) children were affected by organic aciduria, six (29%, 95% CI 10-48%) by urea cycle defects, and five (24%, 95% CI 6-42%) by MSUD. Among the younger children, the general well-being was significantly lower in the children with IEMRD than in the leukemia children (58 ± 16 versus 76 ± 15, p = 0.012), and among the older children, the leisure activities were significantly lower in the children with IEMRD than in the leukemia children (29 ± 18 versus 62 ± 22, p < 10-3), while the relationships with teachers were better (76 ± 23 versus 60 ± 23, p = 0.01). The physical QoL score was lower in the parents than in the French norms (66 ± 21 versus 75 ± 1, p = 0.05). Factors modulating QoL were: eating and neurologic disorders, enteral nutrition, and feeding modalities. Conclusion: The children and the parents of children affected presented altered 'physical' and 'social' QoL scores compared with the norms and patients with leukemia and their families. Future studies based on larger cohort studies should determine the different weights of potential predictive factors of QoL. Keywords: Inborn errors of metabolism with restricting dietary, Organic aciduria, Urea [ABSTRACT FROM AUTHOR]

Abstract: Objective: Prompt ascertainment is crucial for the management of hyperammonemic infants. Because these patients are rare and recognition of hyperammonemia is often delayed, we designed and implemented an electronic medical record (EMR)-based tool to assist physicians in the detection of hyperammonemia. Methods: We retrospectively evaluated the hospitalizations of prior hyperammonemic infants to identify codable elements that could trigger an EMR-based warning. An alert was designed and implemented and its utilization was prospectively analyzed. Results: Blood gas studies were obtained universally and early in the retrospectively evaluated infants ( =26h before ammonia level). Prompting physicians to evaluate ammonia after ordering blood gas studies would have accelerated the initial ammonia order in 89% of retrospective cases. The alert has activated 184 times over the first six months of operation leading to 63 laboratory evaluations and detection of one hyperammonemic infant. Conclusion: Implementation of an EMR-based warning system can improve surveillance for hyperammonemia in a susceptible population. [Copyright &y& Elsevier]

Urea cycle disorders (UCD) are common during neonatal period, and it is rarely reported in adults. We are reporting a patient presenting with post-partum neuropsychiatric symptoms rapidly progressing to coma. Markedly raised serum ammonia level on presentation with an initial normal magnetic resonance imaging (MRI) of brain and normal liver function tests led to the suspicion of UCD, which was confirmed on the basis of urine orotic acid and elevated serum amino acid levels. We had to resort to hemodialysis to correct the hyperammonemic coma, which was unresponsive to conventional anti-ammonia measures. She exhibited remarkable improvement with a progressive decline in serum ammonia with repeated hemodialysis and made a full recovery. Timely diagnosis and early institution of hemodialysis in the setting of a poor neurological status maybe considered a suitable treatment option. [ABSTRACT FROM AUTHOR]

Background & Aims: Hyperammonemia results from reduction of hepatocyte function or enzyme of urea cycle deficiency. Hyperammonemia contributes to cerebral edema that may lead to cerebral herniation. The threshold of toxicity of ammonemia is unknown. Methods: We conducted a retrospective observational study in our pediatric intensive care unit. All children who developed hyperammonemia from January 2000 to April 2009 were included. Clinical and laboratory data at admission, specific treatments implemented, and ammonemias the first 7days after inclusion were collected. The outcome assessed was 28day mortality. Risk of mortality was estimated by a logistic regression model. Results: Ninety patients with liver failure (63.3%) and primary or secondary urea cycle defect (23.3%) were included. Patients with urea cycle defects were more likely to receive ammonia scavengers than patients with liver failure (47.6% versus 3.5%). The 28day mortality rate was 31.1%. Risk of mortality increased according to the ammonemia within 48h: odds ratio 1.5, 1.9, 3.3, 2.4 for ammonemia above 100, 150, 200, and 300μmol/L, respectively. Peak ammonemia ⩾200μmol/L within the first 48h was an independent risk factor for mortality, with greater risk found in liver failure than in urea cycle defect. Conclusions: Our study identifies a threshold of exposure to ammonia (⩾200μmol/L) above which mortality increases significantly, especially in liver failure. Specific treatments of hyperammonemia are rarely used in liver failure when compared with urea cycle defect even though use of ammonia scavengers may help to decrease ammonemia. [ABSTRACT FROM AUTHOR]

Abstract: Citrin is the liver-specific isoform of the mitochondrial aspartate/glutamate carrier (AGC2). AGC2 deficiency is an autosomal recessive disorder with two age related phenotypes: neonatal intrahepatic cholestasis (NICCD, OMIM#605814) and adult-onset type II citrullinemia (CTLN2, OMIM#603471). NICCD arises within the first few weeks of life resulting in prolonged cholestasis and metabolic abnormalities including aminoacidemia and galactosuria. Usually symptoms disappear within the first year of life, thus making a diagnosis difficult after this time. In this study we report a new Caucasian case of NICCD, a seven week old Romanian boy with prolonged jaundice. Sequencing of the AGC2 gene showed a novel homozygous missense double-nucleotide (doublet) mutation, which produces the change of the glycine at position 437 into glutamate. Functional studies, carried out on the recombinant mutant protein, for the first time demonstrated, that NICCD is caused by a reduced transport activity of AGC2. The presence of AGC2 deficiency in other ethnic groups besides Asian population suggests further consideration for NICCD diagnosis of any neonate with an unexplained cholestasis; a prompt diagnosis is crucial to resolve the metabolic decompensation with an appropriate dietary treatment. [Copyright &y& Elsevier]

Abstract: Citrullinemia type I (CTLN1) is a urea cycle disorder which typically presents in the neonatal period or infancy with hyperammonemia and concurrent neurologic deterioration. We report a 15-month-old female with CTLN1 who presented with encephalopathy and seizures with hyperammonemia requiring emergency treatment. Although there was a rapid resolution of her hyperammonemia, she developed fulminant liver failure. The severe increase of transaminases (aspartate aminotransferase and alanine aminotransferase levels peaking at 19,794UI/L and 19,938UI/L, respectively) and concurrent disturbances in her hepatic synthetic functions led to the consideration of a liver transplantation. However, there was a normalization of her liver function tests over the course of weeks with supportive therapy alone. Molecular analysis of the ASS1 gene confirmed the diagnosis of CTLN1 by revealing the known mutation c.1087C>T (p.R363W) on the paternal allele and an intronic nucleotide exchange leading to an insertion of 69bp on the transcript resulting in a frameshift and premature stop of translation on the maternal allele. We also briefly report another case of CTLN1 where liver failure was a prominent feature of the presentation. Fulminant liver failure has been described with a variety of other urea cycle disorders, but has been described in infantile onset presentation of CTLN1 in only two other cases recently. Our observation suggests that in some cases of CTLN1 with acute liver failure, emergency intervention such as transplantation is not warranted despite evidence of severe hepatotoxicity. [Copyright &y& Elsevier]

Ornithine transcarbamylase (OTC) deficiency is the most frequent innate disorder of the urea cycle and is X-chromosome linked. The disease normally manifests itself shortly after birth and is fatal when untreated. Due to the different expression and X-chromosomal inheritance the manifestation of symptoms can appear later particularly in girls and young women. The first symptoms are non-specific signs of elevated cerebral pressure as a result of a hyperammonemia, which range from nausea and headache up to cerebral herniation with fatal outcome. Measurement of plasma ammonia levels is a simple yet important screening test for patients with unexpected stupor or delirium. The two case reports show the clinical range from acute decompensation with acute cerebral herniation followed by fatal outcome to recovery under emergency therapy without substantial neurological deficits. Emergency treatment consists of symptomatic securing of vital parameters and an immediate reduction in the ammonia level using high calorie, protein-free nutrition to avoid catabolism together with administration of arginine, benzoate or phenyl butyrate. In cases of coma with severe cerebral edema and the threat of a herniation reaction or excessive ammonia levels, emergency hemodialysis must be immediately carried out. In the clinical routine it is extremely important to consider a metabolic defect at an early phase and among others to determine the ammonia level so that the appropriate treatment can be instigated in time. [ABSTRACT FROM AUTHOR]

Abstract: Background: Ornithine transcarbamylase (OTC) deficiency is the most common inborn error of urea metabolism that can lead to hyperammonemic crises and orotic aciduria. To date, a total of 341 causative mutations within the OTC gene have been described. However, in about 20% of the patients with enzymatically confirmed OTC deficiency no mutation can be detected when sequencing of genomic DNA analyzing exons and adjacent intronic segments of the OTC gene is performed. Methods: Standard genomic DNA analysis of the OTC gene in five consecutive patients from five families revealed no mutation. Hence, liver tissue was obtained by needle sampling or open biopsy and RNA extracted from liver was analyzed. Results: Complex rearrangements of the OTC transcript (three insertions and two deletions) were found in all five patients. Conclusion: In patients with a strong suspicion of OTC deficiency despite normal results of sequencing exonic regions of the OTC gene, characterization of liver OTC mRNA is highly effective in resolving the genotype. Liver tissue sampling by needle aspiration allows for both enzymatic analysis and RNA based diagnostics of OTC deficiency. [Copyright &y& Elsevier]

Background. Hyperammonemia caused by ornithine transcarbamylase (OTC) deficiency can be properly managed by continuous arteriovenous hemodiafiltration (CAVHDF). Removal of amino acids (AA) during CAVHDF has not been thoroughly investigated. AA losses in patients with urea cycle defects due to ornithine transcarbamylase deficiency treated by CAVHDF were analyzed. Methods. Twelve neonates with elevated serum ammonia levels, confirmed through urine organic acid analysis and serum amino acid studies, were documented to have OTC deficiency. CAVHDF was administered in an attempt to lower serum ammonia concentration. Amino acid analysis of ultrafiltration and serum were performed by liquid chromatography. Results. Serum levels of leucine, isoleucine, methionine, phenylalanine, and tyrosine were significantly lower than acceptable in these patients. Glutamine was the only amino acid that increased significantly, which is clinically relevant to OTC enzyme deficiency. Although the mean serum concentrations of tyrosine and glutamine concentrations were lower in the dialysate, the serum and dialysate concentrations of other amino acids did not differ. Conclusion. CAVHDF may induce changes in amino acid metabolism and distribution as well. The requirement of aminogram monitor for amino acid supplementation in urea cycle defect patients is important. [ABSTRACT FROM AUTHOR]

Urea cycle defects (UCDs) typically present with hyperammonemia, the duration and peak levels of which are directly related to the neurologic outcome. Liver transplantation can cure the underlying defect for some conditions, but the preexisting neurologic status is a major factor in the final outcome. Multicenter data indicate that most of the children who receive transplants remain significantly neurologically impaired. We wanted to determine whether aggressive metabolic management of ammonia levels after early referral/transfer to a metabolism center and early liver transplantation would result in better neurologic outcomes. We report on 5 children with UCDs, ie, 2 male patients with X-linked ornithine transcarbamylase deficiency and 2 male patients with carbamoyl phosphate synthase deficiency, all of whom had neonatal presentations and underwent orthotopic liver transplantation before 1 year of age, and 1 female patient with partial X-linked ornithine transcarbamylase deficiency that was intractable to medical therapy, who underwent transplantation at 35 months of age. Developmental testing with the Griffiths scale was performed on 3 occasions each, 12 months apart, up to 45 months after transplantation. Full-scale indices for 3 children who underwent early transplantation showed average developmental quotients of 67. All 5 children had metabolic cures. There were no deaths (30-month survival rate: 100%). One child is currently listed for repeat transplantation because of bile duct stenosis and cirrhosis. We conclude that early liver transplantation and aggressive metabolic management improve early neurologic outcomes for children with UCDs, but longer follow-up monitoring is needed. [ABSTRACT FROM AUTHOR]

The clinical syndrome of encephalopathy is most often encountered in the context of decompensated liver disease and the diagnosis is usually clear cut. Non-hepatic causes of encephalopathy are rarer and tend to present to a wide range of medical specialties with variable and episodic symptoms. Delay can result in the development of potentially life threatening complications, such as seizures and coma. Early recognition is vital. A history of similar episodes or clinical risk factors and early assessment of blood ammonia levels help establish the diagnosis. In addition to adequate supportive care, investigation of the underlying cause of the hyperammonaemia is essential and its reversal, where possible, will often result in complete recovery. Detection of an unborn error of metabolism should lead to the initiation of appropriate maintenance therapy and genetic counselling. [ABSTRACT FROM AUTHOR]

Urea cycle disorders (UCDs) are a group of rare inherited metabolic diseases causing hyperammonemic encephalopathy. Despite intensive dietary and pharmacological therapy, outcome is poor in a subset of UCD patients. Reducing ammonia production by changing faecal microbiome in UCD is an attractive treatment approach. We compared faecal microbiome composition of 10 UCD patients, 10 healthy control subjects and 10 phenylketonuria (PKU) patients. PKU patients on a low protein diet were included to differentiate between the effect of a low protein diet and the UCD itself on microbial composition. Participants were asked to collect a faecal sample and to fill out a 24 h dietary journal. DNA was extracted from faecal material, taxonomy was assigned and microbiome data was analyzed, with a focus on microbiota involved in ammonia metabolism.In this study we show an altered faecal microbiome in UCD patients, different from both PKU and healthy controls. UCD patients on dietary and pharmacological treatment had a less diverse faecal microbiome, and the faecal microbiome of PKU patients on a protein restricted diet with amino acid supplementation showed reduced richness compared to healthy adults without a specific diet. The differences in the microbiome composition of UCD patients compared to healthy controls were in part related to lactulose use. Other genomic process encodings involved in ammonia metabolism, did not seem to differ. Since manipulation of the microbiome is possible, this could be a potential treatment modality. We propose as a first next step, to study the impact of these faecal microbiome alterations on metabolic stability., Take Home Message: The faecal microbiome of UCD patients was less diverse compared to PKU patients and even more compared to healthy controls., Competing Interests: CT, MD, JHML, JGL, MB and NAM declare to have no conflict of interest. ML is involved in premarketing studies with Genzyme, Protalix and Idorsia. MN is in the Scientific Advisory Board of Caelus Pharmaceuticals, the Netherlands and Kaleido, USA. None of these are directly relevant to the current paper., (© 2021 The Authors.)

The urea cycle generates arginine that is one of the major precursors for creatine biosynthesis. Here we evaluate levels of creatine and guanidinoacetate (the precursor in the synthesis of creatine) in plasma samples (n s  = 207) of patients (n p  = 73) with different types of urea cycle disorders (ornithine transcarbamylase deficiency (n s  = 22; n p  = 7), citrullinemia type 1 (n s  = 60; n p  = 22), argininosuccinic aciduria (n s  = 81; n p  = 31), arginase deficiency (n s  = 44; n p  = 13)). The concentration of plasma guanidinoacetate positively correlated ( p  < 0.001, R 2  = 0.64) with levels of arginine, but not with glycine in all patients with urea cycle defects, rising to levels above normal in most samples (34 out of 44) of patients with arginase deficiency. In contrast to patients with guanidinoacetate methyltransferase deficiency (a disorder of creatine synthesis characterized by elevated guanidinoacetate concentrations), creatine levels were normal (32 out of 44) or above normal (12 out of 44) in samples from patients with arginase deficiency. Creatine levels correlated significantly, but poorly ( p  < 0.01, R 2  = 0.1) with guanidinoacetate levels and, despite being overall in the normal range in patients with all other urea cycle disorders, were occasionally below normal in some patients with argininosuccinic acid synthase and lyase deficiency. Creatine levels positively correlated with levels of methionine ( p  < 0.001, R 2  = 0.16), the donor of the methyl group for creatine synthesis. The direct correlation of arginine levels with guanidinoacetate in patients with urea cycle disorders explains the increased concentration of guanidino compounds in arginase deficiency. Low creatine levels in some patients with other urea cycle defects might be explained by low protein intake (creatine is naturally present in meat) and relative or absolute intracellular arginine deficiency., Competing Interests: All authors state that they have no competing interests to declare. None of the authors accepted any reimbursements, fees or funds from any organization that may in any way gain or lose financially from the results of this study., (© 2021 The Authors.)

Three steps are extremely important in emergency management (awaiting diagnosis) of organic acidurias and urea cycle disorders. The first is to obtain adequate samples (blood and urine) before any treatment, parenteral and/or enteral nutrition with protein-free solution and toxin removal procedures are the second step. Additional therapies with cofactors and vitamins are the last step. It is very important carry out quickly this strategy every time we suspect an inborn error of metabolism. [ABSTRACT FROM AUTHOR]

A 7-year-old female patient with a new diagnosis of ornithine transcarbamylase deficiency was treated for hyperammonemia with a standard protocol. Several days later, she developed ataxia, dysmetria, and dysarthria. Magnetic resonance imaging of the brain demonstrated pontine and extrapontine white matter changes consistent with osmotic demyelination. Classically described as a consequence of hyponatremia treatment, osmotic demyelination syndrome has rarely been associated with other entities. This case suggests a potentially serious complication of the standard therapy for hyperammonemia in patients with ornithine transcarbamylase deficiency. [ABSTRACT FROM AUTHOR]

Abstract: MR spectroscopy in a patient with argininosuccinate lyase deficiency revealed elevated cerebral guanidinoacetate signals, indicating that the phenomenon of increased levels of this compound in brain tissue is not limited to creatine deficiencies. [Copyright &y& Elsevier]

N -acetyl glutamate synthase (NAGS) deficiency is the rarest urea cycle defect presenting as neonatal onset life-threatening hyperammonemia. We report here a family history of severe NAGS deficiency: after the index-case with severe hyperammonemia, one patient benefited from antenatal diagnosis, and from primary care at birth, another one was diagnosed at 2-days and immediately treated with carbaglumic-acid. Finally, we report excellent tolerance to long-term carbaglumic-acid treatment, with no side effects, and healthy neurological and psychomotor development., (© 2019 The Authors.)