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BackgroundSphingosine-1-phosphate lyase insufficiency syndrome (SPLIS) is a recently recognized inborn error of metabolism associated with steroid-resistant nephrotic syndrome as well as adrenal insufficiency and immunological, neurological, and skin manifestations. SPLIS is caused by inactivating mutations in SGPL1, encoding the pyridoxal 5'phosphate-dependent enzyme sphingosine-1-phosphate lyase, which catalyzes the final step of sphingolipid metabolism. Some SPLIS patients have undergone kidney transplantation, and others have been treated with vitamin B6 supplementation. In addition, targeted therapies including gene therapy are in preclinical development. In anticipation of clinical trials, it will be essential to characterize the full spectrum and natural history of SPLIS. We performed a retrospective analysis of 76 patients in whom the diagnosis of SPLIS was established in a proband with at least one suggestive finding and biallelic SGPL1 variants identified by molecular genetic testing. The main objective of the study was to identify factors influencing survival in SPLIS subjects.ResultsOverall survival at last report was 50%. Major influences on survival included: (1) age and organ involvement at first presentation; (2) receiving a kidney transplant, and (3) SGPL1 genotype. Among 48 SPLIS patients with nephropathy who had not received a kidney transplant, two clinical subgroups were distinguished. Of children diagnosed with SPLIS nephropathy before age one (n = 30), less than 30% were alive 2 years after diagnosis, and 17% were living at last report. Among those diagnosed at or after age one (n = 18), ~ 70% were alive 2 years after diagnosis, and 72% were living at time of last report. SPLIS patients homozygous for the SPL R222Q variant survived longer compared to patients with other genotypes. Kidney transplantation significantly extended survival outcomes.ConclusionOur results demonstrate that SPLIS is a phenotypically heterogeneous condition. We find that patients diagnosed with SPLIS nephropathy in the first year of life and patients presenting with prenatal findings represent two high-risk subgroups, whereas patients harboring the R222Q SGPL1 variant fare better than the rest. Time to progression from onset of proteinuria to end stage kidney disease varies from less than one month to five years, and kidney transplantation may be lifesaving.

Background: Methylmalonic acidemia (MMA), type mut (0) is a rare type of genetic inborn error of metabolism (IEM) that is caused by aberrant malonyl-CoA mutase activity. Diagnosing IEM can be challenging due to its inherited onset and varying degrees of severity. Methods and results: In the present study, a consanguineous Pakistani family suspected of IEM was genetically analyzed using whole exome sequencing. A biallelic variant c.689 C > G (p.Thr230Arg) in MMUT was identified to be the causative factor of the disease, which helped in establishing the accurate diagnosis in the family to be MMA mut(0) type. On the basis of the genetic findings, the patient's condition was appropriately managed through a supportive nutrition plan and administration of oral L-carnitine. Conclusions: Identification of MMUT mutation through whole exome sequencing was helpful in solving the family and devising targeted management strategies. This study highlights the utility of genetic analysis in diagnosing and treating metabolic disorders like MMA in Pakistani inbred population. Highlights: In the present study, a consanguineous Pakistani family suspected of IEM was genetically analyzed using whole exome sequencing. A biallelic variant c.689 C > G (p.Thr230Arg) in MMUT was identified to be the causative factor of the disease, which helped in establishing the accurate diagnosis in the family to be MMA mut(0) type. [ABSTRACT FROM AUTHOR]

Background/Objectives: In heme degradation, biliverdin reductase catalyzes the conversion of biliverdin to bilirubin. Defects in the biliverdin reductase A gene (BLVRA) causing biliverdinuria are extraordinarily rare in humans, and this inborn error of metabolism has not been reported in other mammals. The objective of this study was to diagnose biliverdinuria and identify the causal BLVRA variants in two adult mixed-breed dogs with life-long green urine. One of the dogs also had an unexplained regenerative anemia and mild hepatopathy. Methods: Clinicopathological evaluations, urinary mass spectroscopy, and molecular genetic studies were performed. Urine metabolic screening identified increased biliverdin concentrations in both cases relative to control dogs. Results: Whole genome and Sanger sequencing revealed that each case was homozygous for large deletions in BLVRA: UU_Cfam_GSD_1.0/canFam4 chr18:6,532,022–6,551,313 (19,292 bp) in Case 1 and chr18:6,543,863–6,545,908 (2046 bp) in Case 2. These variants were predicted to result in major BLVRA truncations (ENSCAFT00805017018.1 p.[Lys117-Lys296del] and p.[Ala154fs], respectively) and loss of enzyme function. In a genomic variant database, 671 dogs from 63 breeds had coverage over these regions, ruling out homozygosity for the BLVRA deletions. A gene defect for the regenerative anemia in Case 1 was not discovered. Conclusions: While expected to be rare, genotyping for the BLVRA deletions can be used to identify other affected and carrier dogs. This study illustrates the use of targeted metabolic and genomic screening as key diagnostic tools to diagnose a rare metabolic disorder. These are the first confirmed cases of biliverdinuria caused by BLVRA defects in non-human mammals. [ABSTRACT FROM AUTHOR]

The article discusses childhood-onset hereditary spastic paraplegia (HSP) caused by biallelic variants in the COQ4 gene. A case study of a 6-year-old female of European ancestry with lower limb spasticity and delayed motor development is presented. Genetic testing revealed compound-heterozygous variants in COQ4, leading to a diagnosis of pure HSP. The study highlights the importance of reanalyzing genetic data and the potential therapeutic implications of CoQ10 supplementation for patients with COQ4 deficiency. [Extracted from the article]

Objective: To elucidate and give comprehensive review on the advances in disease modeling in metabolic inborn errors. Materials and Methods: Article search was done in October 10th 2022 in PubMed database, with keywords: "Metabolism "AND "inborn errors"AND "genomic" AND "cell lines" as well as "gene therapy" AND "Metabolism" AND "inborn errors" AND "genomic" from year 2018-2022. Results and Discussion: We got 44 articles that address disease modeling in inborn error of metabolism. Disease modeling is valuable for pathogenesis elucidation, which includes various diseases' modeling in vitro such as, Hermansky-Pudlak syndrome, familial hypercholesterolemia, hypomyelinating leukodystrophy, methylmalonic acidemia, propionic acidemia, neural ceroid lipofuscinosis type-2 disease, lysosomal storage disorder, and mucolipidoses type III alpha/beta. In addition, disease modeling in vivo includes phenylketonuria, Niemann-Pick disease type C1, and oculocutaneous albinism type 1. Conclusion: disease modeling in vitro and in vivo by various methods and advancement in gene editing using CRISPR/Cas9 are valuable for pathogenesis elucidation and prediction of metabolic error correction potential by gene editing, development of new therapeutic agents, and in the future may open new hopes for long term and permanent gene therapy treatment. [ABSTRACT FROM AUTHOR]

Highlights: The inaugural Clinical and Scientific Conference on Adenylosuccinate Synthetase 1 (ADSS1) myopathy was held on June 3, 2024, at the National Institutes of Health (NIH) National Center for Advancing Translational Sciences (NCATS) in Rockville, Maryland, USA. ADSS1 myopathy is an ultra-rare, inherited neuromuscular disease. Features of geographical patient clusters in South Korea, Japan, India and the United States of America were characterised and discussed. Pre-clinical animal and cell-based models were discussed, providing unique insight into disease pathogenesis. The biochemical pathogenesis was discussed, and potential therapeutic targets identified. Potential clinical and pre-clinical biomarkers were discussed. An ADSS1 myopathy consortium was established and a roadmap for therapeutic development created. [ABSTRACT FROM AUTHOR]

Abstract Glycerol kinase deficiency (GKD) is an X‐linked recessive disorder due to glycerol kinase (GK) gene mutations resulting in hyperglycerolermia, hyperglyceroluria, and “pseudohypertriglyceridemia.” In vivo glycerol metabolism has not been assessed in GKD. A 62‐year‐old man with suspected GKD and his extended family underwent whole exome sequencing and fasting blood work with two modes of lipid measurements: (1) standard lipase‐based methodology and (2) nuclear magnetic resonance (NMR). Two overnight fasted men with GKD and a heterozygote female carrier then underwent 13C3‐glycerol infusion. Affected family members had a novel two‐nucleotide deletion in exon 5 of the GK gene (c.373_374del). Compared to their family members (n = 14), men with GKD (n = 5) had significantly lower total cholesterol levels (3.72 ± 0.70 vs. 4.77 ± 0.85 mmol/L, p = 0.024). Compared to NMR, lipase‐based assays overreported triglycerides (5.28 ± 1.38 vs. 0.81 ± 0.32, mmol/L, p

Abstract Fructose‐1,6‐bisphosphatase (FBPase) deficiency is a rare, inborn error of metabolism, that causes hypoglycemia and lactic acidosis in response to inadequate glucose intake and/or high intakes of fructose, sucrose, or sorbitol. Pregnancy in women with FBPase deficiency puts them at high risk for metabolic decompensation due to increased glucose demands from the growing fetus. Here we report a 31‐year‐old primipara who was treated starting at 14 weeks gestation with a diet high in complex carbohydrates and low in fructose, sucrose, and sorbitol and close monitoring of glucose levels throughout her pregnancy. She delivered a healthy 2860 g baby at 37 weeks via vaginal delivery with no complications or hypoglycemia. At 5 months postpartum and 5 months of life, the patient and baby are doing well, although the patient experienced an episode of hypoglycemia and lactic acidosis at 4 months postpartum due to the increased metabolic demands of breastfeeding. This report adds to the limited case reports that discuss outcomes and proposed interventions during pregnancy in individuals with FBPase deficiency.

Abstract Background Sphingosine-1-phosphate lyase insufficiency syndrome (SPLIS) is a recently recognized inborn error of metabolism associated with steroid-resistant nephrotic syndrome as well as adrenal insufficiency and immunological, neurological, and skin manifestations. SPLIS is caused by inactivating mutations in SGPL1, encoding the pyridoxal 5’phosphate-dependent enzyme sphingosine-1-phosphate lyase, which catalyzes the final step of sphingolipid metabolism. Some SPLIS patients have undergone kidney transplantation, and others have been treated with vitamin B6 supplementation. In addition, targeted therapies including gene therapy are in preclinical development. In anticipation of clinical trials, it will be essential to characterize the full spectrum and natural history of SPLIS. We performed a retrospective analysis of 76 patients in whom the diagnosis of SPLIS was established in a proband with at least one suggestive finding and biallelic SGPL1 variants identified by molecular genetic testing. The main objective of the study was to identify factors influencing survival in SPLIS subjects. Results Overall survival at last report was 50%. Major influences on survival included: (1) age and organ involvement at first presentation; (2) receiving a kidney transplant, and (3) SGPL1 genotype. Among 48 SPLIS patients with nephropathy who had not received a kidney transplant, two clinical subgroups were distinguished. Of children diagnosed with SPLIS nephropathy before age one (n = 30), less than 30% were alive 2 years after diagnosis, and 17% were living at last report. Among those diagnosed at or after age one (n = 18), ~ 70% were alive 2 years after diagnosis, and 72% were living at time of last report. SPLIS patients homozygous for the SPL R222Q variant survived longer compared to patients with other genotypes. Kidney transplantation significantly extended survival outcomes. Conclusion Our results demonstrate that SPLIS is a phenotypically heterogeneous condition. We find that patients diagnosed with SPLIS nephropathy in the first year of life and patients presenting with prenatal findings represent two high-risk subgroups, whereas patients harboring the R222Q SGPL1 variant fare better than the rest. Time to progression from onset of proteinuria to end stage kidney disease varies from less than one month to five years, and kidney transplantation may be lifesaving.

Abstract This study aimed to analyze whether early‐treated adults with phenylketonuria (PKU) can subjectively sense high phenylalanine (Phe) concentrations and whether a possible impact of Phe on objective measures of cognitive performance and mood reflects patients' self‐perception. Data from the PICO study, a randomized, placebo‐controlled, double‐blind, crossover trial, were analyzed. Twenty‐eight adults with PKU received either Phe capsules or placebo in two 4‐week intervention periods in a randomized order, with a 4‐week washout in between. The median Phe level increased from 852 μmol/L (interquartile range: 345) to 1455 μmol/L (interquartile range: 369). Neuropsychological assessments were performed at four study visits. At the end of the last study visit, patients were asked whether they could discern the Phe intervention period. Seven of 28 (25%) patients stated that they could not discern between the Phe and the placebo period. Twenty‐one of 28 (75%) patients subjectively thought to sense high Phe levels. Of the 21 patients, 12 (57%) correctly identified the Phe period, whereas 9 (43%) received placebo at the time when they thought they would receive the high Phe load. Binomial tests showed that the probability of 12 out of 21 is p = 0.140, and 12 out of 28 is p = 0.113. The “Right‐Guess” group showed significantly higher Phe changes than the “Wrong‐Guess” group. Cognitive performance and standardized mood assessment did not significantly differ, and both groups reported similar subjective negative impact on cognition and mood. In conclusion, adults with early‐treated PKU cannot effectively identify high Phe levels, although some individuals may be able to perceive more pronounced increases in Phe levels.

The balance between a protective and a destructive immune response can be precarious, as exemplified by inborn errors in nucleotide metabolism. This class of inherited disorders, which mimics infection, can result in systemic injury and severe neurologic outcomes. The most common of these disorders is Aicardi Goutières syndrome (AGS). AGS results in a phenotype similar to "TORCH" infections (Toxoplasma gondii, Other [Zika virus (ZIKV), human immunodeficiency virus (HIV)], Rubella virus, human Cytomegalovirus [HCMV], and Herpesviruses), but with sustained inflammation and ongoing potential for complications. AGS was first described in the early 1980s as familial clusters of "TORCH" infections, with severe neurology impairment, microcephaly, and basal ganglia calcifications (Aicardi & Goutières, Ann Neurol, 1984;15:49–54) and was associated with chronic cerebrospinal fluid (CSF) lymphocytosis and elevated type I interferon levels (Goutières et al., Ann Neurol, 1998;44:900–907). Since its first description, the clinical spectrum of AGS has dramatically expanded from the initial cohorts of children with severe impairment to including individuals with average intelligence and mild spastic paraparesis. This broad spectrum of potential clinical manifestations can result in a delayed diagnosis, which families cite as a major stressor. Additionally, a timely diagnosis is increasingly critical with emerging therapies targeting the interferon signaling pathway. Despite the many gains in understanding about AGS, there are still many gaps in our understanding of the cell‐type drivers of pathology and characterization of modifying variables that influence clinical outcomes and achievement of timely diagnosis. [ABSTRACT FROM AUTHOR]

Background: Liver transplantation (LT) has been proposed as a viable treatment option for selected methylmalonic acidemia (MMA) patients. However, there are still controversies regarding the therapeutic value of LT for MMA. The systematic assessment of health-related quality of life (HRQoL)-targeted MMA children before and after LT is also undetermined. This study aimed to comprehensively assess the long-term impact of LT on MMA, including multiorgan sequelae and HRQoL in children and families. Methods: We retrospectively evaluated 15 isolated MMA patients undergoing LT at our institution between June 2013 and March 2022. Pre- and post-transplant data were compared, including metabolic profiles, neurologic consequences, growth parameters, and HRQoL. To further assess the characteristics of the HRQoL outcomes in MMA, we compared the results with those of children with biliary atresia (BA). Results: All patients had early onset MMA, and underwent LT at a mean age of 4.3 years. During 1.3–8.2 years of follow-up, the patient and graft survival rates were 100%. Metabolic stability was achieved in all patients with liberalized dietary protein intake. There was a significant overall improvement in height Z scores (P = 0.0047), and some preexisting neurological complications remained stable or even improved after LT. On the Pediatric Quality of Life Inventory (PedsQL™) generic core scales, the mean total, physical health, and psychosocial health scores improved significantly posttransplant (P < 0.05). In the family impact module, higher mean scores were noted for all subscales post-LT, especially family function and daily activities (P < 0.01). However, the total scores on the generic core scales and transplant module were significantly lower (Cohen's d = 0.57–1.17) when compared with BA recipients. In particular, social and school functioning (Cohen's d = 0.86–1.76), treatment anxiety, and communication (Cohen's d = 0.99–1.81) were far behind, with a large effect size. Conclusions: This large single-center study of the mainland of China showed an overall favorable impact of LT on isolated MMA in terms of long-term survival, metabolic control, and HRQoL in children and families. The potential for persistent neurocognitive impairment and inherent metabolic fragility requires long-term special care. F92j7K3vL8yMEEzsip9Zc8 Video Abstract (MP4 153780 KB) [ABSTRACT FROM AUTHOR]

Nonketotic hyperglycinemia (NKH) is a relatively well‐characterized inborn error of metabolism that results in a combination of lethargy, hypotonia, seizures, developmental arrest, and, in severe cases, death early in life. Three genes encoding components of the glycine cleavage enzyme system—GLDC, AMT, and GCSH—are independently associated with NKH. We report on a patient with severe NKH in whom the homozygous pathogenic variant in AMT (NM_000481.3):c.602_603del (p.Lys201Thrfs*75) and the homozygous likely pathogenic variant in GLDC(NM_000170.2):c.2852C>A (p.Ser951Tyr) were both identified. Our patient demonstrates a novel combination of two homozygous disease‐causing variants impacting the glycine cleavage pathway at two different components, and elicits management‐ and genetic counseling‐related challenges for the family. [ABSTRACT FROM AUTHOR]

Fructose-1, 6- bisphosphatase deficiency is a rare autosomal recessive inborn error of fructose metabolism which mainly affects gluconeogenesis. It often presents with ketotic hypoglycemia and lactic acidosis, with hyperventilation. The disease has a high mortality rate when undiagnosed.Here we report a case of this rare disorder, referred to our hospital in Western Nepal, diagnosed originally as pneumonia. The patient presented in respiratory distress with severe metabolic acidosis and dehydration. She also demonstrated hypoglycemia, hypernatremia, coagulation dysfunction and albuminuria, all of which gradually improved, though her lactate remained consistently elevated. This led to investigation of urinary ketones which were positive suggesting a defect in the metabolism of carbohydrates. Urine organic acid profile and whole exome sequencing finally confirmed the diagnosis of Fructose-1, 6- bisphosphatase deficiency. To our knowledge this is the first case report of this disease diagnosed in Nepal.

Background: Propionic acidemia (PA) is an inborn error of metabolism (IEM) that typically presents in the newborn. The Amish of North America have an increased prevalence of PA due to a founder variant in the PCCB gene. The Amish PA phenotype is variable, and some individuals remain asymptomatic and undiagnosed until adulthood. Additionally, there are limited reports of pregnancy outcomes in Amish individuals with PA. Methods: A retrospective single center chart review was completed on sixty Amish individuals with PA to identify individuals diagnosed as adults (18 years or older) and pregnancy outcomes. We assessed age at diagnosis, reason for PA testing, medical history prior to diagnosis including developmental delay, seizure, protein intolerance, cardiac symptoms, and anxiety. Following the diagnosis, we assessed the prevalence of prolonged QTc and dilated cardiomyopathy. We assessed our cohort for number of pregnancies, pregnancy outcomes, and peripartum complications. Results: Nine out of sixty individuals (15 %) were diagnosed with PA as adults. A family member with PA was the most common reason to prompt genetic testing. Cardiac symptoms were present in six of nine individuals prior to diagnosis. Three individuals diagnosed as adults had dilated cardiomyopathy and one underwent cardiac transplant. There were twenty-one pregnancies in six women with eighteen successful deliveries and three miscarriages. Two women developed peripartum cardiomyopathy. There were no acute maternal decompensations. Conclusion: Our work supports the consideration that all Amish newborns be screened for PA with molecular testing to enable early diagnosis. The stark difference in peripartum outcomes requires further prospective work to ensure appropriate monitoring throughout pregnancy while respecting individual values and autonomy.

Stored dried blood spots (DBSs) give significant specimens for retrospective detection of inborn errors of metabolisms (IEM) including for validation studies through newborn screening (NBS) programs. Inborn errors of metabolisms have severe medical outcomes in infants and newborns, and initial identification and errors of metabolism treatment can lessen morbidity and mortality. The study investigated the impacts of different conditions for storage (humidity and temperature) experienced throughout the stored dried blood specimen gathering and transportation of the metabolites tested in the NBS program. Stored dried blood spots collected from healthy newborns and kept at room temperatures (RT, 22–25 °C), 37 °C, and 4 °C were examined for acylcarnitine and amino acid panels for 5 days, 1 month, and 2 months using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The outcomes display the decay patterns of amino acids and acylcarnitines at different temperatures and elevated humidity. The study findings indicate that humidity and temperature during sample transit affect the integrity of stored dried blood within a short period. The packaging of blood spots should be done correctly and sent to a newborn screening laboratory immediately. Including a maintained stored dried blood kept along with earlier specimens utilized in retrospective diagnostic cohort studies would give insights into the sample's condition. [ABSTRACT FROM AUTHOR]

Although a rare cause of neonatal seizures, inborn errors of metabolism (IEMs) remain an essential component of a comprehensive differential diagnosis for poorly controlled neonatal epilepsy. Diagnosing neonatal-onset metabolic conditions proves a difficult task for clinicians; however, routine state newborn screening panels now include many IEMs. Three in particular—pyridoxine-dependent epilepsy, maple syrup urine disease, and Zellweger spectrum disorders—are highly associated with neonatal epilepsy and neurocognitive injury yet are often misdiagnosed. As research surrounding biomarkers for these conditions is emerging and gene sequencing technologies are advancing, clinicians are beginning to better establish early identification strategies for these diseases. In this literature review, the authors aim to present clinicians with an innovative clinical guide highlighting IEMs associated with neonatal-onset seizures, with the goal of promoting quality care and safety. [ABSTRACT FROM AUTHOR]

Aromatic l-amino acid decarboxylase deficiency (AADC-DY) is caused by one or more mutations in the DDC gene, resulting in the deficit in catecholamines and serotonin neurotransmitters. The disease has limited therapeutic options with relatively poor clinical outcomes. Accumulated evidence suggests the involvement of neurodegenerative mechanisms in the etiology of AADC-DY. In the absence of neurotransmitters' neuroprotective effects, the accumulation and the chronic presence of several neurotoxic metabolites including 4-dihydroxy-L-phenylalanine, 3-methyldopa, and homocysteine, in the brain of subjects with AADC-DY, promote oxidative stress and reduce the cellular antioxidant and methylation capacities, leading to glial activation and mitochondrial dysfunction, culminating to neuronal injury and death. These pathophysiological processes have the potential to hinder the clinical efficacy of treatments aimed at increasing neurotransmitters' synthesis and or function. This review describes in detail the mechanisms involved in AADC-DY neurodegenerative etiology, highlighting the close similarities with those involved in other neurodegenerative diseases. We then offer novel strategies for the treatment of the disease with the objective to either reduce the level of the metabolites or counteract their prooxidant and neurotoxic effects. These treatment modalities used singly or in combination, early in the course of the disease, will minimize neuronal injury, preserving the functional integrity of neurons, hence improving the clinical outcomes of both conventional and unconventional interventions in AADC-DY. These modalities may not be limited to AADC-DY but also to other metabolic disorders where a specific mutation leads to the accumulation of prooxidant and neurotoxic metabolites. [ABSTRACT FROM AUTHOR]

Background: Congenital disorders of glycosylation (CDG) are a type of inborn error of metabolism (IEM) resulting from defects in glycan synthesis or failed attachment of glycans to proteins or lipids. One rare type of CDG is caused by homozygous or compound heterozygous loss‐of‐function variants in mannosidase alpha class 2B member 2 (MAN2B2). To date, only two cases of MAN2B2‐CDG have been reported worldwide. Methods: Trio whole‐exome sequencing (Trio‐WES) was conducted to screen for candidate variants. N‐glycan profiles were measured by liquid chromatography–tandem mass spectrometry (LC–MS/MS). MAN2B2 expression was evaluated by western blotting. MX dynamin like GTPase 1 (MX1) function was estimated via Thogoto virus (THOV) minireplicon assay. Results: Trio‐WES identified compound heterozygous MAN2B2 (hg19, NM_015274.1) variants (c.384G>T; c.926T>A) in a CDG patient. This patient exhibited metabolic abnormalities, symptoms of digestive tract dysfunction, infection, dehydration, and seizures. Novel immune dysregulation characterized by abnormal lymphocytes and immunoglobulin was observed. The MAN2B2 protein level was not affected, while LC–MS/MS showed obvious disruption of N‐glycans and N‐linked glycoproteins. Conclusion: We described a CDG patient with novel phenotypes and disruptive N‐glycan profiling caused by compound heterozygous MAN2B2 variants (c.384G>T; c.926T>A). Our findings broadened both the genetic and clinical spectra of CDG. [ABSTRACT FROM AUTHOR]

The pathophysiology of nonketotic hyperglycinemia (NKH), a rare neuro-metabolic disorder associated with severe brain malformations and life-threatening neurological manifestations, remains incompletely understood. Therefore, a valid human neural model is essential. We aimed to investigate the impact of GLDC gene variants, which cause NKH, on cellular fitness during the differentiation process of human induced pluripotent stem cells (iPSCs) into iPSC-derived astrocytes and to identify sustainable mechanisms capable of overcoming GLDC deficiency. We developed the GLDC27-FiPS4F-1 line and performed metabolomic, mRNA abundance, and protein analyses. This study showed that although GLDC27-FiPS4F-1 maintained the parental genetic profile, it underwent a metabolic switch to an altered serine–glycine–one-carbon metabolism with a coordinated cell growth and cell cycle proliferation response. We then differentiated the iPSCs into neural progenitor cells (NPCs) and astrocyte-lineage cells. Our analysis showed that GLDC-deficient NPCs had shifted towards a more heterogeneous astrocyte lineage with increased expression of the radial glial markers GFAP and GLAST and the neuronal markers MAP2 and NeuN. In addition, we detected changes in other genes related to serine and glycine metabolism and transport, all consistent with the need to maintain glycine at physiological levels. These findings improve our understanding of the pathology of nonketotic hyperglycinemia and offer new perspectives for therapeutic options. [ABSTRACT FROM AUTHOR]

• Exome data of DEE patient revealed compound heterozygous mutations (p.Asp257Asn and p.Arg262Cys) in the GOT2 gene. • Sanger sequencing showed that p.Asp257Asn was inherited paternally and p.Arg262Cys maternally. • The mutations disrupt evolutionarily conserved domains of the enzyme, impacting protein stability and structure. • The fifth DEE patient was reported with mutations in the GOT2 gene. Developmental and Epileptic Encephalopathies (DEEs) are rare neurological disorders characterized by early-onset medically resistant epileptic seizures, structural brain malformations, and severe developmental delays. These disorders can arise from mutations in genes involved in vital metabolic pathways, including those within the brain. Recent studies have implicated defects in the mitochondrial malate aspartate shuttle (MAS) as potential contributors to the clinical manifestation of infantile epileptic encephalopathy. Although rare, mutations in MDH1, MDH2, AGC1 , or GOT2 genes have been reported in patients exhibiting neurological symptoms such as global developmental delay, epilepsy, and progressive microcephaly. In this study, we employed exome data analysis of a patient diagnosed with DEE, focusing on the screening of 1896 epilepsy-related genes listed in the HPO and ClinVar databases. Sanger sequencing was subsequently conducted to validate and assess the inheritance pattern of the identified variants within the family. The evolutionary conservation scores of the mutated residues were evaluated using the ConSurf Database. Furthermore, the impacts of the causative variations on protein stability were analyzed through I-Mutant and MuPro bioinformatic tools. Structural comparisons between wild-type and mutant proteins were performed using PyMOL, and the physicochemical effects of the mutations were assessed using Project Hope. Exome data analysis unveiled the presence of novel compound heterozygous mutations in the GOT2 gene coding for mitochondrial glutamate aspartate transaminase. Sanger sequencing confirmed the paternal inheritance of the p.Asp257Asn mutation and the maternal inheritance of the p.Arg262Cys mutation. The affected individual exhibited plasma metabolic disturbances, including hyperhomocysteinemia, hyperlactatemia, and reduced levels of methionine and arginine. Detailed bioinformatic analysis indicated that the mutations were located within evolutionarily conserved domains of the enzyme, resulting in disruptions to protein stability and structure. Herein, we describe a case with DEE82 (MIM: # 618721) with pathologic novel biallelic mutations in the GOT2 gene. Early genetic diagnosis of metabolic epilepsies is crucial for long-term neurodevelopmental improvements and seizure control as targeted treatments can be administered based on the affected metabolic pathways. [ABSTRACT FROM AUTHOR]

Sanfilippo syndrome (Mucopolysaccharidosis type III or MPS III) is a recessively inherited neurodegenerative lysosomal storage disorder. Mutations in genes encoding enzymes in the heparan sulphate degradation pathway lead to the accumulation of partially degraded heparan sulphate, resulting ultimately in the development of neurological deficits. Mutations in the gene encoding the membrane protein heparan‐α‐glucosaminide N‐acetyltransferase (HGSNAT; EC2.3.1.78) cause MPS IIIC (OMIM#252930), typified by impaired cognition, sleep–wake cycle changes, hyperactivity and early death, often before adulthood. The precise disease mechanism that causes symptom emergence remains unknown, posing a significant challenge in the development of effective therapeutics. As HGSNAT is conserved in Drosophila melanogaster, we now describe the creation and characterisation of the first Drosophila models of MPS IIIC. Flies with either an endogenous insertion mutation or RNAi‐mediated knockdown of hgsnat were confirmed to have a reduced level of HGSNAT transcripts and age‐dependent accumulation of heparan sulphate leading to engorgement of the endo/lysosomal compartment. This resulted in abnormalities at the pre‐synapse, defective climbing and reduced overall activity. Altered circadian rhythms (shift in peak morning activity) were seen in hgsnat neuronal knockdown lines. Further, when hgsnat was knocked down in specific glial subsets (wrapping, cortical, astrocytes or subperineural glia), impaired climbing or reduced activity was noted, implying that hgsnat function in these specific glial subtypes contributes significantly to this behaviour and targeting treatments to these cell groups may be necessary to ameliorate or prevent symptom onset. These novel models of MPS IIIC provide critical research tools for delineating the key cellular pathways causal in the onset of neurodegeneration in this presently untreatable disorder. [ABSTRACT FROM AUTHOR]

Gaucher disease (GD) is mainly caused by glucocerebrosidase (GCase) enzyme deficiency due to genetic variations in the GBA1 gene leading to the toxic accumulation of sphingolipids in various organs, which causes symptoms such as anemia, thrombocytopenia, hepatosplenomegaly, and neurological manifestations. GD is clinically classified into the non-neuronopathic type 1, and the acute and chronic neuronopathic forms, types 2 and 3, respectively. In addition to the current approved GD medications, the repurposing of Ambroxol (ABX) has emerged as a prospective enzyme enhancement therapy option showing its potential to enhance mutated GCase activity and reduce glucosylceramide accumulation in GD-affected tissues of different GBA1 genotypes. The variability in response to ABX varies across different variants, highlighting the diversity in patients' therapeutic outcomes. Its oral availability and safety profile make it an attractive option, particularly for patients with neurological manifestations. Clinical trials are essential to explore further ABX's potential as a therapeutic medication for GD to encourage pharmaceutical companies' investment in its development. This review highlights the potential of ABX as a pharmacological chaperone therapy for GD and stresses the importance of addressing response variability in clinical studies to improve the management of this rare and complex disorder. [ABSTRACT FROM AUTHOR]

Inborn errors of metabolism (IEM) and endocrine disorders are common genetic conditions in the Saudi population with the incidence rate often underestimated. Newborn screening (NBS) using various disease panels provides the first line in the early detection and intervention among infants with a high risk of IEM. Here we aim to assess the incidence of screening disorders and provide an overview of the NBS program at the Ministry of Health Tertiary Care King Fahad Medical City. Dried blood spots (DBS) from 40,965 newborn infants collected on the second day after birth were analyzed for 20 disorders. The total number of positive screen (“repeat”) samples over 10 years was about 1% (n = 382/40,965). The true positive result rate was 15.3% (n = 46/301) with the recall rates of individual disorders ranging from 0.26% (95% CI, 0.17–0.69) to 2.6% (95% CI, 2.19–3.05). The false positive result rate was 84.7% (n = 255/301) with biotinidase activity found to be the most common cause of the second sample repeat. The overall incidence of the screened diseases was 1:891 (95% CI, 11.61–12.47). CH and CAH are the most prevalent among endocrine disorders with an incidence of 1:4097 (95% CI, 2.19–3.05), and PA and ASA among the IEM with an incidence of 1:10,241 (95% CI, 0.09–0.95). In summary, we provide updated data and our experience on the incidence of various IEM and endocrine disorders among the Saudi population, highlight the role of false positive results of biotinidase activity that can increase the recall rate and lead to overestimation of the incidence data, and recommend multicenter studies to achieve a successful national NBS program.

Gaucher disease (GD) is mainly caused by glucocerebrosidase (GCase) enzyme deficiency due to genetic variations in the GBA1 gene leading to the toxic accumulation of sphingolipids in various organs, which causes symptoms such as anemia, thrombocytopenia, hepatosplenomegaly, and neurological manifestations. GD is clinically classified into the non-neuronopathic type 1, and the acute and chronic neuronopathic forms, types 2 and 3, respectively. In addition to the current approved GD medications, the repurposing of Ambroxol (ABX) has emerged as a prospective enzyme enhancement therapy option showing its potential to enhance mutated GCase activity and reduce glucosylceramide accumulation in GD-affected tissues of different GBA1 genotypes. The variability in response to ABX varies across different variants, highlighting the diversity in patients’ therapeutic outcomes. Its oral availability and safety profile make it an attractive option, particularly for patients with neurological manifestations. Clinical trials are essential to explore further ABX’s potential as a therapeutic medication for GD to encourage pharmaceutical companies’ investment in its development. This review highlights the potential of ABX as a pharmacological chaperone therapy for GD and stresses the importance of addressing response variability in clinical studies to improve the management of this rare and complex disorder.

Background: Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH). The disease may present clinically with seizures, developmental delay, hyperactivity, autistic symptoms, blue eyes, rough and dry skin, albinism or blond hair and skin and a "musty odor" to the baby's urine and sweat. Aim of the Work: To evaluate management of phenylketonuria in infants and children. Program and methods: All patients diagnosed as phenylketonuria based on screening program, clinical and laboratory findings by measuring phenyl alanine level in the blood were retrospectively assessed through checking the files of patients at Assiut Genetic Counseling Centre and Al-Azhar Assiut University Hospital from 1st January 2016 to 28th February 2021, All files of patients were evaluated through full history taking, general and complete neurological examination and developmental assessment, serum phenyl alanine and tetrahydrobiopterin loading test was done in some cases. Intelligent Question (IQ), Electroencephalogram (EEG), Childhood Autistic Rating Scale (CARS), Attention Deficit Hyperactivity Disorder (ADHD) test and Brain Magnetic Resonance Imaging (MRI) were done in some cases. Results: In our study we estimated 400 cases retrospectively with phenylketonuria, 240 of them were found to be less than 6 months old (60%) diagnosed by screening while 160 of them ages more than 6 months (40%) diagnosed with clinical suspicion plus elevated serum phenyl alanine with mean age ± SD (1.99± 1.32) years. 204 cases were males (51%) and 196 cases were females (49%). 276 cases (69%) lived in rural areas and 124 cases (31%) lived in urban areas. 230 cases (57.5%) were offsprings of consanguineous parents. 250 cases (62.5%) had similar condition in their families. 160 cases (40%) were diagnosed by clinical presentation which included blond hair and other findings as follows: blond hair and autism in 24 cases (15%), blond hair and mental retardation in 60 cases (37.5%), blond hair and hyperactivity in 34 cases (21.25%), blond hair and seizures 29 in cases (18.125%), blond hair and bad odor urine 13 cases (8.125%). 132 cases (33%) had Phenyl alanine (Phe) level more than 1200µmol/L (classical PKU), 107 cases (26.8%) had Phe level between 900&1200µmol/L (moderate PKU) and most of them 161 cases (40.3%) had Phe level between 600&900µmol/L (mild PKU). 308 cases (77%) were compliant to dietary supplement and healthcare recommendations and 92 cases (23%) were non-compliant. Conclusion: Mild PKU was the most common form (40%) followed by the classic form (33%). Most of diagnosed cases of PKU asked for dietary supplementation and health care recommendations (77%). The development of Egyptian neonatal screening programs demonstrated how effective treatment can lead to a near normal outcome for affected individuals. [ABSTRACT FROM AUTHOR]

The c.1222C>T (p.Arg408Trp) variant in the phenylalanine hydroxylase gene (PAH) is the most frequent cause of phenylketonuria (PKU), the most common inborn error of metabolism. This autosomal-recessive disorder is characterized by accumulation of blood phenylalanine (Phe) to neurotoxic levels. Using real-world data, we observed that despite dietary and medical interventions, most PKU individuals harboring at least one c.1222C>T variant experience chronic, severe Phe elevations and do not comply with Phe monitoring guidelines. Motivated by these findings, we generated an edited c.1222C>T hepatocyte cell line and humanized c.1222C>T mouse models, with which we demonstrated efficient in vitro and in vivo correction of the variant with prime editing. Delivery via adeno-associated viral (AAV) vectors reproducibly achieved complete normalization of blood Phe levels in PKU mice, with up to 52% whole-liver corrective PAH editing. These studies validate a strategy involving prime editing as a potential treatment for a large proportion of individuals with PKU. [Display omitted] The PAH c.1222C>T variant is the most frequent variant reported in phenylketonuria (PKU) individuals. Here, the authors show these individuals have poor metabolic control, and they use prime editing, delivered by adeno-associated viral vectors, to directly correct the variant in the liver in humanized PKU mice and definitively treat the disease. [ABSTRACT FROM AUTHOR]

• Mortality among Indian children with infantile epileptic spasms syndrome seems to be comparable with developed countries. • The commonest cause of mortality observed among children with infantile epileptic spasms syndrome is sepsis. • Presence of seizures other than epileptic spasms is associated with lower survival time. • Presence of inborn error of metabolism as etiology is associated with lower survival time. • Children with idiopathic IESS have good survival prospects. The existing literature indicates a higher risk of mortality among children with Infantile epileptic spasms syndrome (IESS). Our aim was to find the mortality pattern and factors that affect survival among children with IESS. Children with IESS who had age of onset between one month and 24 months were included. The primary outcome was survival. We used Kaplan-Meier estimates for survival analysis and Cox regression analyses to evaluate possible factors associated with mortality. During the follow-up period (120 months), 19/160 children (11.9%) expired. Three children expired in the first week after initiation of ACTH. There were six deaths (3.8%; 31.6% of deaths), within two years. Clinical findings and laboratory investigations revealed the cause of death to be severe pneumonia in ten children. Three died of severe sepsis. Four died due to metabolic crisis and two children died due to probable Sudden unexpected death in epilepsy (SUDEP). On multivariable analysis, mortality was predicted by 'presence of seizures other than spasms' and an inborn error of metabolism (IEM) as the underlying cause. None of the children in the idiopathic group died. Survival in our single center cohort with IESS was good in comparison to previous studies. Considering that pneumonia and sepsis were the most common cause of mortality that we detected, steps for prevention of sepsis might be worth considering in these children. Presence of seizures other than epileptic spasms, and an IEM should prompt the physician to let the family know that risk of mortality is high. [ABSTRACT FROM AUTHOR]

Lysinuric protein intolerance (LPI) is a rare inborn error of metabolism (IEM), classified as an inherited aminoaciduria, caused by mutations in the SLC7A7 gene, leading to a defective cationic amino acid transport. The metabolic adaptations to the demands of pregnancy and delivery cause significant physiological stress, so those patients affected by IEM are at greater risk of decompensation. A 28-year-old woman with LPI had experienced 3 early miscarriages. While pregnancy was finally achieved, diverse nutritional and medical challenges emerged (food aversion, intrauterine growth restriction, bleeding risk, and preeclampsia suspicion), which put both the mother and the fetus at risk. Moreover, the patient requested a natural childbirth (epidural-free, delayed cord clamping). Although the existence of multiple safety concerns rejected this approach at first, the application of novel strategies made a successful delivery possible. This case reinforces that the woman's wish for a non-medicated, low-intervention natural birth should not be automatically discouraged because of an underlying complex metabolic condition. Achieving a successful pregnancy is conceivable thanks to the cooperation of interdisciplinary teams, but it is still important to consider the risks beforehand in order to be prepared for possible additional complications. [ABSTRACT FROM AUTHOR]

A number of hereditary ataxias are caused by inborn errors of metabolism (IEM), most of which are highly heterogeneous in their clinical presentation. Prompt diagnosis is important because disease-specific therapies may be available. In this review, we offer a comprehensive overview of metabolic ataxias summarized by disease, highlighting novel clinical trials and emerging therapies with a particular emphasis on first-in-human gene therapies. We present disease-specific treatments if they exist and review the current evidence for symptomatic treatments of these highly heterogeneous diseases (where cerebellar ataxia is part of their phenotype) that aim to improve the disease burden and enhance quality of life. In general, a multimodal and holistic approach to the treatment of cerebellar ataxia, irrespective of etiology, is necessary to offer the best medical care. Physical therapy and speech and occupational therapy are obligatory. Genetic counseling is essential for making informed decisions about family planning. [ABSTRACT FROM AUTHOR]

Background: Monogenetic inborn errors of metabolism cause a wide phenotypic heterogeneity that may even differ between family members carrying the same genetic variant. Computational modelling of metabolic networks may identify putative sources of this inter-patient heterogeneity. Here, we mainly focus on medium-chain acyl-CoA dehydrogenase deficiency (MCADD), the most common inborn error of the mitochondrial fatty acid oxidation (mFAO). It is an enigma why some MCADD patients—if untreated—are at risk to develop severe metabolic decompensations, whereas others remain asymptomatic throughout life. We hypothesised that an ability to maintain an increased free mitochondrial CoA (CoASH) and pathway flux might distinguish asymptomatic from symptomatic patients. Results: We built and experimentally validated, for the first time, a kinetic model of the human liver mFAO. Metabolites were partitioned according to their water solubility between the bulk aqueous matrix and the inner membrane. Enzymes are also either membrane-bound or in the matrix. This metabolite partitioning is a novel model attribute and improved predictions. MCADD substantially reduced pathway flux and CoASH, the latter due to the sequestration of CoA as medium-chain acyl-CoA esters. Analysis of urine from MCADD patients obtained during a metabolic decompensation showed an accumulation of medium- and short-chain acylcarnitines, just like the acyl-CoA pool in the MCADD model. The model suggested some rescues that increased flux and CoASH, notably increasing short-chain acyl-CoA dehydrogenase (SCAD) levels. Proteome analysis of MCADD patient-derived fibroblasts indeed revealed elevated levels of SCAD in a patient with a clinically asymptomatic state. This is a rescue for MCADD that has not been explored before. Personalised models based on these proteomics data confirmed an increased pathway flux and CoASH in the model of an asymptomatic patient compared to those of symptomatic MCADD patients. Conclusions: We present a detailed, validated kinetic model of mFAO in human liver, with solubility-dependent metabolite partitioning. Personalised modelling of individual patients provides a novel explanation for phenotypic heterogeneity among MCADD patients. Further development of personalised metabolic models is a promising direction to improve individualised risk assessment, management and monitoring for inborn errors of metabolism. [ABSTRACT FROM AUTHOR]

Human milk (HM) offers important nutritional benefits. However, except for phenylketonuria (PKU), there are little data on optimal levels of consumption of HM and a special formula free of disease-related amino acids (SF-AA) in infants with inborn errors of metabolism of amino acids and proteins (IEM-AA-P). We designed a spreadsheet to calculate the amounts of SF-AA and HM required to cover amino acid, protein, and energy needs in patients with the nine main IEM-AA-P in infants aged under 6 months. Upon entering the infant's weight and the essential amino acid or intact protein requirements for the specific IEM, the spreadsheet calculates the corresponding required volume of HM based on the amino acid concentration in HM. Next, the theoretical daily fluid intake (typical range, 120–200 mL/kg/day) is entered, and the estimated daily fluid intake is calculated. The required daily volume of SF-AA is calculated as the difference between the total fluid intake value and the calculated volume of HM. The spreadsheet allows for the introduction of a range of requirements based on the patient's metabolic status, and includes the option to calculate the required volume of expressed HM, which may be necessary in certain conditions such as MMA/PA and UCD. In cases in which breastfeeding on demand is feasible, the spreadsheet determines the daily amount of SF-AA divided over 6–8 feeds, assuming that SF-AA is administered first, followed by HM as needed. Intake data calculated by the spreadsheet should be evaluated in conjunction with data from clinical and nutritional analyses, which provide a comprehensive understanding of the patient's nutritional status and help guide individualized dietary management for the specific IEM. [ABSTRACT FROM AUTHOR]

Dogs provide highly valuable models of human disease due to the similarity in phenotype presentation and the ease of genetic analysis. Seven Saluki puppies were investigated for neurological abnormalities including seizures and altered behavior. Magnetic resonance imaging showed a diffuse, marked reduction in cerebral cortical thickness, and symmetrical T2 hyperintensity in specific brain regions. Cerebral cortical atrophy with vacuolation (status spongiosus) was noted on necropsy. Genome-wide association study of 7 affected and 28 normal Salukis revealed a genome-wide significantly associated region on CFA 35. Whole-genome sequencing of three confirmed cases from three different litters revealed a homozygous missense variant within the aldehyde dehydrogenase 5 family member A1 (ALDH5A1) gene (XM_014110599.2: c.866G>A; XP_013966074.2: p.(Gly288Asp). ALDH5A1 encodes a succinic semialdehyde dehydrogenase (SSADH) enzyme critical in the gamma-aminobutyric acid neurotransmitter (GABA) metabolic pathway. Metabolic screening of affected dogs showed markedly elevated gamma-hydroxybutyric acid in serum, cerebrospinal fluid (CSF) and brain, and elevated succinate semialdehyde in urine, CSF and brain. SSADH activity in the brain of affected dogs was low. Affected Saluki dogs had striking similarities to SSADH deficiency in humans although hydroxybutyric aciduria was absent in affected dogs. ALDH5A1-related SSADH deficiency in Salukis provides a unique translational large animal model for the development of novel therapeutic strategies.

Abstract 3‐Methylglutaconyl‐CoA hydratase deficiency (MGA1) is a defect in leucine catabolism, which causes the accumulation of urinary 3‐methylglutaconate, with or without 3‐hydroxyisovalerate and 3‐methylglutarate. It is an ultra‐rare condition, with

There are concerns about muscle and bone health in patients with Phenylketonuria (PKU). Our aim was to compare muscle mass, function, and bone health among young adults with PKU who maintained or suspended dietary treatment. Methods: Three groups were considered—PKU-1: 10 patients who used a protein substitute (PS) without phenylalanine (Phe); PKU-2: 14 patients who used the PS without Phe until eighteen years old and then practiced mostly a vegan diet; and 24 matched healthy controls. A 24 h recall survey, blood parameters, body composition and bone mineral density through DEXA, rectus femoris thickness by ultrasound, hand grip strength, submaximal exercise test, and walking speed were assessed. Results: PKU-1 patients had lower hand grip strength than their matched controls, but no other differences. Compared to controls, the PKU-2 group had lower fat-free mass (p = 0.01), less spine and femoral bone mineral density (p = 0.04 and p < 0.01, respectively), and peak workload on the incremental test (p = 0.03). When comparing PKU groups, blood Phe levels were significantly lower in the PKU-1 group (p = 0.02). Conclusions: Among PKU patients, abandoning the dietary treatment and maintaining high blood Phe concentrations could be deleterious for muscles and bones. However, we cannot discard other causes of bone and muscle damage in these patients. [ABSTRACT FROM AUTHOR]

3-methylglutaconyl (3MGC) CoA hydratase (AUH) is the leucine catabolism pathway enzyme that catalyzes the hydration of trans-3MGC CoA to 3-hydroxy, 3-methylglutaryl (HMG) CoA. In several inborn errors of metabolism (IEM), however, metabolic dysfunction can drive this reaction in the opposite direction (the dehydration of HMG CoA). The recent discovery that trans-3MGC CoA is inherently unstable and prone to a series of non-enzymatic chemical reactions provides an explanation for 3MGC aciduria observed in these IEMs. Under physiological conditions, trans-3MGC CoA can isomerize to cis-3MGC CoA, which is structurally poised to undergo intramolecular cyclization with the loss of CoA, generating cis-3MGC anhydride. The anhydride is reactive and has two potential fates; (a) hydrolysis to yield cis-3MGC acid or (b) a reaction with lysine side-chain amino groups to 3MGCylate substrate proteins. An antibody elicited against a 3MGC hapten was employed to investigate protein acylation in incubations containing recombinant AUH, HMG CoA, and bovine serum albumin (BSA). The data obtained show that, as AUH dehydrates HMG CoA to trans-3MGC CoA, BSA is acylated. Moreover, α-3MGC IgG immunoblot signal intensity correlates with AUH concentration, HMG CoA substrate concentration, and incubation time. Thus, protein 3MGCylation may contribute to the phenotypic features associated with IEMs that manifest 3MGC aciduria. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) is an autosomal recessive inborn error of metabolism where high phenylalanine (Phe) concentrations cause irreversible intellectual disability that can be prevented by newborn screening and early treatment. Evidence suggests that PKU subjects not adherent to treatment could be at risk of insulin resistance (IR). We studied how Phe concentrations (PheCs) relate to IR using machine learning (ML) and derived potential biomarkers. In our cross-sectional study, we analyzed subjects with neonatal diagnoses of PKU, grouped as follows: 10 subjects who adhered to treatment (G1); 14 subjects who suspended treatment (G2); and 24 control subjects (G3). We analyzed plasma biochemical variables, as well as profiles of amino acids and acylcarnitines in dried blood spots (DBSs). Higher PheCs and plasma insulin levels were observed in the G2 group compared to the other groups. Additionally, a positive correlation between the PheCs and homeostatic measurement assessments (HOMA-IRs) was found, as well as a negative correlation between the HOMA-Sensitivity (%) and quantitative insulin sensitivity check index (QUICKI) scores. An ML model was then trained to predict abnormal HOMA-IRs using the panel of metabolites measured from DBSs. Notably, ranking the features' importance placed PheCs as the second most important feature after BMI for predicting abnormal HOMA-IRs. Our results indicate that low adherence to PKU treatment could affect insulin signaling, decrease glucose utilization, and lead to IR. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) is caused by mutations in the phenylalanine hydroxylase (PAH) gene and is characterized by altered amino acid metabolism. More than 1500 known PAH variants intricately determine a spectrum of metabolic phenotypes. We aim to report on clinical presentation and PAH variants identified in 23 hyperphenylalaninemia (HPA)/PKU Romanian patients. Our cohort exhibited classic PKU (73.9%, 17/23), mild PKU (17.4%, 4/23), and mild HPA (8.7%, 2/23). Severe central nervous system sequelae are frequent in our cohort in late-diagnosis symptomatic patients, which highlights yet again the significance of an early dietary treatment, neonatal screening and diagnosis, and facilitated access to treatment. Next-generation sequencing (NGS) identified a total of 11 PAH pathogenic variants, all previously reported, mostly missense changes (7/11) in important catalytic domains. c.1222C>T p.Arg408Trp was the most frequent variant, with an allele frequency of 56.5%. Twelve distinct genotypes were identified, the most frequent of which was p.Arg408Trp/p.Arg408Trp (34.8%, 8/23). Compound heterozygous genotypes were common (13/23), three of which had not been previously reported to the best of our knowledge; two correlated with cPKU and one showed an mPKU phenotype. Generally, there are genotype–phenotype correlation overlaps with the public data reported in BIOPKUdb; as our study shows, clinical correlates are subject to variation, in part due to uncontrolled or unknown epigenetic or environmental regulatory factors. We highlight the importance of establishing the genotype on top of using blood phenylalanine levels. [ABSTRACT FROM AUTHOR]

Introduction: Pompe disease is a rare, lysosomal disorder, characterized by intra-lysosomal glycogen accumulation due to an impaired function of α-glucosidase enzyme. The laboratory testing for Pompe is usually performed by enzyme activity, genetic test, or urine glucose tetrasaccharide (Glc4) screening by HPLC. Despite being a good preliminary marker, the Glc4 is not specific for Pompe. Objective: The purpose of the present study was to develop a simple methodology using liquid chromatography-high resolution mass spectrometry (LC-HRMS) for targeted quantitative analysis of Glc4 combined with untargeted metabolic profiling in a single analytical run to search for complementary biomarkers in Pompe disease. Methods: We collected 21 urine specimens from 13 Pompe disease patients and compared their metabolic signatures with 21 control specimens. Results: Multivariate statistical analyses on the untargeted profiling data revealed Glc4, creatine, sorbitol/mannitol, L-phenylalanine, N-acetyl-4-aminobutanal, N-acetyl-L-aspartic acid, and 2-aminobenzoic acid as significantly altered in Pompe disease. This panel of metabolites increased sample class prediction (Pompe disease versus control) compared with a single biomarker. Conclusion: This study has demonstrated the potential of combined acquisition methods in LC-HRMS for Pompe disease investigation, allowing for routine determination of an established biomarker and discovery of complementary candidate biomarkers that may increase diagnostic accuracy, or improve the risk stratification of patients with disparate clinical phenotypes. [ABSTRACT FROM AUTHOR]

Objective: Through a literature review, make recommendations regarding immunizations in people living with Inborn Error of Metabolism (IEM) in Brazil, assess the possible impact on metabolic decompensations after immunization, and if this specific population may have an impaired immune response to vaccines. Source of data: The MeSH Terms vaccination OR vaccine OR immunization associated with the term inborn error of metabolism AND recommendation were used in combination with search databases. Only articles published after 1990, in the languages English, Spanish, French or Portuguese, human-related were included. Synthesis of data: A total of 44 articles were included to make the following recommendations. Individuals with IEMs need to be up to date with their immunizations. Regarding which vaccines should be offered, children and adults should follow the routine immunization schedules locally available, including the COVID-19 vaccines. The only exception is the rotavirus vaccine for hereditary fructose intolerance. The benefit of immunization outweighs the very low risk of metabolic decompensation. Since not all patients will have an adequate immune response, measuring antibody conversion and titers is recommended Conclusions: All patients should receive age-appropriate immunizations in their respective schedules without delays. The only situation when vaccination may be contraindicated is with oral rotavirus vaccine in hereditary fructose intolerance. Monitoring the levels of antibodies should be done to detect any immune dysfunction or the necessity for boosters. A personalized immunization schedule is ideal for patients with IEMs. The reference organizations could improve their recommendations to address all IEMs, not only some of them. [ABSTRACT FROM AUTHOR]

Isovaleric aciduria (IVA) is a rare disorder of leucine metabolism and part of newborn screening (NBS) programs worldwide. However, NBS for IVA is hampered by, first, the increased birth prevalence due to the identification of individuals with an attenuated disease variant (so-called "mild" IVA) and, second, an increasing number of false positive screening results due to the use of pivmecillinam contained in the medication. Recently, machine learning (ML) methods have been analyzed, analogous to new biomarkers or second-tier methods, in the context of NBS. In this study, we investigated the application of machine learning classification methods to improve IVA classification using an NBS data set containing 2,106,090 newborns screened in Heidelberg, Germany. Therefore, we propose to combine two methods, linear discriminant analysis, and ridge logistic regression as an additional step, a digital-tier, to traditional NBS. Our results show that this reduces the false positive rate by 69.9 % from 103 to 31 while maintaining 100 % sensitivity in cross-validation. The ML methods were able to classify mild and classic IVA from normal newborns solely based on the NBS data and revealed that besides isovalerylcarnitine (C5), the metabolite concentration of tryptophan (Trp) is important for improved classification. Overall, applying ML methods to improve the specificity of IVA could have a major impact on newborns, as it could reduce the newborns' and families' burden of false positives or over-treatment. [ABSTRACT FROM AUTHOR]

Abstract We present the results of our experience in the diagnosis of inborn errors of metabolism (IEM) since the Expanded Newborn Screening was implemented in our Region. Dried blood samples were collected 48 h after birth. Amino acids and acylcarnitines were quantitated by mass spectrometry (MS)/MS. Newborns with alterations were referred to the clinical centers for follow‐up. Biochemical and molecular genetic studies for confirmation of a disease were performed. In the period 2011 to 2019, 592 822 children were screened: 902 of them were referred for abnormal results. An IEM was confirmed in 222 (1/2670): aminoacidopathies: 89 hyperphenylalaninemia (HPA) (51 benign HPA, 32 phenylketonuria, 4 DNAJC12 defect, and 2 primapterinuria), 6 hypermethioninemia, 3 tyrosinemia type 1 (TYR‐1), 1 TYR‐3, 4 maple syrup urine disease (MSUD), 2 branched‐chain amino acid transferase 2 deficiency, 2 homocystinuria, 1 cystinuria, 2 ornithine transcarbamylase (OTC) deficiency, 2 citrullinemia type I (CTLN1); FAO defects: 43 medium‐chain acyl‐CoA dehydrogenase deficiency (MCADD), 13 very long‐chain acyl‐CoA dehydrogenase deficiency, 2 long‐chain 3‐hydroxyacyl‐CoA dehydrogenase deficiency (LCHADD), 1 multiple acyl‐coA dehydrogenation deficiency, 11 systemic primary carnitine deficiency, 2 carnitine palmitoyltransferase type 2 (CPT‐II) deficiency, 1 CPT‐I deficiency; organic acidurias: 12 glutaric aciduria type 1 (GA‐1), 4 methylmalonic acidemia (MMA), 7 MMA including combined cases with homocystinuria (MMAHC), 6 propionic acidemia (PA), 7 3‐methylcrotonyl‐CoA carboxylase, 1 3‐hydroxy‐3‐methylglutaryl‐CoA lyase deficiency lyase deficiency. Only 19 infants (8.5%) were symptomatic at newborn screening result (1 LCHADD, 5 PA, 1 CPT‐II deficiency, 1 MMA, 3 MMAHC, 2 MSUD, 2 OTC deficiency, 1 CTLN1, 1 MCADD, 2 TYR‐1). No false negative cases were identified. Genetic diagnosis was conclusive in all biochemically confirmed cases, except for two infants with HPA, identifying pathogenic variants in 32 different genes. The conditions with the highest incidence were HPA (1/6661) and MCAD deficiencies (1/13 787).

Objective: Through a literature review, make recommendations regarding immunizations in people living with Inborn Error of Metabolism (IEM) in Brazil, assess the possible impact on metabolic decompensations after immunization, and if this specific population may have an impaired immune response to vaccines. Source of data: The MeSH Terms vaccination OR vaccine OR immunization associated with the term inborn error of metabolism AND recommendation were used in combination with search databases. Only articles published after 1990, in the languages English, Spanish, French or Portuguese, human-related were included. Synthesis of data: A total of 44 articles were included to make the following recommendations. Individuals with IEMs need to be up to date with their immunizations. Regarding which vaccines should be offered, children and adults should follow the routine immunization schedules locally available, including the COVID-19 vaccines. The only exception is the rotavirus vaccine for hereditary fructose intolerance. The benefit of immunization outweighs the very low risk of metabolic decompensation. Since not all patients will have an adequate immune response, measuring antibody conversion and titers is recommended Conclusions: All patients should receive age-appropriate immunizations in their respective schedules without delays. The only situation when vaccination may be contraindicated is with oral rotavirus vaccine in hereditary fructose intolerance. Monitoring the levels of antibodies should be done to detect any immune dysfunction or the necessity for boosters. A personalized immunization schedule is ideal for patients with IEMs. The reference organizations could improve their recommendations to address all IEMs, not only some of them.

Iodine is an essential mineral required for the synthesis of thyroid hormones. Iodine plays a critical role in growth and neurocognitive development. Classical galactosaemia is a disorder resulting from an inborn error in galactose metabolism. Its current management consists of life-long lactose and galactose dietary restriction. This study estimated dietary intakes of iodine in infants and children with classical galactosaemia in the Republic of Ireland. The diets of 43 participants (aged 7 months–18 years) with classical galactosaemia were assessed for iodine intake using an iodine-specific food frequency questionnaire. Intakes were compared to the European Food Safety Authority (EFSA) dietary recommendations for iodine intake. The potential role of iodine fortification of dairy alternative products was also examined. There were no significant differences observed between sex, ethnicity and parental education and meeting dietary iodine recommendations. Differences, however, were seen between age groups, causing the p value to approach statistical significance (p = 0.06). Infants consuming infant formula were likely to meet iodine recommendations. However, over half (53%) of children aged 1–18 years had average intakes below the recommendations for age. For these children, consumption of iodine-fortified dairy alternative milk was the leading source of iodine in the diets, followed by fish/shellfish and eggs. An assessment of iodine intake should be undertaken during dietetic reviews for those with classical galactosaemia. Mandatory iodine fortification of all dairy alternative products would result in 92% of the total population cohort meeting iodine recommendations based on their current consumption. [ABSTRACT FROM AUTHOR]

Asparagine Synthetase Deficiency (ASNSD) is a disease caused by mutations in asparagine synthetase (ASNS). Newborns exhibit microcephaly, intractable epileptic-like seizures, progressive brain atrophy, and axial hypotonia. ASNSD results in global developmental delays and premature death. The present report describes a 9-year-old child who is a compound heterozygote with ASNS mutations c.1439C > T and c.239A > G leading to variants p.S480F and p.N80S, respectively. When grown in a complete culture medium, primary fibroblasts from the child contained ASNS mRNA and protein levels similar to an unrelated wild-type fibroblast cell line. When the child's fibroblasts were cultured for up to 72 h in a medium lacking asparagine, proliferation was reduced by about 50%. Purification of ASNS proteins harboring either the S480F or the N80S substitution had reduced enzymatic activity by 80% and 50%, respectively. Ectopic expression of either variant in ASNS-null Jensen rat sarcoma (JRS) cells did not support proliferation in the absence of medium-supplied asparagine, whereas expression of wild-type enzyme completely restored growth. These studies add to the list of pathogenic ASNS variants and use enzyme activity and protein expression in ASNS-null cells to expand our knowledge of the biological impact of mutations in the ASNS gene. [ABSTRACT FROM AUTHOR]

Background: Arginase 1 Deficiency (ARG1-D) is a rare autosomal recessive urea cycle disorder (UCD) characterized by pathologic elevation of plasma arginine and debilitating manifestations. Based on clinical commonalities and low disease awareness, ARG1-D can be diagnosed as hereditary spastic paraplegia (HSP), leading to treatment delays. Cases: A Hispanic woman with unremarkable medical history experienced progressive lower-limb spasticity in her 20s and received a diagnosis of HSP. She developed significant gait abnormalities and is unable to walk without assistance. More recently, two Hispanic brothers with childhood-onset manifestations including lowerlimb spasticity, developmental delays, and seizures presented with suspected HSP. All three patients were ultimately diagnosed with ARG1-D based on plasma arginine several-fold above normal levels and loss-offunction ARG1 variants. Disease progression occurred before ARG1-D was correctly diagnosed. Literature Review: Retrospective analyses demonstrate that diagnostic delays in ARG1-D are common and can be lengthy. Because of clinical similarities between ARG1-D and HSP, such as insidious onset and progressive spasticity, accurate diagnosis of ARG1-D is challenging. Timely ARG1-D diagnosis is critical because this UCD is a treatable genetic cause of progressive lower-limb spasticity. Conclusions: Arginase 1 Deficiency should be considered in HSP differential diagnosis until biochemically/genetically excluded, and should be routinely included in HSP gene panels. [ABSTRACT FROM AUTHOR]