Clinical and genetic analysis of methylmalonic aciduria in 60 patients from Southern China: a single center retrospective study.

BACKGROUND: Methylmalonic aciduria (MMA) is a group of rare genetic metabolic disorders resulting from defects in methylmalonyl coenzyme A mutase (MCM) or intracellular cobalamin (cbl) metabolism. MMA patients show diverse clinical and genetic features across different subtypes and populations. METHODS: We retrospectively recruited 60 MMA patients from a single center and diagnosed them based on their clinical manifestations and biochemical assays. We then performed genetic analysis to confirm the diagnosis and identify the causal variants. RESULTS: We confirmed the common clinical manifestations of MMA reported previously. We also described four rare MMA cases with unusual symptoms or genetic variants, such as pulmonary hypertension or limb weakness in late-onset patients. We identified 15 MMACHC and 26 MMUT variants in 57 patients, including 6 novel MMUT variants. Two patients had only one MMAA variant each, and one patient had mild MMA due to mitochondrial DNA depletion syndrome caused by a SUCLA2 variant. Among 12 critically ill patients, isolated MMA was associated with higher C3, blood ammonia, and acidosis, while combined MMA was linked to hydrocephalus on skull MRI. MMACHC c.658-660delAAG and MMUT c.1280G > A variants were correlated with more severe phenotypes. CONCLUSIONS: Our study demonstrates the clinical and genotypic heterogeneity of MMA patients and indicates that metabolic screening and genetic analysis are useful tools to identify rare cases.

Evaluation of the first 5 years of a glutaric aciduria type I neonatal screening programme in Asturias.

INTRODUCTION: . Neonatal screening of glutaric aciduria type 1 (GA-1) has brought radical changes in the course and outcomes of this disease. This study analyses the outcomes of the first 5 years (2015-2019) of the AGA1 neonatal screening programme in our autonomous community. MATERIAL: . We conducted an observational, descriptive and retrospective study. All neonates born between January 1, 2015 and December 31, 2019 that participated in the neonatal screening programme were included in the study. The glutarylcarnitine (C5DC) concentration in dry blood spot samples was measured by means of tandem mass spectrometry applying a cut-off point of 0.25 µmol/L. RESULTS: . A total of 30 120 newborns underwent screening. We found differences in the C5DC concentration based on gestational age, type of feeding and hours of life at sample collection. These differences were not relevant for screening purposes. There were no differences between neonates with weights smaller and greater than 1500 g. Screening identified 2 affected patients and there were 3 false positives. There were no false negatives. The diagnosis was confirmed by genetic testing. Patients have been in treatment since diagnosis and have not developed encephalopathic crises in the first 4 years of life. CONCLUSIONS: . Screening allowed early diagnosis of two cases of GA-1 in the first 5 years since its introduction in our autonomous community. Although there were differences in C5DC levels based on gestational age, type of feeding and hours of life at blood extraction, they were not relevant for screening.

Characterizing the mechanism of action for mRNA therapeutics for the treatment of propionic acidemia, methylmalonic acidemia, and phenylketonuria.

Messenger RNA (mRNA) therapeutics delivered via lipid nanoparticles hold the potential to treat metabolic diseases caused by protein deficiency, including propionic acidemia (PA), methylmalonic acidemia (MMA), and phenylketonuria (PKU). Herein we report results from multiple independent preclinical studies of mRNA-3927 (an investigational treatment for PA), mRNA-3705 (an investigational treatment for MMA), and mRNA-3210 (an investigational treatment for PKU) in murine models of each disease. All 3 mRNA therapeutics exhibited pharmacokinetic/pharmacodynamic (PK/PD) responses in their respective murine model by driving mRNA, protein, and/or protein activity responses, as well as by decreasing levels of the relevant biomarker(s) when compared to control-treated animals. These preclinical data were then used to develop translational PK/PD models, which were scaled allometrically to humans to predict starting doses for first-in-human clinical studies for each disease. The predicted first-in-human doses for mRNA-3927, mRNA-3705, and mRNA-3210 were determined to be 0.3, 0.1, and 0.4 mg/kg, respectively.

[Newborn screening in France: news and perspectives]. / Le dépistage néonatal en France : actualités et perspectives.

Newborn screening is a major public health concern. In France, it was established in 1972 with systematic screening for phenylketonuria. Subsequently, other screenings, including congenital hypothyroidism, congenital adrenal hyperplasia, cystic fibrosis, and sickle cell disease, were added. The introduction of tandem mass spectrometry in screening laboratories in 2020 enabled the inclusion of eight additional inherited metabolic diseases: aminoacidopathies (tyrosinemia type I, maple syrup urine disease, and homocystinuria), organic acidurias (isovaleric and glutaric type I acidurias), and disorders of fatty acid metabolism (MCADD, long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD), and primary carnitine deficiency). We briefly present these newly added diseases, of which public awareness is still incomplete.

Gene replacement therapies for inherited disorders of neurotransmission: Current progress in succinic semialdehyde dehydrogenase deficiency.

Neurodevelopment is a highly organized and complex process involving lasting and often irreversible changes in the central nervous system. Inherited disorders of neurotransmission (IDNT) are a group of genetic disorders where neurotransmission is primarily affected, resulting in abnormal brain development from early life, manifest as neurodevelopmental disorders and other chronic conditions. In principle, IDNT (particularly those of monogenic causes) are amenable to gene replacement therapy via precise genetic correction. However, practical challenges for gene replacement therapy remain major hurdles for its translation from bench to bedside. We discuss key considerations for the development of gene replacement therapies for IDNT. As an example, we describe our ongoing work on gene replacement therapy for succinic semialdehyde dehydrogenase deficiency, a GABA catabolic disorder.

Abnormal biochemical indicators of neonatal inherited metabolic disease in carriers.

BACKGROUND: Traditional biochemical screening for neonatal inherited metabolic diseases has high false-positive rates and low positive predictive values, which are not conducive to early diagnosis and increase parents' anxiety. This study analysed the relationship between gene variant carriers and their biochemical indicators in traditional biochemical screening, aiming to find explanations for false positives in newborns. RESULTS: This retrospective study included 962 newborns. Newborns underwent traditional biochemical screening at birth using blood staining and genomic sequencing of their stored blood staining using the NeoSeq Pro panel, which was able to detect 154 pathogenic genes and 86 diseases. A total of 632 newborns were carriers of gene variants. 56% of congenital hypothyroidism carriers had higher thyroid-stimulating hormone levels than normal newborns. Abnormal biochemical indices were detected in 71% of carriers of organic acid metabolic diseases, 69% of carriers of amino acid metabolic diseases, and 85% of carriers of fatty acid ß oxidation disorders. In carriers associated with organic acid metabolic diseases, the propionylcarnitine (C3), C3/acetylcarnitine (C2), and methylmalonylcarnitine (C4DC) + 3-hydroxyisovalerylcarnitine (C5OH) levels were higher than those in non-carriers (C3: 4.12 vs. 1.66 µmol/L; C3/C2: 0.15 vs. 0.09; C4DC + C5OH: 0.22 vs. 0.19 µmol/L). In carriers associated with amino acid metabolic diseases, phenylalanine levels were higher than those in non-carriers (68.00 vs. 52.05 µmol/L). For carriers of fatty acid ß oxidation disorders, butyrylcarnitine levels were higher than those in non-carriers (0.31 vs. 0.21 µmol/L), while the free carnitine levels were lower than those in non-carriers (14.65 vs. 21.87 µmol/L). There was a higher occurrence of carriers among newborns who received false-positive results for amino acid metabolic diseases compared to those who received negative results (15.52% vs. 6.71%). Similarly, there was a higher occurrence of carriers among newborns who received false-positive results for fatty acid ß oxidation disorders compared to those who received negative results (28.30% vs. 7.29%). CONCLUSIONS: This study showed that the carriers comprised a large number of newborns. Carriers had abnormal biochemical indicators compared with non-carriers, which could explain the false-positive rate for newborns using traditional newborn biochemical screening, especially in amino acid metabolic and fatty acid ß oxidation disorders.

Clinical and molecular outcomes from the 5-Year natural history study of SSADH Deficiency, a model metabolic neurodevelopmental disorder.

BACKGROUND: Succinic semialdehyde dehydrogenase deficiency (SSADHD) represents a model neurometabolic disease at the fulcrum of translational research within the Boston Children's Hospital Intellectual and Developmental Disabilities Research Centers (IDDRC), including the NIH-sponsored natural history study of clinical, neurophysiological, neuroimaging, and molecular markers, patient-derived induced pluripotent stem cells (iPSC) characterization, and development of a murine model for tightly regulated, cell-specific gene therapy. METHODS: SSADHD subjects underwent clinical evaluations, neuropsychological assessments, biochemical quantification of γ-aminobutyrate (GABA) and related metabolites, electroencephalography (standard and high density), magnetoencephalography, transcranial magnetic stimulation, magnetic resonance imaging and spectroscopy, and genetic tests. This was parallel to laboratory molecular investigations of in vitro GABAergic neurons derived from induced human pluripotent stem cells (hiPSCs) of SSADHD subjects and biochemical analyses performed on a versatile murine model that uses an inducible and reversible rescue strategy allowing on-demand and cell-specific gene therapy. RESULTS: The 62 SSADHD subjects [53% females, median (IQR) age of 9.6 (5.4-14.5) years] included in the study had a reported symptom onset at ∼ 6 months and were diagnosed at a median age of 4 years. Language developmental delays were more prominent than motor. Autism, epilepsy, movement disorders, sleep disturbances, and various psychiatric behaviors constituted the core of the disorder's clinical phenotype. Lower clinical severity scores, indicating worst severity, coincided with older age (R= -0.302, p = 0.03), as well as age-adjusted lower values of plasma γ-aminobutyrate (GABA) (R = 0.337, p = 0.02) and γ-hydroxybutyrate (GHB) (R = 0.360, p = 0.05). While epilepsy and psychiatric behaviors increase in severity with age, communication abilities and motor function tend to improve. iPSCs, which were differentiated into GABAergic neurons, represent the first in vitro neuronal model of SSADHD and express the neuronal marker microtubule-associated protein 2 (MAP2), as well as GABA. GABA-metabolism in induced GABAergic neurons could be reversed using CRISPR correction of the pathogenic variants or mRNA transfection and SSADHD iPSCs were associated with excessive glutamatergic activity and related synaptic excitation. CONCLUSIONS: Findings from the SSADHD Natural History Study converge with iPSC and animal model work focused on a common disorder within our IDDRC, deepening our knowledge of the pathophysiology and longitudinal clinical course of a complex neurodevelopmental disorder. This further enables the identification of biomarkers and changes throughout development that will be essential for upcoming targeted trials of enzyme replacement and gene therapy.

Dual rare genetic diseases in five pediatric patients: insights from next-generation diagnostic methods.

BACKGROUND: Clinicians traditionally aim to identify a singular explanation for the clinical presentation of a patient; however, in some cases, the diagnosis may remain elusive or fail to comprehensively explain the clinical findings. In recent years, advancements in next-generation sequencing, including whole-exome sequencing, have led to the incidental identification of dual diagnoses in patients. Herein we present the cases of five pediatric patients diagnosed with dual rare genetic diseases. Their natural history and diagnostic process were explored, and lessons learned from utilizing next-generation diagnostic technologies have been reported. RESULTS: Five pediatric cases (3 boys, 2 girls) with dual diagnoses were reported. The age at diagnosis was from 3 months to 10 years. The main clinical presentations were psychomotor retardation and increased muscular tension, some accompanied with liver dysfunction, abnormal appearance, precocious puberty, dorsiflexion restriction and varus of both feet, etc. After whole-exome sequencing, nine diseases were confirmed in these patients: Angelman syndrome and Krabbe disease in case 1, Citrin deficiency and Kabuki syndrome in case 2, Homocysteinemia type 2 and Copy number variant in case 3, Isolated methylmalonic acidemia and Niemann-Pick disease type B in case 4, Isolated methylmalonic acidemia and 21-hydroxylase deficiency in case 5. Fifteen gene mutations and 2 CNVs were identified. Four novel mutations were observed, including c.15292de1A in KMT2D, c.159_164inv and c.1427G > A in SLC25A13, and c.591 C > G in MTHFR. CONCLUSIONS: Our findings underscore the importance of clinicians being vigilant about the significance of historical and physical examination. Comprehensive clinical experience is crucial for identifying atypical clinical features, particularly in cases involving dual rare genetic diseases.

[Clinical analysis and genetic diagnosis of three children with Isoleucine metabolic disorders due to variants of HSD17B10 and ACAT1 genes].

OBJECTIVE: To explore the clinical, biochemical and genetic characteristics of three children with Isoleucine metabolic disorders due to variants of HSD17B10 and ACAT1 genes. METHODS: Two children with 17ß hydroxysteroid dehydrogenase 10 (HSD17B10) deficiency and a child with ß-ketothiolase deficiency (BKD) diagnosed at Shanghai Children's Hospital between 2014 and 2021 were selected as the study subjects. Clinical data of the children were collected. The children were subjected to blood acylcarnitine, urinary organic acid and genetic testing, and candidate variants were analyzed with bioinformatic tools. RESULTS: The main symptoms of the three children had included epilepsy, developmental delay, hypotonia and acidosis. Their blood acylcarnitine methylcrotonyl carnitine (C5:1), 3-hydroxyisovalerylcarnitine (C5-OH) and 3-hydroxybutylcarnitine (C4OH) were increased to various extents, and urine organic acids including methyl crotonylglycine and 2-methyl-3-hydroxybutyric acid were significantly increased. Child 1 and child 2 were respectively found to harbor a c.347G>A (p.R116Q) variant and a c.274G>A (p.A92T) variant of the HSD17B10 gene, and child 3 was found to harbor compound heterozygous variants of the ACAT1 gene, namely c.547G>A (p.G183R) and a c.331G>C (p.A111P). Among these, the c.274G>A (p.A92T) and c.331G>C (p.A111P) variants were unreported previously. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), they were respectively classified as variant of unknown significance (PP3_Strong+PM2_supporting) and likely pathogenic (PM3+PM2_Supporting+PP3_Moderate+PP4). CONCLUSION: Both the HSD17B10 deficiency and BKD can lead to Isoleucine metabolism disorders, which may be difficult to distinguish clinically. Genetic testing can further confirm the diagnosis. Discoveries of the HSD17B10: c.274G>A (p.A92T) variant and the ACAT1: c.331G>C (p.A111P) variant have enriched the mutational spectrum of the two diseases.

New data supporting that early diagnosis and treatment are possible and necessary in intracellular cobalamin depletion: the case of transcobalamin II deficiency.

OBJECTIVES: Transcobalamin II (TC) promotes the cellular uptake of cobalamin (Cbl) through receptor-mediated endocytosis of the TC-cbl complex in peripheral tissues. TC deficiency is a rare disorder that causes intracellular Cbl depletion. It presents in early infancy with a failure to thrive, diarrhea, anemia, agammaglobulinemia, and pancytopenia. Data from five TC-deficient patients including clinical, biochemical, and molecular findings, as well as long-term outcomes, were collected. CASE PRESENTATION: Mutation analysis revealed one unreported pathogenic variant in the TCN2 gene. One patient had exocrine pancreatic insufficiency. We conducted a retrospective analysis of C3 and C3/C2 from dried blood samples, as this is implemented for newborn screening (NBS). We detected a marked increase in the C3/C2 ratio in two samples. Treatment was based on parenteral Cbl. Three patients treated before six months of age had an initial favorable outcome, whereas the two treated later or inadequately had neurological impairment. CONCLUSIONS: This is the first report of Argentinean patients with TC deficiency that detected a new variant in TCN2. NBS may be a tool for the early detection of TC deficiency. This data emphasizes that TC deficiency is a severe disorder that requires early detection and long-term, aggressive therapy. Accurate diagnosis is imperative, because early detection and treatment can be life-saving.

The continuously evolving phenotype of succinic semialdehyde dehydrogenase deficiency.

The objective of the study is to evaluate the evolving phenotype and genetic spectrum of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD) in long-term follow-up. Longitudinal clinical and biochemical data of 22 pediatric and 9 adult individuals with SSADHD from the patient registry of the International Working Group on Neurotransmitter related Disorders (iNTD) were studied with in silico analyses, pathogenicity scores and molecular modeling of ALDH5A1 variants. Leading initial symptoms, with onset in infancy, were developmental delay and hypotonia. Year of birth and specific initial symptoms influenced the diagnostic delay. Clinical phenotype of 26 individuals (median 12 years, range 1.8-33.4 years) showed a diversifying course in follow-up: 77% behavioral problems, 76% coordination problems, 73% speech disorders, 58% epileptic seizures and 40% movement disorders. After ataxia, dystonia (19%), chorea (11%) and hypokinesia (15%) were the most frequent movement disorders. Involvement of the dentate nucleus in brain imaging was observed together with movement disorders or coordination problems. Short attention span (78.6%) and distractibility (71.4%) were the most frequently behavior traits mentioned by parents while impulsiveness, problems communicating wishes or needs and compulsive behavior were addressed as strongly interfering with family life. Treatment was mainly aimed to control epileptic seizures and psychiatric symptoms. Four new pathogenic variants were identified. In silico scoring system, protein activity and pathogenicity score revealed a high correlation. A genotype/phenotype correlation was not observed, even in siblings. This study presents the diversifying characteristics of disease phenotype during the disease course, highlighting movement disorders, widens the knowledge on the genotypic spectrum of SSADHD and emphasizes a reliable application of in silico approaches.

Delays in latencies of median-nerve evoked magnetic fields in patients with succinic semialdehyde dehydrogenase deficiency.

OBJECTIVE: Succinic semialdehyde dehydrogenase deficiency (SSADHD) is a genetic disorder resulting in abnormal regulation of γ-aminobutyric acid, lipid metabolism, and myelin biogenesis, leading to ataxia, seizures, and cognitive impairment. Since the myelin sheath is thinner in a murine model of SSADHD compared to a wild type, we hypothesized that this also holds for human brain. We tested whether the conduction velocity in the somatosensory pathway is accordingly delayed. METHODS: Somatosensory evoked magnetic fields (SEF) produced by transcutaneous electrical stimulation of the median nerve were measured in 13 SSADHD patients, 11 healthy and 14 disease controls with focal epilepsy. The peak latencies of the initial four components (M1, M2, M3 and M4) were measured. RESULTS: The SEF waveforms and scalp topographies were comparable across the groups. The latencies were statistically significantly longer in the SSADHD group compared to the two controls. We found these latencies for the SSADHD, healthy and disease controls respectively to be: M1: (21.9 ± 0.8 ms [mean ± standard error of the mean], 20.4 ± 0.6 ms, and 21.0 ± 0.4 ms) (p < 0.05); M2: (36.1 ± 1.0 ms, 33.1 ± 0.6 ms, and 32.1 ± 1.1 ms) (p < 0.005); M3: (62.5 ± 2.4 ms, 54.7 ± 2.0 ms, and 49.9 ± 1.8 ms) (p < 0.005); M4: (86.2 ± 2.3 ms, 78.8 ± 2.8 ms, and 73.5 ± 2.9 ms) (p < 0.005). CONCLUSIONS: The SEF latencies are delayed in patients with SSADHD compared with healthy controls and disease controls. SIGNIFICANCE: This is the first study that compares conduction velocities in the somatosensory pathway in SSADHD, an inherited disorder of GABA metabolism. The longer peak latency implying slower conduction velocity supports the hypothesis that myelin sheath thickness is decreased in SSADHD.

Living-donor liver transplantation for methylmalonic acidemia patient with hepatocellular carcinoma: A case report and literature review.

BACKGROUND: Methylmalonic acidemia (MMA) is an autosomal recessive disorder caused by defects in propionyl-CoA (P-CoA) catabolism; of note, liver neoplasms rarely occur as a long-term complication of the disorder. Herein, we report the case of a patient with MMA and hepatocellular carcinoma (HCC) who was successfully treated with a living-donor liver transplant (LDLT) following prior kidney transplantation. CASE REPORT: A 25-year-old male patient with MMA underwent LDLT with a left lobe graft because of metabolic instability and liver neoplasms. He had presented with chronic symptoms of MMA, which had been diagnosed by genetic testing. Additionally, he had undergone living-donor kidney transplantation with his father as the donor due to end-stage kidney disease 6 years before the LDLT. He had an episode of metabolic decompensation triggered by coronavirus disease in 2019. Imaging studies revealed an intrahepatic neoplasm in the right hepatic lobe. Due to concerns about metabolic decompensation after hepatectomy, LDLT was performed using a left lobe graft obtained from the patient's mother. Pathological findings were consistent with the characteristics of well-to-moderately differentiated HCC. The postoperative course was uneventful, and the patient was discharged 48 days after the LDLT without any complications. At the 9-month follow-up, the patient's condition was satisfactory, with sufficient liver graft function and without metabolic decompensation. CONCLUSION: This case indicates that although HCC is a rare complication in patients with MMA, clinicians should be aware of hepatic malignancies during long-term follow-up.

[Clinical features and genetic analysis of three children with ß-ketothiolase deficiency].

OBJECTIVE: To explore the clinical features and genetic variants in three children suspected for ß-ketothiolase deficiency (BKTD). METHODS: Clinical manifestations, laboratory examination and genetic testing of three children suspected for BKTD at Henan Children's Hospital between January 2018 and October 2022 were collected, and their clinical and genetic variants were retrospectively analyzed. RESULTS: The children were all males with a age from 7 to 11 months. Their clinical manifestations have included poor spirit, shortness of breath, vomiting, convulsions after traumatic stress and/or infection. All of them had severe metabolic acidosis, elevated ketone bodies in blood and urine, hypoglycemia, with increased isoprenyl-carnitine and 3-hydroxyisovalyl-carnitine in the blood, and 2-methyl-3-hydroxybutyrate and methylprotaroyl glycine in the urine. All of them were found to harbor compound heterozygous variants of the ACAT1 gene, including c.1183G>T and a large fragment deletion (11q22.3-11q23.1) in child 1, c.121-3C>G and c.826+5_826+9delGTGTT in child 2, and c.928G>C and c.1142T>C in child 3. The variants harbored by children 2 and 3 were known to be pathogenic or likely pathogenic. The heterozygous c.1183G>T variant in child 1 was unreported previously and rated as a variant of unknown significance (PM2_Supporting+PP3+PP4) based on guidelines from the American College of Medical Genetics and Genomics. The large segment deletion in 11q22.3-11q23.1 has not been included in the DGV Database and was rated as a pathogenic copy number variation. CONCLUSION: The variants of the ACAT1 gene probably underlay the pathogenesis of BKTD in these three children.

ClinGen variant curation expert panel recommendations for classification of variants in GAMT, GATM and SLC6A8 for cerebral creatine deficiency syndromes.

Cerebral creatine deficiency syndromes (CCDS) are inherited metabolic phenotypes of creatine synthesis and transport. There are two enzyme deficiencies, guanidinoacetate methyltransferase (GAMT), encoded by GAMT and arginine-glycine amidinotransferase (AGAT), encoded by GATM, which are involved in the synthesis of creatine. After synthesis, creatine is taken up by a sodium-dependent membrane bound creatine transporter (CRTR), encoded by SLC6A8, into all organs. Creatine uptake is very important especially in high energy demanding organs such as the brain, and muscle. To classify the pathogenicity of variants in GAMT, GATM, and SLC6A8, we developed the CCDS Variant Curation Expert Panel (VCEP) in 2018, supported by The Clinical Genome Resource (ClinGen), a National Institutes of Health (NIH)-funded resource. We developed disease-specific variant classification guidelines for GAMT-, GATM-, and SLC6A8-related CCDS, adapted from the American College of Medical Genetics/Association of Molecular Pathology (ACMG/AMP) variant interpretation guidelines. We applied specific variant classification guidelines to 30 pilot variants in each of the three genes that have variants associated with CCDS. Our CCDS VCEP was approved by the ClinGen Sequence Variant Interpretation Working Group (SVI WG) and Clinical Domain Oversight Committee in July 2022. We curated 181 variants including 72 variants in GAMT, 45 variants in GATM, and 64 variants in SLC6A8 and submitted these classifications to ClinVar, a public variant database supported by the National Center for Biotechnology Information. Missense variants were the most common variant type in all three genes. We submitted 32 new variants and reclassified 34 variants with conflicting interpretations. We report specific phenotype (PP4) using a points system based on the urine and plasma guanidinoacetate and creatine levels, brain magnetic resonance spectroscopy (MRS) creatine level, and enzyme activity or creatine uptake in fibroblasts ranging from PP4, PP4_Moderate and PP4_Strong. Our CCDS VCEP is one of the first panels applying disease specific variant classification algorithms for an X-linked disease. The availability of these guidelines and classifications can guide molecular genetics and genomic laboratories and health care providers to assess the molecular diagnosis of individuals with a CCDS phenotype.

Consensus guidelines for the diagnosis and management of succinic semialdehyde dehydrogenase deficiency.

Succinic semialdehyde dehydrogenase deficiency (SSADHD) (OMIM #271980) is a rare autosomal recessive metabolic disorder caused by pathogenic variants of ALDH5A1. Deficiency of SSADH results in accumulation of γ-aminobutyric acid (GABA) and other GABA-related metabolites. The clinical phenotype of SSADHD includes a broad spectrum of non-pathognomonic symptoms such as cognitive disabilities, communication and language deficits, movement disorders, epilepsy, sleep disturbances, attention problems, anxiety, and obsessive-compulsive traits. Current treatment options for SSADHD remain supportive, but there are ongoing attempts to develop targeted genetic therapies. This study aimed to create consensus guidelines for the diagnosis and management of SSADHD. Thirty relevant statements were initially addressed by a systematic literature review, resulting in different evidence levels of strength according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. The highest level of evidence (level A), based on randomized controlled trials, was unavailable for any of the statements. Based on cohort studies, Level B evidence was available for 12 (40%) of the statements. Thereupon, through a process following the Delphi Method and directed by the Appraisal of Guidelines for Research and Evaluation (AGREE II) criteria, expert opinion was sought, and members of an SSADHD Consensus Group evaluated all the statements. The group consisted of neurologists, epileptologists, neuropsychologists, neurophysiologists, metabolic disease specialists, clinical and biochemical geneticists, and laboratory scientists affiliated with 19 institutions from 11 countries who have clinical experience with SSADHD patients and have studied the disorder. Representatives from parent groups were also included in the Consensus Group. An analysis of the survey's results yielded 25 (83%) strong and 5 (17%) weak agreement strengths. These first-of-their-kind consensus guidelines intend to consolidate and unify the optimal care that can be provided to individuals with SSADHD.

[Clinical and genetic spectrum of 6 cases with asparagine synthetase deficiency].

Objective: To explore the clinical and genetic characteristics of asparagine synthase deficiency. Methods: Case series studies. Retrospective analysis and summary of the clinical data of 6 cases with asparagine synthase deficiency who were diagnosed by genetic testing and admitted to the Third Affiliated Hospital of Zhengzhou University from May 2017 to April 2023 were analyzed retrospectively. The main clinical features, laboratory and imaging examination characteristics of the 6 cases were summarized, and the gene variation sites of them were analyzed. Results: All of the 6 cases were male, with onset ages ranging from 1 month to 1 year and 4 months. All of the 6 cases had cognitive and motor developmental delay, with 3 cases starting with developmental delay, 3 cases starting with convulsions and later experiencing developmental arrest or even regression. All of 6 cases had epilepsy, in whom 2 cases with severe microcephaly developed epileptic encephalopathy in the early stages of infancy with spasms as the main form of convulsions, 4 cases with mild or no microcephaly gradually evolved into convulsions with no fever after multiple febrile convulsions with focal seizures, tonic clonic seizures and tonic seizure as the main forms of convulsions. Three cases of 4 gradually developed into stagnation or even regression of development and ataxia after multiple convulsions with no fever. There were normal cranial imaging in 2 cases, dysplasia of the brains in 1 cases, frontal lobe apex accompanied by abnormal white matter signal in the frontal lobe and thin corpus callosum in 1 case, thin corpus callosum and abnormal lateral ventricular morphology in 1 case, and normal in early stage, but gradually developing into cerebellar atrophy at the age of 5 years and 9 months in 1 case. Two cases underwent visual evoked potential tests, the results of which were both abnormal. Three cases underwent auditory evoked potential examination, with 1 being normal and 2 being abnormal. All of 6 cases had variations in the asparagine synthase gene, with 2 deletion variations and 7 missense variations. The variations of 2 cases had not been reported so far, including c.1341_1343del and c.1283A>G, c.1165_1167del and c.1075G>A. The follow-up time ranged from 3 months to 53 months. Two cases who had severe microcephaly died in infancy, while the other 4 cases with mild or no microcephaly were in survival states until the follow-up days but the control of epilepsy was poor. Conclusions: Asparagine synthase deficiency has a certain degree of heterogeneity in clinical phenotype. Children with obvious microcephaly often present as severe cases, while children with mild or no microcephaly have relatively mild clinical manifestations. The variation of asparagine synthetase gene is mainly missense variation.

Comprehensive metabolomics analysis reveals novel biomarkers and pathways in falsely suspected glutaric aciduria Type-1 newborns.

BACKGROUND: Glutaric aciduria type-1 (GA-1) is a rare metabolic disorder due to glutaryl coenzyme A dehydrogenase deficiency, causing elevated levels of glutaryl-CoA and its derivatives. GA-1 exhibits symptoms like macrocephaly, developmental delays, and movement disorders. Timely diagnosis through genetic testing and newborn screening is crucial. However, in some cases, transiently elevated level of glutarylcarnitine (C5DC) challenges accurate diagnosis, highlighting the need for alternative diagnostic methods, like mass spectrometry-based untargeted metabolomics, to identify additional biomarkers for distinguishing falsely suspected GA-1 from healthy newborns. METHODOLOGY: DBS samples from falsely suspected GA-1 newborns (n = 47) and matched control were collected through the NBS program. Untargeted metabolomics using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) was performed to enable biomarker and pathway investigations for significantly altered metabolites. RESULTS: 582 and 546 were up- and down-regulated metabolites in transient GA-1. 155 endogenous metabolites displayed significant variations compared to the control group. Furthermore, our data identified novel altered metabolic biomarkers, such as N-palmitoylcysteine, heptacarboxyporphyrin, 3-hydroxylinoleoylcarnitine, and monoacylglyceride (MG) (0:0/20:1/0:0), along with perturbed metabolic pathways like sphingolipid and thiamine metabolism associated with the transient elevated C5DC levels in DBS samples. CONCLUSIONS: A distinct metabolic pattern linked to the transient C5DC elevation in newborns was reported to enhance the prediction of the falsely positive cases, which could help avoiding unnecessary medical treatments and minimizing the financial burdens in the health sector.

Identifying potential dietary treatments for inherited metabolic disorders using Drosophila nutrigenomics.

Inherited metabolic disorders are a group of genetic conditions that can cause severe neurological impairment and child mortality. Uniquely, these disorders respond to dietary treatment; however, this option remains largely unexplored because of low disorder prevalence and the lack of a suitable paradigm for testing diets. Here, we screened 35 Drosophila amino acid disorder models for disease-diet interactions and found 26 with diet-altered development and/or survival. Using a targeted multi-nutrient array, we examine the interaction in a model of isolated sulfite oxidase deficiency, an infant-lethal disorder. We show that dietary cysteine depletion normalizes their metabolic profile and rescues development, neurophysiology, behavior, and lifelong fly survival, thus providing a basis for further study into the pathogenic mechanisms involved in this disorder. Our work highlights the diet-sensitive nature of metabolic disorders and establishes Drosophila as a valuable tool for nutrigenomic studies for informing potential dietary therapies.

[Clinical and genetic analysis of two children with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency].

OBJECTIVE: To explore the clinical characteristics and genetic variants of two children with 3-hydroxy-3-methylglutaryl-coenzyme A lyase deficiency (HMGCLD). METHODS: Two children with HMGCLD diagnosed at Henan Provincial Children's Hospital respectively in December 2019 and June 2022 were selected as the study subjects. Clinical data and results of laboratory testing were analyzed retrospectively. RESULTS: Both children had manifested with repeated convulsions, severe hypoglycemia, metabolic acidosis and liver dysfunction. Blood amino acids and acylcarnitine analysis showed increased 3-hydroxy-isovalyl carnitine (C5OH) and 3-hydroxy-isovalyl carnitine/capryloyl carnitine ratio (C5OH/C8), and urinary organic acid analysis showed increased 3-hydroxyl-3-methyl glutaric acid, 3-methyl glutaric acid, 3-methyl glutaconic acid, 3-hydroxyisoglycine and 3-methylprotarylglycine. Child 1 was found to harbor homozygous c.722C>T variants of the HMGCL gene, which was rated as uncertain significance (PM2_Supporting+PP3). Child 2 was found to harbor homozygous c.121C>T variants of the HMGCL gene, which was rated as pathogenic variant (PVS1+PM2_Supporting+PP4). CONCLUSION: Acute episode of HMGCLD is usually characterized by metabolic disorders such as hypoglycemia and metabolic acidosis, and elevated organic acids in urine may facilitate the differential diagnosis, though definite diagnosis will rely on genetic testing.