Argininosuccinic Aciduria Research Articles

Maternal uniparental disomy of chromosome 7 underlying argininosuccinic aciduria and Silver-Russell syndrome

We describe a patient presenting with argininosuccinic aciduria and Silver-Russell syndrome (SRS). SRS was caused by maternal uniparental disomy of chromosome 7 (UPD(7)mat). UPD(7)mat also unmasked a maternally inherited splicing variant in ASL on chromosome 7, leading to the onset of argininosuccinic aciduria. The phenotype of the present case was more severe than that of a previous case, demonstrating a phenotypic variation in the combination of argininosuccinic aciduria and SRS.

Clinical Characteristics of Pediatric Patients with Urea Cycle Disorders

Objective: Urea cycle disorders (UCDs) are inherited deficiencies of the enzymes or transport molecules involved in the cellular excretion of excess ammonia produced during protein metabolism. The aim of this study was to evaluate the clinical characteristics and long-term outcome of pediatric patients with UCDs. Material and Methods: Our research was conducted between September 2020-March 2021 in Dr. Sami Ulus Maternity and Child Health Training and Research Hospital. Clinical characteristics in 16 patients with UCDs [carbamoyl phosphate synthetase I deficiency (n=1), N-acetylglutamate synthase deficiency(n=1), argininosuccinate lyase deficiency (n=4), argininosuccinate synthetase deficiency (n=4), arginase deficiency (n=2), ornithine transcarbamylase deficiency (n=2), hyperammonemia hyperornithinemia homocitrullinuria syndrome (n=2)] were defined. The term “neonatal-onset” UCD was used if symptoms occurred within 28 days of life, and “late-onset” if symptoms started after the neonatal period. Results: Eight patients presented with acute metabolic crisis during newborn period. Core clinical phenotype in neonatal-onset UCDs included sepsis-like findings, whereas epilepsy and mental retardation was predominant in lateonset UCDs. For patients with neonatal-onset UCDs, hyperammonemia was more severe at the initial period. Conclusion: Despite evolving treatment opportunities, still high mortality rates were found in neonatal-onset UCD. UCDs should be suspected in pediatric patients with hyperammonemia and metabolic investigations should be performed immediately to enlighten diagnosis. Neonatal-onset UCD usually present with symptoms of acute hyperammonemia, while moresubtle neurological manifestations are frequent initial findings in the late onset UCD.

Characterisation of Expression the Arginine Pathway Enzymes in Childhood Brain Tumours to Determine Susceptibility to Therapeutic Arginine Depletion.

Despite significant improvements in treatment and survival in paediatric cancers, outcomes for children with brain tumours remain poor. Novel therapeutic approaches are needed to improve survival and quality of survival. Extracellular arginine dependency (auxotrophy) has been recognised in several tumours as a potential therapeutic target. This dependency is due to the inability of cancer cells to recycle or synthesise intracellular arginine through the urea cycle pathway compared to normal cells. Whilst adult glioblastoma exhibits this dependency, the expression of the arginine pathway enzymes has not been delineated in paediatric brain tumours. We used immunohistochemical (IHC) methods to stain for arginine pathway enzymes in paediatric high-grade glioma (pHGG), low-grade glioma (pLGG), ependymoma (EPN), and medulloblastoma (MB) tumour tissue microarrays (TMAs). The antibodies detected protein expression of the metaboliser arginase (Arg1 and Arg2); recycling enzymes ornithine transcarbamoylase (OTC), argininosuccinate synthetase (ASS1), and argininosuccinate lyase (ASL); and the transporter SLC7A1. Deficiency of OTC, ASS1, and ASL was seen in 87.5%, 94%, and 79% of pHGG samples, respectively, consistent with an auxotrophic signature. Similar result was obtained in pLGG with 96%, 93%, and 91% of tumours being deficient in ASL, ASS1, and OTC, respectively. 79%, 88%, and 85% of MB cases were ASL, ASS1, and OTC deficient whilst ASL and OTC were deficient in 57% and 91% of EPN samples. All tumour types highly expressed SLC7A1 and Arginase, with Arg2 being the main isoform, demonstrating that they could transport and utilise arginine. Our results show that pHGG, pLGG, EPN, and MB demonstrate arginine auxotrophy based on protein expression and are likely to be susceptible to arginine depletion. Pegylated arginase (BCT-100) is currently in phase I/II trials in relapsed pHGG. Our results suggest that therapeutic arginine depletion may also be useful in other tumour types and IHC analysis of patient tumour samples could help identify patients likely to benefit from this treatment.

Unmet Needs of Parents of Children with Urea Cycle Disorders.

(1) Background: Phenotypic diversity and long-term health outcomes of individuals with urea cycle disorders (UCDs) have been described in detail. However, there is limited information on the burden on affected families. (2) Methods: To evaluate the family burden in parents with children suffering from UCDs, we used validated questionnaires. Socio-demographic characteristics were evaluated, and an adapted version of the Parental Need Scale for Rare Diseases questionnaire was used. The survey was conducted in families of UCD patients cared for at the University Children’s Hospital Heidelberg. (3) Results: From April to November 2021, 59 participants were interviewed (mothers n = 34, fathers n = 25). The affected patients most frequently suffered from ornithine transcarbamylase deficiency (OTC-D) (female n = 12, male n = 12), followed by argininosuccinate synthetase deficiency (ASS-D, n = 13) and argininosuccinate lyase deficiency (ASL-D, n = 8). About one-third of the participants were “dissatisfied” or “extremely dissatisfied” with health professionals’ disease knowledge. In addition, 30% of the participants reported a medium or high need for “additional information on the development of their children”, and 44% reported a medium or high need “for information on available services”. A majority of 68% reported a need for additional support regarding services such as support groups (42%) or psychological counseling (29%). (4) Conclusions: Our study indicates that there is an unmet need for sufficient information about the development of children with UCDs, as well as for information about available support services for families with UCD patients. Furthermore, the results highlight the importance of establishing or improving family-centered care approaches. This pilot study may serve as a template for the assessment of the family burden associated with other inherited metabolic diseases.

Clinical diagnosis of metabolic disorders using untargeted metabolomic profiling and disease-specific networks learned from profiling data

Untargeted metabolomics is a global molecular profiling technology that can be used to screen for inborn errors of metabolism (IEMs). Metabolite perturbations are evaluated based on current knowledge of specific metabolic pathway deficiencies, a manual diagnostic process that is qualitative, has limited scalability, and is not equipped to learn from accumulating clinical data. Our purpose was to improve upon manual diagnosis of IEMs in the clinic by developing novel computational methods for analyzing untargeted metabolomics data. We employed CTD, an automated computational diagnostic method that “connects the dots” between metabolite perturbations observed in individual metabolomics profiling data and modules identified in disease­specific metabolite co-perturbation networks learned from prior profiling data. We also extended CTD to calculate distances between any two individuals (CTDncd) and between an individual and a disease state (CTDdm), to provide additional network-quantified predictors for use in diagnosis. We show that across 539 plasma samples, CTD-based network-quantified measures can reproduce accurate diagnosis of 16 different IEMs, including adenylosuccinase deficiency, argininemia, argininosuccinic aciduria, aromatic l-amino acid decarboxylase deficiency, cerebral creatine deficiency syndrome type 2, citrullinemia, cobalamin biosynthesis defect, GABA-transaminase deficiency, glutaric acidemia type 1, maple syrup urine disease, methylmalonic aciduria, ornithine transcarbamylase deficiency, phenylketonuria, propionic acidemia, rhizomelic chondrodysplasia punctata, and the Zellweger spectrum disorders. Our approach can be used to supplement information from biochemical pathways and has the potential to significantly enhance the interpretation of variants of uncertain significance uncovered by exome sequencing. CTD, CTDdm, and CTDncd can serve as an essential toolset for biological interpretation of untargeted metabolomics data that overcomes limitations associated with manual diagnosis to assist diagnosticians in clinical decision-making. By automating and quantifying the interpretation of perturbation patterns, CTD can improve the speed and confidence by which clinical laboratory directors make diagnostic and treatment decisions, while automatically improving performance with new case data.

The diagnostic challenge of mild citrulline elevation at newborn screening.

Citrulline is a target analyte measured at expanded newborn screening (NBS) and its elevation represents a biomarker for distal urea cycle disorders and citrin deficiency. Altered ratios of citrulline with other urea cycle-related amino acids are helpful for the differential diagnosis. However, the use of cut-off values in screening programmes has raised the issue about the interpretation of mild elevation of citrulline levels detected at NBS, below the usual range observed in the "classical/severe" forms of distal urea cycle disorders and in citrin deficiency. Herein, we report ten subjects with positive NBS for a mild elevation of citrulline (<100 μmol/L), in whom molecular investigations revealed carriers status for argininosuccinate synthase deficiency, a milder form of argininosuccinate lyase deficiency and two other diseases, lysinuric protein intolerance and dihydrolipoamide dehydrogenase deficiency, not primarily affecting the urea cycle. To guide the diagnostic process, we have designed an algorithm for mild citrulline elevation (<100 μmol/L) at NBS, which expands the list of disorders to be included in the differential diagnosis.

Inborn error of metabolism patients after liver transplantation: Outcomes of 35 patients over 27 years in one pediatric quaternary hospital.

Liver transplantation (LT) has been used for many years as a therapeutic option for certain inborn errors of metabolism (IEMs). Here we present one institution's 27 years of experience with LT in IEMs. Our objective is to assess the outcomes of IEM patients who have undergone LT, which we hypothesize to be generally successful for prevention of metabolic decompensation. A retrospective chart review was performed on patients with urea cycle defects, organic acidemias, and amino acidopathies who underwent LT at the Children's Hospital of Philadelphia. Thirty-five patients with the following conditions have undergone LT: tyrosinemia (8), methylmalonic acidemia (7), maple syrup urine disease (6), citrullinemia (6), ornithine transcarbamylase deficiency (4), propionic acidemia (2), and argininosuccinate lyase deficiency (2). Average age at transplantation was 3.6 years. Three patients are now deceased. One patient suffered a metabolic stroke posttransplant. No episodes of metabolic decompensation have been noted. Thirty-five patients received LT with generally favorable outcome. None sustained metabolic decompensation posttransplant. As has been reported previously, LT does not ameliorate pre-existing developmental differences or risk to other organ systems. Further research is needed to aid in standardization of care and follow-up, as most patients no longer follow with a geneticist.

Hepatic Manifestations of Urea Cycle Disorders.

Content available: Author Interview and Audio Recording.

Creatine metabolism in patients with urea cycle disorders

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 < 0.001, R2 = 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, R2 = 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, R2 = 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.

Liver Transplantation in Children with Urea Cycle Disorders: The Importance of Minimizing Waiting Time.

Liver transplantation (LT) for children with urea cycle disorders (UCDs) is capable of correcting the enzymatic defect and preventing progressive neurologic injury. We describe the characteristics and outcomes of pediatric LT recipients with UCDs. We identified all pediatric (<18 years) LT candidates with UCDs in the United Network for Organ Sharing (UNOS) database (February 2002 to September 2020). Multivariable Cox and logistic regression were used to determine risk factors for graft loss and cognitive delay, respectively. Of 424 patients, 1.9% (8/424) experienced waitlist mortality and 95.0% underwent LT (403/424). The most frequently encountered UCDs in our cohort were ornithine transcarbamylase deficiency (46.2%), citrullinemia (20.3%), and argininosuccinic aciduria (ASA; 12.9%). The 1‐, 3‐, and 5‐year graft survival rates were 90.4%, 86.3%, and 85.2%, respectively. Multivariable analysis showed a decreased risk of graft loss with increasing weight at LT (adjusted hazard ratio [aHR], 0.96; 95% confidence interval [CI], 0.94‐0.99; P = 0.02), male sex (aHR, 0.49; 95% CI, 0.28‐0.85; P = 0.01), and ASA diagnosis (aHR, 0.29; 95% CI, 0.09‐0.98; P = 0.047), when adjusting for location (intensive care/hospital/home) and graft type (both P ≥ 0.65). In multivariable logistic regression, waitlist time (adjusted odds ratio [aOR], 1.10; 95% CI, 1.02‐1.17; P = 0.009) and male sex (aOR, 1.71; 95% CI, 1.02‐2.88; P = 0.04) were associated with increased odds of long‐term cognitive delay. Waitlist duration is associated with a long‐term risk of cognitive delay. Given excellent long‐term outcomes, early LT evaluation should be considered in all children with UCDs to prevent progressive neurologic injury and optimize cognitive outcomes.

Adult-onset diagnosis of urea cycle disorders: Results of a French cohort of 71 patients.

Urea cycle disorders (UCD) are rare diseases that usually affect neonates or young children. During decompensations, hyperammonemia is neurotoxic, leading to severe symptoms and even coma and death if not treated rapidly. The aim was to describe a cohort of patients with adult onset of UCDs in a multicentric, retrospective and descriptive study of French adult patients with a diagnosis after 16 years of age of UCDs due to a deficiency in one of the 6 enzymes (arginase, ASL, ASS, CPS1, NAGS, OTC) or the two transporters (ORNT1 or citrin). Seventy-one patients were included (68% female, 32% male). The diagnosis was made in the context of (a) a metabolic decompensation (42%), (b) family history (55%), or (c) chronic symptoms (3%). The median age at diagnosis was 33 years (range 16-86). Eighty-nine percent of patients were diagnosed with OTC deficiency, 7% CPS1 deficiency, 3% HHH syndrome and 1% argininosuccinic aciduria. For those diagnosed during decompensations (including 23 OTC cases, mostly female), 89% required an admission in intensive care units. Seven deaths were attributed to UCD-6 decompensations and 1 epilepsy secondary to inaugural decompensation. This is the largest cohort of UCDs diagnosed in adulthood, which confirms the triad of neurological, gastrointestinal and psychiatric symptoms during hyperammonemic decompensations. We stress that females with OTC deficiency can be symptomatic. With 10% of deaths in this cohort, UCDs in adults remain a life-threatening condition. Physicians working in adult care must be aware of late-onset presentations given the implications for patients and their families.

Long‐term outcome of urea cycle disorders: Report from a nationwide study in Japan

Urea cycle disorders (UCDs) are inherited metabolic disorders with impaired nitrogen detoxification caused by defects in urea cycle enzymes. They often manifest with hyperammonemic attacks resulting in significant morbidity or death. We performed a nationwide questionnaire-based study between January 2000 and March 2018 to document all UCDs in Japan, including diagnoses, treatments, and outcomes. A total of 229 patients with UCDs were enrolled in this study: 73 males and 53 females with ornithine transcarbamylase deficiency (OTCD), 33 patients with carbamoylphosphate synthetase 1 deficiency, 48 with argininosuccinate synthetase deficiency, 14 with argininosuccinate lyase deficiency, and 8 with arginase deficiency. Survival rates at 20 years of age of male and female patients with late-onset OTCD were 100% and 97.7%, respectively. Blood ammonia levels and time of onset had a significant impact on the neurodevelopmental outcome (P < .001 and P = .028, respectively). Hemodialysis and liver transplantation did not prevent poor neurodevelopmental outcomes. While treatment including medication, hemodialysis, and liver transplantation may aid in decreasing blood ammonia and/or preventing severe hyperammonemia, a blood ammonia level ≥ 360 μmol/L was found to be a significant indicator for a poor neurodevelopmental outcome. In conclusion, although current therapy for UCDs has advanced and helped saving lives, patients with blood ammonia levels ≥ 360 μmol/L at onset often have impaired neurodevelopmental outcomes. Novel neuroprotective measures should therefore be developed to achieve better neurodevelopmental outcomes in these patients.

Variants associated with urea cycle disorders in Japanese patients: Nationwide study and literature review.

Urea cycle disorders (UCDs) are inherited metabolic diseases that lead to hyperammonemia with variable clinical manifestations. Using data from a nationwide study, we investigated the onset time, gene variants, clinical manifestations, and treatment of patients with UCDs in Japan. Of the 229 patients with UCDs diagnosed and/or treated between January 2000 and March 2018, identified gene variants and clinical information were available for 102 patients, including 62 patients with ornithine transcarbamylase (OTC) deficiency, 18 patients with carbamoyl phosphate synthetase 1 (CPS1) deficiency, 16 patients with argininosuccinate synthetase (ASS) deficiency, and 6 patients with argininosuccinate lyase (ASL) deficiency. A total of 13, 10, 4, and 5 variants in the OTC, CPS1, ASS, and ASL genes were respectively identified as novel variants, which were neither registered in ClinVar databases nor previously reported. The onset time and severity in patients with UCD could be predicted based on the identified gene variants in each patient from this nationwide study and previous studies. This genetic information may help in predicting the long-term outcome and determining specific treatment strategies such as liver transplantation in patients with UCDs.

Physical, cognitive, and social status of patients with urea cycle disorders in Japan

Urea cycle disorders (UCDs) are inherited metabolic diseases that lead to hyperammonemia. Severe hyperammonemia adversely affects the brain. Therefore, we conducted a nationwide study between January 2000 and March 2018 to understand the present status of UCD patients in Japan regarding diagnosis, treatments, and outcomes. A total of 229 patients with UCDs (126 patients: ornithine transcarbamylase deficiency [OTCD]; 33: carbamoyl phosphate synthetase 1 deficiency [CPS1D]; 48: argininosuccinate synthetase deficiency [ASSD]; 14: argininosuccinate lyase deficiency [ASLD]; and 8: arginase 1 deficiency [ARG1D]) were enrolled in the present study. Although growth impairment is common in patients with UCDs, we discovered that Japanese patients with UCDs were only slightly shorter than the mean height of the general adult population in Japan. Patients with neonatal-onset UCDs are more likely to experience difficulty finding employment and a spouse; however, some patients with late-onset UCDs were employed and married. Additionally, intellectual and developmental disabilities, such as attention deficit hyperactivity disorder (ADHD) and autism, hinder patients with UCDs from achieving a healthy social life. Moreover, we identified that it is vital for patients with UCDs presenting with mild to moderate intellectual disabilities to receive social support. Therefore, we believe the more robust social support system for patients with UCDs may enable them to actively participate in society.

Beclin‐1‐mediated activation of autophagy improves proximal and distal urea cycle disorders

Urea cycle disorders (UCD) are inherited defects in clearance of waste nitrogen with high morbidity and mortality. Novel and more effective therapies for UCD are needed. Studies in mice with constitutive activation of autophagy unravelled Beclin‐1 as druggable candidate for therapy of hyperammonemia. Next, we investigated efficacy of cell‐penetrating autophagy‐inducing Tat‐Beclin‐1 (TB‐1) peptide for therapy of the two most common UCD, namely ornithine transcarbamylase (OTC) and argininosuccinate lyase (ASL) deficiencies. TB‐1 reduced urinary orotic acid and improved survival under protein‐rich diet in spf‐ash mice, a model of OTC deficiency (proximal UCD). In AslNeo/Neo mice, a model of ASL deficiency (distal UCD), TB‐1 increased ureagenesis, reduced argininosuccinate, and improved survival. Moreover, it alleviated hepatocellular injury and decreased both cytoplasmic and nuclear glycogen accumulation in AslNeo/Neo mice. In conclusion, Beclin‐1‐dependent activation of autophagy improved biochemical and clinical phenotypes of proximal and distal defects of the urea cycle.

Severity-adjusted evaluation of newborn screening on the metabolic disease course in individuals with cytosolic urea cycle disorders

ObjectiveThe implementation of newborn screening (NBS) programs for citrullinemia type 1 (CTLN1) and argininosuccinic aciduria (ASA) is subject to controversial debate. The aim of this study was to assess the impact of NBS on the metabolic disease course and clinical outcome of affected individuals. MethodsIn 115 individuals with CTLN1 and ASA, we compared the severity of the initial hyperammonemic episode (HAE) and the frequency of (subsequent) HAEs with the mode of diagnosis. Based on a recently established functional disease prediction model, individuals were stratified according to their predicted severe or attenuated phenotype. ResultsIndividuals with predicted attenuated forms of CTLN1 and ASA were overrepresented in the NBS group, while those with a predicted severe phenotype were underrepresented compared to individuals identified after the manifestation of symptoms (SX). Identification by NBS was associated with reduced severity of the initial HAE both in individuals with predicted severe and attenuated phenotypes, while it was not associated with lower frequency of (subsequent) HAEs. Similar results were obtained when including some patients diagnosed presymptomatically (i.e. prenatal testing, and high-risk family screening) in this analysis. ConclusionSince one of the major challenges of NBS outcome studies is the potential overrepresentation of individuals with predicted attenuated phenotypes in NBS cohorts, severity-adjusted evaluation of screened and unscreened individuals is important to avoid overestimation of the NBS effect. NBS enables the attenuation of the initial HAE but does not affect the frequency of subsequent metabolic decompensations in individuals with CTLN1 and ASA. Future long-term studies will need to evaluate the clinical impact of this finding, especially with regard to mortality, as well as cognitive outcome and quality of life of survivors.

Determination of amino acid profile for argininosuccinic aciduria disorder using High-Performance Liquid Chromatography with fluorescence detection.

Argininosuccinic aciduria is an autosomal, recessive amino acid disorder that is caused by a deficiency of the argininosuccinate lyase enzyme. Citrulline is the most significant marker to detect this disorder. We used the High-performance liquid chromatography with fluorescence detection with 450 nm emission and 330 nm excitation wavelengths, 15 mmol/L potassium dihydrogen phosphate and 5 mmol/L dipotassium hydrogen phosphate as Mobile Phase A, and 50 mL water, 250 mL acetonitrile, and 200 mL methanol as Mobile Phase B in gradient mode with flow rate of 1.2 mL/min. The citrulline concentration was 22 µmol/L in healthy infants and 220 µmol/L in infants suffering from the disorder.

Urea Cycle Disorders: A Neuroimaging Pattern Approach Using Diffusion and FLAIR MRI.

This study aimed to assess characteristic regions of MRI involvement utilizing diffusion weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) at urea cycle disorder (UCD) diagnosis to determine the possible association between initial MRI patterns within 10days of the first hyperammonemia episode, serum ammonia levels, and severity of neurological outcome based on clinical follow-up of >30 days. Ten patients with UCDs (4 females; median age: 5.4 years, age range: 6 days-54 years) were included who underwent MRI during a first episode of hyperammonemia. The topographical distribution of the DWI and FLAIR abnormalities in the cerebral cortex, deep gray matter, white matter, posterior limb of internal capsule, cerebral peduncle, and cerebellum was evaluated. Possible correlations between the brain injury patterns on DWI/FLAIR images, serum ammonia levels, and severity of neurological outcome were investigated by a trend correlation. The UCD cohort (n = 10) involved four ornithine transcarbamoylase deficiencies, four argininosuccinic aciduria, one carbomoylphosphate synthetase deficiency, and one citrullinemia type-1. The observed trend in the distribution of DWI abnormalities as the severity of neurological sequela outcome increased was with diffuse cerebral cortex or corpus striatum involvement. Patients with initial peak serum ammonia ≥450 µmol/L had a grade 2 to 4 outcome, and those with peak ammonia <450 µmol/L had a grade 0 or 1 outcome. The presence of more severe neurological outcome could be associated with diffuse cerebral cortex or corpus striatum involvement on DWI and high serum ammonia levels in patients with UCD.

Clinical and Biochemical Profiles of Filipino Patients with Distal Urea Cycle Disorders Detected by Abnormal Expanded Newborn Screening

Objective. The study is a retrospective review which provides preliminary data on the correlation between biochemical profiles and initial clinical manifestation of patients diagnosed to have argininosuccinate synthetase deficiency (ASSD) and argininosuccinate lyase deficiency (ASLD) detected by expanded newborn screening (ENBS).Methods. This is a study of five distal UCD patients initially detected by elevated citrulline on ENBS. Medical charts of the patients were reviewed. The initial clinical manifestations of the patients were correlated with results of biochemical tests.Results. There were four cases of ASLD and one case of ASSD reviewed in this study. All cases of ASLD were confirmed by the presence of argininosuccinic acid (ASA) in the urine metabolic screen (UMS). The plasma citrulline level of the ASSD patient is significantly elevated as compared to the ASLD patients (2,690 µmol/L; NV: 10-45 µmol/L). The ASSD patient and one ASLD patient were symptomatic within the first six days of life. Both presented with significantly elevated plasma ammonia, citrulline and glutamine levels. Three ASLD patients were asymptomatic on initial screening.Conclusion. ENBS has shown importance in the early detection and management of ASSD and ASLD. Early initiation of management may prevent hyperammonemic crises. Long term outcome studies are needed to look into the correlation of neurodevelopmental outcome with lifelong accumulation of citrulline and glutamine in ASSD and ASA in ASLD.

A Severe Neonatal Argininosuccinic Aciduria Case Investigated by 1H NMR Spectroscopy

The NMR urine analysis of a term newborn with severe general deterioration of the clinical state revealed the presence in high concentrations of orotic and argininosuccinic acids. The newborn was suspected for an intoxication-like inborn error of metabolism, and the urine samples were followed up by NMR spectroscopy for several days in order to assess the metabolic pattern. The identified markers led to a definitive biochemical diagnosis of argininosuccinic aciduria.