[Newborn screening in France: news and 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.

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.

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 β 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 β 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 β 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 β oxidation disorders.

Newborn screening for aromatic l-amino acid decarboxylase deficiency - Strategies, results, and implication for prevalence calculations

BACKGROUND

Aromatic l-amino acid decarboxylase deficiency (AADCD) is a rare, autosomal-recessive neurometabolic disorder caused by variants in dopa decarboxylase (DDC) gene, resulting in a severe combined deficiency of serotonin, dopamine, norepinephrine, and epinephrine. Birth prevalence of AADCD varies by population. In pilot studies, 3-O-methyldopa (3-OMD) was shown to be a reliable biomarker for AADCD in high-throughput newborn screening (NBS) allowing an early diagnosis and access to gene therapy. To evaluate the usefulness of this method for routine NBS, 3-OMD screening results from the largest three German NBS centers were analyzed.

METHODS

A prospective, multicenter (n = 3) NBS pilot study evaluated screening for AADCD by quantifying 3-OMD in dried blood spots (DBS) using tandem mass spectrometry (MS/MS).

RESULTS

In total, 766,660 neonates were screened from January 2021 until June 2023 with 766,647 with unremarkable AADCD NBS (766,443 by 1st-tier analysis and 204 by 2nd-tier analysis) and 13 with positive NBS result recalled for confirmatory diagnostics (recall-rate about 1:59,000). Molecular genetic analysis confirmed AADCD (c.79C > T p.[Arg27Cys] in Exon 2 und c.215 A > C p.[His72Pro] in Exon 3) in one infant. Another individual was highly suspected with AADCD but died before confirmation (overall positive predictive value 0.15). False-positive results were caused by maternal L-Dopa use (n = 2) and prematurity (30th and 36th week of gestation, n = 2). However, in 63% (n = 7) the underlying etiology for false positive results remained unexplained. Estimated birth prevalence (95% confidence interval) was 1:766,660 (95% CI 1:775,194; 1:769,231) to 1:383,330 (95% CI 1:384,615; 1:383,142). The identified child remained asymptomatic until last follow up at the age of 9 months.

CONCLUSIONS

The proposed screening strategy with 3-OMD detection in DBS is feasible and effective to identify individuals with AADCD. The estimated birth prevalence supports earlier estimations and confirms AADCD as a very rare disorder. Pre-symptomatic identification by NBS allows a disease severity adapted drug support to diminish clinical complications until individuals are old enough for the application of the gene therapy.

Fatal cervical myelopathy in a child with glutaric aciduria type 1

We report the case of a Syrian female refugee with late diagnosis of glutaric aciduria type 1 characterised by massive axial hypotonia and quadriplegia who only started adequate diet upon arrival in Switzerland at the age of 4 years, after a strenuous migration journey. Soon after arrival, she died from an unexpected severe upper cervical myelopathy, heralded by acute respiratory distress after a viral infection. This was likely due to repeated strains on her hypotonic neck and precipitated by an orthotopic os odontoideum who led to atlanto-axial subluxation. This case reminds us not to omit handling patients with insufficient postural control and hypotonia with great care to avoid progressive cervical myelopathy.

Acute fatal ventricular arrhythmia induced by severe hyperkalemia in a toddler with decompensated methylmalonic acidemia

BACKGROUND

Methylmalonic acidemia is a very rare genetic metabolic disease. Patients with isolated methylmalonic acidemia typically present with acute alterations of consciousness, failure to thrive, anorexia, vomiting, respiratory distress, and muscular hypotonia. Despite the evidence-based management, affected individuals experience significant morbidity and mortality. Hyperkalemia is one of the unusual complications of methylmalonic acidemia.

CASE PRESENTATION

In this paper, we describe a 4-year-old Persian boy with methylmalonic acidemia who developed life-threatening arrhythmia following severe hyperkalemia and metabolic acidosis. Emergent management of the condition was successfully carried out, and the rhythm changed to normal sinus rhythm by effectively reducing the serum potassium level. We discuss the possible etiology of this lethal condition and describe its management on the basis of the available evidence.

CONCLUSION

During metabolic decompensation in methylmalonic acidemia, frequent blood gas and electrolyte testing to prescribe and adjust therapy and annual echocardiogram and electrocardiogram screening are essential.

Clinical and electroencephalogram characteristics of methylmalonic acidemia with MMACHC and MUT gene mutations

OBJECTIVE

This study investigated the clinical, imaging, and electroencephalogram (EEG) characteristics of methylmalonic acidemia (MMA) with nervous system damage as the primary manifestation.

METHODS

From January 2017 to November 2022, patients with nervous system injury as the main clinical manifestation, diagnosed with methylmalonic acidemia by metabolic and genetic testing, were enrolled and analyzed. Their clinical, imaging, and electroencephalogram data were analyzed.

RESULTS

A total of 18 patients were enrolled, including 15 males and 3 females. The clinical symptoms were convulsions, poor feeding, growth retardation, disorder of consciousness, developmental delay, hypotonia, and blood system changes. There were 6 cases (33%) of hydrocephalus, 9 (50%) of extracerebral space widened, 5 (27%) of corpus callosum thinning, 3 (17%) of ventricular dilation, 3 (17%) of abnormal signals in the brain parenchyma (frontal lobe, basal ganglia region, and brain stem), and 3 (17%) of abnormal signals in the lateral paraventricular. In addition, there were 3 cases (17%) of cerebral white matter atrophy and 1 (5%) of cytotoxic edema in the basal ganglia and cerebral peduncle. EEG data displayed 2 cases (11%) of hypsarrhythmia, 3 (17%) of voltage reduction, 12(67%) of abnormal discharge, 13 (72%) of abnormal sleep physiological waves or abnormal sleep structure, 1 (5%) of immature (delayed) EEG development, and 8 (44%) of slow background. There were 2 cases (11%) of spasms, 1 (5%) of atonic seizures, and 1 (5%) of myoclonic seizures. There were 16 patients (89%) with hyperhomocysteinemia. During follow-up, 1 patient was lost to follow-up, and 1 died. In total, 87.5% (14/16) of the children had varying developmental delays. EEG was re-examined in 11 cases, of which 8 were normal, and 3 were abnormal. Treatments included intramuscular injections of vitamin B12, L-carnitine, betaine, folic acid, and oral antiepileptic therapy. Acute treatment included anti-infective, blood transfusion, fluid replacement, and correcting acidosis. The other treatments included low-protein diets and special formula milk powder.

CONCLUSION

Methylmalonic acidemia can affect the central nervous system, leading to structural changes or abnormal signals on brain MRI. Metabolic screening and genetic testing help clarify the diagnosis. EEG can reflect changes in brain waves during the acute phase.

Clinical and Molecular Genetic Analysis with Methylmalonic Acidemia Combined with Homocystinuria

BACKGROUND

Based on research, c.609G>A (p.W203X) is a universal mutation site for MMACHC in methylmalonic acidemia (MMA) combined with homocystinuria, cblC type (cblC disease), and c.467G>A (p.G156D) mutation in families with such disease have not yet been reported. To conduct clinical and molecular genetic analysis of a family with cblC disease.

METHODS

This work followed the Declaration of Helsinki. All testing methods were performed under the informed consent of our children patients' parents. A second-generation cblC family with 5 members, was selected as the research subject, including sick siblings and parents and an older sister with normal phenotype, given newborn screening for acylcarnitine spectrum via liquid chromatography tandem mass spectrometry (LC-MS/MS), and diagnosed through combining urine organic acid with homocysteine detection via gas chromatography-mass spectrometry (GC-MS) with second-generation gene sequencing technology. The peripheral blood of five family members was collected for genomic DNA extraction, and the changes were screened in disease-related MMACHC sequence via PCR and direct DNA sequencing.

RESULTS

The family conformed to the autosomal recessive inheritance, the proband and younger sister were cblC patients, diagnosed in February and at 22d given relevant treatment. The proband died, whereas the younger sister received follow-up treatment. Their parents and sister had normal phenotype. In 2 cases, there was compound heterozygous mutation in MMACHC called c.609G>A (p.W203X) nonsense mutation and c.467G>A (p.G156D) missense mutation in exon 4, while the father with normal phenotype had heterozygous mutation c.609G>A in exon 4 coding area. In its protein, the 203rd amino acid changed from tryptophan to a stop codon (p.W203 x). The normal mother and sister had a heterozygous mutation c.467G>A in exon 4 coding area. In its protein, the 156th amino acid changed from glycine to aspartic acid (p.G156D).

CONCLUSIONS

The cblC family results from c.609G>A (p.W203X) and c.467G>A (p.G156D) compound heterozygous mutations in MMACHC, which has a pathogenic impact.

Late-onset methylmalonic acidemia and homocysteinemia (cblC disease): systematic review

INTRODUCTION

Combined methylmalonic acidemia and homocystinuria, cblC type is an inborn error of intracellular cobalamin metabolism and the most common one. The age of onset ranges from prenatal to adult. The disease is characterised by an elevation of methylmalonic acid (MMA) and homocysteine and a decreased production of methionine. The aim is to review existing scientific literature of all late onset cblC patients in terms of clinical symptoms, diagnosis, and outcome.

METHODS

A bibliographic database search was undertaken in PubMed (MEDLINE) complemented by a reference list search. We combined search terms regarding cblC disease and late onset. Two review authors performed the study selection, data extraction and quality assessment.

RESULTS

Of the sixty-five articles included in this systematic review, we collected a total of 199 patients. The most frequent clinical symptoms were neuropathy/myelopathy, encephalopathy, psychiatric symptoms, thrombotic microangiopathy, seizures, kidney disease, mild to severe pulmonary hypertension with heart failure and thrombotic phenomena. There were different forms of supplementation used in the different studies collected and, within these studies, some patients received several treatments sequentially and/or concomitantly. The general outcome was: 64 patients recovered, 78 patients improved, 4 patients did not improve, or the disease progressed, and 12 patients died.

CONCLUSIONS

Most scientific literature regarding the late onset cblC disease comes from case reports and case series. In most cases treatment initiation led to an improvement and even recovery of some patients. The lack of complete recovery underlines the necessity for increased vigilance in unclear clinical symptoms for cblC disease.

A position statement on the post gene-therapy rehabilitation of aromatic I-amino acid decarboxylase deficiency patients

Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare genetic disorder of monoamine neurotransmitter synthesis that presents with a range of symptoms, including motor dysfunction and limited attainment of developmental motor milestones. The approval of eladocagene exuparvovec, a gene therapy for AADC deficiency with demonstrated efficacy for motor improvements, now expands the range of motor outcomes possible for patients with this disorder. However, recommendations and guidelines for therapy following treatment with gene therapy are lacking. To ensure patients can reach their full potential following treatment with gene therapy, it is essential they receive rehabilitation therapies designed specifically with their impairments and goals in mind. Therefore, we highlight specific rehabilitative needs of patients following gene therapy and propose a set of recommendations for the post-treatment period based on collective experiences of therapists, physicians, and caregivers treating and caring for patients with AADC deficiency who have been treated with gene therapy. These recommendations include a focus on periods of intensive therapy, facilitating active movements, training for functional abilities, cognitive and communication training, parent/caregiver empowerment, collaboration between therapists and caregivers to develop in-home programs, and the incorporation of supplemental forms of therapy that patients and their families may find more enjoyable and engaging. Many of these rehabilitative strategies may be employed prior to gene therapy. However, these recommendations will be valuable for therapists, caregivers, and wider treatment teams as they prepare for the post-treatment journey with these patients. Furthermore, the considerations and recommendations presented here may prove beneficial outside the AADC deficiency community as gene therapies and other treatments are developed and approved for other rare diseases.

Genetic analysis of isolated methylmalonic acidemia in Henan, China: c.1663G>A variant of MMUT prevalent in the Henan population

BACKGROUND

Methylmalonic acidemia (MMA) is the most common organic acidemia in China, and isolated MMA accounts for approximately 30 % of all types of MMA. Common variants of the MMUT gene vary greatly around the world. The present study aims to determine the high-frequency and novel genetic variants of the MMUT gene in the Henan population of China and evaluate the prognosis of patients carrying the c.1663G>A (p.Ala555Thr) variant.

METHODS

We performed next-generation sequencing for 41 patients with isolated MMA screened by tandem mass spectrometry (MS/MS) and analysed the genetic results. We also evaluated the prognosis of patients with the c.1663G>A variant. We used Jalview software for multispecies sequence alignment and Missense3D and DynaMut to predict the protein function of the detected novel variants.

RESULTS

A total of 43 variants from 41 patients with isolated MMA were detected, of which c.1663G>A (14.63 %), c.729_730insTT (10.98 %), and c.1106G>A (8.53 %) are high-frequency variants of the MMUT gene in the Henan population. The patients carrying the c.1663G>A variant tended to be responsive to vitamin B12, have a low mortality rate. We also identified 5 novel variants (c.479C>T, c.811G>C, c.965T>A, c.1142G>A and c.1667C>T).

CONCLUSION

The rare variant c.1663G>A is prevalent in the Henan population, and infants with this variant tend to have good prognosis. Our findings, especially novel variants, will help broaden the spectrum of genetic variants and facilitate clinical diagnosis and genetic counselling for affected families.

Adult-onset combined methylmalonic acidemia and hyperhomocysteinemia, cblC type with aortic dissection and acute kidney injury: a case report

BACKGROUND

Combined methylmalonic acidemia (MMA) and hyperhomocysteinemia, cobalamin C (cblC) type, also named cblC deficiency is a rare autosomal recessive genetic metabolic disease. It progressively causes neurological, hematologic, renal and other system dysfunction. The clinical manifestations are relatively different due to the onset time of disease.

CASE PRESENTATION

This report describes a rare case of a 26 year old man with cblC deficiency who developed life-threatening aortic dissection and acute kidney injury (AKI) and showed neuropsychiatric symptoms with elevated serum homocysteine and methylmalonic aciduria. After emergent operation and intramuscular cobalamin supplementation therapy, the male recovered from aortic dissection, neurological disorder and AKI. Finally, two previously published compound heterozygous variants, c.482G > A (p.R161Q) and c.658_660del (p.K220del) in the MMACHC gene were detected in this patient and he was confirmed to have cblC deficiency.

CONCLUSIONS

Poor cognizance of presenting symptoms and biochemical features of adult onset cblC disease may cause delayed diagnosis and management. This case is the first to depict a case of adult-onset cblC deficiency with aortic dissection. This clinical finding may contribute to the diagnosis of cblC deficiency.

Gene therapy for neurotransmitter-related disorders

Inborn errors of neurotransmitter (NT) metabolism are a group of rare, heterogenous diseases with predominant neurological features, such as movement disorders, autonomic dysfunction, and developmental delay. Clinical overlap with other disorders has led to delayed diagnosis and treatment, and some conditions are refractory to oral pharmacotherapies. Gene therapies have been developed and translated to clinics for paediatric inborn errors of metabolism, with 38 interventional clinical trials ongoing to date. Furthermore, efforts in restoring dopamine synthesis and neurotransmission through viral gene therapy have been developed for Parkinson's disease. Along with the recent European Medicines Agency (EMA) and Medicines and Healthcare Products Regulatory Agency (MHRA) approval of an AAV2 gene supplementation therapy for AADC deficiency, promising efficacy and safety profiles can be achieved in this group of diseases. In this review, we present preclinical and clinical advances to address NT-related diseases, and summarise potential challenges that require careful considerations for NT gene therapy studies.

Validity and reliability of the MetabQoL 1.0 and assessment of neuropsychiatric burden in organic acidemias: Reflections from Turkey

OBJECTIVES

The MetabQoL 1.0 is the first disease-specific health related quality of life (HrQoL) questionnaire for patients with intoxication-type inherited metabolic disorders. Our aim was to assess the validity and reliability of the MetabQoL 1.0, and to investigate neuropsychiatric burden in our patient population.

METHODS

Data from 29 patients followed at a single center, aged between 8 and 18 years with the diagnosis of methylmalonic acidemia (MMA), propionic acidemia (PA) or isovaleric acidemia (IVA), and their parents were included. The Pediatric Quality of Life Inventory (PedsQoL) was used to evaluate the validity and reliability of MetabQoL 1.0.

RESULTS

The MetabQoL 1.0 was shown to be valid and reliable (Cronbach's alpha: 0.64-0.9). Fourteen out of the 22 patients (63.6%) formally evaluated had neurological findings. Of note, 17 out of 20 patients (85%) had a psychiatric disorder when evaluated formally by a child and adolescent psychiatrist. The median mental scores of the MetabQoL 1.0 proxy report were significantly higher than those of the self report (p = 0.023). Patients with neonatal-onset disease had higher MetabQoL 1.0 proxy physical (p = 0.008), mental (p = 0.042), total scores (p = 0.022); and self report social (p = 0.007) and total scores (p = 0.043) than those with later onset disease.

CONCLUSIONS

This study continues to prove that the MetabQoL 1.0 is an effective tool to measure what matters in intoxication-type inherited metabolic disorders. Our results highlight the importance of clinical assessment complemented by patient reported outcomes which further expands the evaluation toolbox of inherited metabolic diseases.

Inborn errors of amino acid metabolism - from underlying pathophysiology to therapeutic advances

Amino acids are organic molecules that serve as basic substrates for protein synthesis and have additional key roles in a diverse array of cellular functions, including cell signaling, gene expression, energy production and molecular biosynthesis. Genetic defects in the synthesis, catabolism or transport of amino acids underlie a diverse class of diseases known as inborn errors of amino acid metabolism. Individually, these disorders are rare, but collectively, they represent an important group of potentially treatable disorders. In this Clinical Puzzle, we discuss the pathophysiology, clinical features and management of three disorders that showcase the diverse clinical presentations of disorders of amino acid metabolism: phenylketonuria, lysinuric protein intolerance and homocystinuria due to cystathionine β-synthase (CBS) deficiency. Understanding the biochemical perturbations caused by defects in amino acid metabolism will contribute to ongoing development of diagnostic and management strategies aimed at improving the morbidity and mortality associated with this diverse group of disorders.

Isovaleric aciduria identified by newborn screening: Strategies to predict disease severity and stratify treatment

Newborn screening (NBS) allows early identification of individuals with rare disease, such as isovaleric aciduria (IVA). Reliable early prediction of disease severity of positively screened individuals with IVA is needed to guide therapeutic decision, prevent life-threatening neonatal disease manifestation in classic IVA and over-medicalization in attenuated IVA that may remain asymptomatic. We analyzed 84 individuals (median age at last study visit 8.5 years) with confirmed IVA identified by NBS between 1998 and 2018 who participated in the national, observational, multicenter study. Screening results, additional metabolic parameters, genotypes, and clinical phenotypic data were included. Individuals with metabolic decompensation showed a higher median isovalerylcarnitine (C5) concentration in the first NBS sample (10.6 vs. 2.7 μmol/L; p < 0.0001) and initial urinary isovalerylglycine concentration (1750 vs. 180 mmol/mol creatinine; p = 0.0003) than those who remained asymptomatic. C5 was in trend inversely correlated with full IQ (R = -0.255; slope = -0.869; p = 0.0870) and was lower for the "attenuated" variants compared to classic genotypes [median (IQR; range): 2.6 μmol/L (2.1-4.0; 0.7-6.4) versus 10.3 μmol/L (7.4-13.1; 4.3-21.7); N = 73]. In-silico prediction scores (M-CAP, MetaSVM, and MetaLR) correlated highly with isovalerylglycine and ratios of C5 to free carnitine and acetylcarnitine, but not sufficiently with clinical endpoints. The results of the first NBS sample and biochemical confirmatory testing are reliable early predictors of the clinical course of IVA, facilitating case definition (attenuated versus classic IVA). Prediction of attenuated IVA is supported by the genotype. On this basis, a reasonable algorithm has been established for neonates with a positive NBS result for IVA, with the aim of providing the necessary treatment immediately, but whenever possible, adjusting the treatment to the individual severity of the disease.

Late-onset cblC defect: clinical, biochemical and molecular analysis

BACKGROUND

cblC defect is the most common type of methylmalonic acidemia in China. Patients with late-onset form (>1 year) are often misdiagnosed due to heterogeneous symptoms. This study aimed to describe clinical characteristics and evaluate long-term outcomes of Chinese patients with late-onset cblC defect.

METHODS

A total of 85 patients with late-onset cblC defect were enrolled. Clinical data, including manifestations, metabolites, molecular diagnosis, treatment and outcome, were summarized and analyzed.

RESULTS

The age of onset ranged from 2 to 32.8 years old (median age 8.6 years, mean age 9.4 years). The time between first symptoms and diagnosis ranged from a few days to 20 years (median time 2 months, mean time 20.7 months). Neuropsychiatric symptoms were presented as first symptoms in 68.2% of cases, which were observed frequently in schoolchildren or adolescents. Renal involvement and cardiovascular disease were observed in 20% and 8.2% of cases, respectively, which occurred with the highest prevalence in preschool children. Besides the initial symptoms, the disease progressed in most patients and cognitive decline became the most frequent symptom overall. The levels of propionylcarnitine, propionylcarnitine / acetylcarnitine ratio, methylmalonic acid, methylcitric acid and homocysteine, were decreased remarkably after treatment (P<0.001). Twenty-four different mutations of MMACHC were identified in 78 patients, two of which were novel. The c.482G>A variant was the most frequent mutated allele in this cohort (25%). Except for 16 patients who recovered completely, the remaining patients were still left with varying degrees of sequelae in a long-term follow-up. The available data from 76 cases were analyzed by univariate analysis and multivariate logistic regression analysis, and the results showed that the time from onset to diagnosis (OR = 1.025, P = 0. 024) was independent risk factors for poor outcomes.

CONCLUSIONS

The diagnosis of late-onset cblC defect is often delayed due to poor awareness of its various and nonspecific symptoms, thus having an adverse effect on the prognosis. It should be considered in patients with unexplained neuropsychiatric and other conditions such as renal involvement, cardiovascular diseases or even multiple organ damage. The c.482G>A variant shows the highest frequency in these patients. Prompt treatment appears to be beneficial.

Streamlined determination of 3-O-methyldopa in dried blood spots: Prospective screening for aromatic l-amino-acid decarboxylase deficiency

BACKGROUND

Aromatic L-amino-acid decarboxylase (AADC) deficiency diagnosis is often delayed by low disease awareness and specific laboratory examinations. We demonstrated that an elevated concentration of L-dopa metabolite 3-O-methyldopa (3-OMD) in dried blood spots could be integrated into a newborn screening program to detect AADC deficiency.

METHODS

DBS samples for amino acid and acylcarnitine analysis using NeoBase™2 reagents were also analyzed for the 3-OMD concentration using 13C6-phenylalanine as an internal standard. For samples exceeding the pre-defined cutoffs, an additional spot was punched from the original filter paper for second-tier 3-OMD measurement by high performance liquid chromatography (HPLC)-MS/MS assay. Newborns with a 3-OMD concentration exceeding 500 ng/mL were referred for confirmatory testing.

RESULTS

From Feb. 2020 to Dec. 2022, 157,371 newborns were screened for AADC deficiency. Eight newborns exhibited an elevated 3-OMD concentration (839-5170 ng/mL). Among them, six newborns were confirmed to carry two pathogenic DDC variants, indicating an incidence of AADC deficiency of ∼1:26,000 (95% confidence interval: 1 in 12,021 to 1 in 57,228). During the follow-up period, all six patients developed typical symptoms of AADC deficiency.

CONCLUSION

The screening for 3-OMD, a target for AADC deficiency, could be easily integrated into the existing newborn screening programs and facilitate the future application for early diagnosis and effective treatment.

Biochemical and molecular features of chinese patients with glutaric acidemia type 1 from Fujian Province, southeastern China

BACKGROUND

Glutaric acidemia type 1 (GA1) is a rare autosomal recessive inherited metabolic disorder caused by variants in the gene encoding the enzyme glutaryl-CoA dehydrogenase (GCDH). The estimated prevalence of GA1 and the mutational spectrum of the GCDH gene vary widely according to race and region. The aim of this study was to assess the acylcarnitine profiles and genetic characteristics of patients with GA1 in Fujian Province, southeastern China.

RESULTS

From January 2014 to December 2022, a total of 1,151,069 newborns (631,016 males and 520,053 females) were screened using MS/MS in six newborn screening (NBS) centers in Fujian Province and recruited for this study. Through NBS, 18 newborns (13 females and 5 males) were diagnosed with GA1. Thus, the estimated incidence of GA1 was 1 in 63,948 newborns in Fujian province. In addition, 17 patients with GA1 were recruited after clinical diagnosis. All but one patient with GA1 had a remarkable increase in glutarylcarnitine (C5DC) concentrations. The results of urinary organic acid analyses in 33 patients showed that the concentration of glutaric acid (GA) increased in all patients. The levels of C5DC and GA in patients identified via NBS were higher than those in patients identified via clinical diagnosis (P < 0.05). A total of 71 variants of 70 alleles were detected in patients with GA1, with 19 different pathogenic variants identified. The three most prevalent variants represented 73.23% of the total and were c.1244-2 A > C, p.(?) (63.38%), c.1261G > A, p.Ala421Thr (5.63%), and c.406G > T, p.Gly136Cys (4.22%). The most abundant genotype observed was c.[1244-2 A > C]; [1244-2 A > C] (18/35, 52.43%) and its phenotype corresponded to high excretors (HE, GA > 100 mmol/mol Cr).

CONCLUSIONS

In conclusion, we investigated the biochemical and molecular features of 35 unrelated patients with GA1. C5DC concentrations in dried blood spots and urinary GA are effective indicators for a GA1 diagnosis. Our study also identified a GCDH variant spectrum in patients with GA1 from Fujian Province, southeastern China. Correlation analysis between genotypes and phenotypes provides preliminary and valuable information for genetic counseling and management.

Pearls & Oy-sters: Late-Onset Cobalamin C Deficiency Presenting With Subacute Combined Degeneration

Cobalamin C (CblC) deficiency is a rare inborn error in cobalamin (vitamin B12) metabolism which results in impaired intracellular processing of dietary vitamin B12. This leads to a wide range of clinical manifestations including cognitive impairment, psychiatric symptoms, myelopathy, thrombotic events, glomerulonephritis, and pulmonary arterial hypertension. CblC deficiency typically presents in the pediatric population but can also present in adulthood. Diagnosis in adults can be challenging due to the rarity of this condition and its myriad clinical presentations. CblC deficiency is treatable, so early diagnosis is important in preventing permanent neurologic damage. Although CblC deficiency results from a defect in vitamin B12 metabolism, B12 levels remain normal. Diagnosis depends on testing metabolites altered by vitamin B12 dysfunction such as methylmalonic acid (MMA) and homocysteine. We presented a case of a 20-year-old woman who presented with chronic progressive lower extremity weakness and sensory changes. She was eventually diagnosed with subacute combined degeneration because of CblC deficiency and effectively treated. This case highlights the importance of considering inborn errors of metabolism in adult patients and including testing of metabolites such as MMA and homocysteine when suspecting vitamin B12 dysfunction.

A DEADLY CASE OF DEHYDRATION: ORGANIC ACIDEMIAS IN THE EMERGENCY DEPARTMENT

BACKGROUND

Organic acidemias are rare genetic mutations, most commonly identified in the newborn period. Late-onset presentations present a diagnostic conundrum. Early identification and appropriate management can be lifesaving.

CASE REPORT

We describe the case of a 3-year-old boy who presented to urgent care with 2 days of nausea, vomiting, and diarrhea followed by respiratory distress, shock, and encephalopathy. Brisk recognition of his shock state led to an urgent transfer to a tertiary care pediatric emergency department by air where his shock was treated and hyperammonemia was uncovered, leading to the diagnosis of late-onset propionic acidemia, which was subsequently managed with a good outcome. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Late-onset presentations of inborn errors of metabolism, including organic acidemias, represent one of the most challenging pediatric cases an emergency physician can encounter. This case reviews the management and diagnosis of a late-onset inborn error of metabolism and emphasizes how prompt diagnosis and treatment can lead to a favorable outcome.

Long-term anthropometric development of individuals with inherited metabolic diseases identified by newborn screening

Newborn screening (NBS) for inherited metabolic diseases (IMDs) substantially shortens a patient's journey. It enables the early start of metabolic treatment which might prevent potentially lethal neonatal disease manifestations, while promoting favorable development and long-term clinical outcomes. This study aims to assess growth in screened individuals with IMDs under different dietary regimes. Anthropometric data (3585 prospective measures) of 350 screened individuals with IMDs born between 1999 and 2018 and participating in a German prospective multicenter observational study were evaluated. Overall, birth measures were within the reference ranges, suggesting unaffected prenatal growth, except for phenylketonuria (weight) and glutaric aciduria Type 1 (head circumference). After birth, longitudinal analysis of anthropometric measures revealed a loss of height standard deviation score (SDS; -0.5 SDS; p < 0.0001), head circumference SDS (-0.2 SDS; p = 0.0028), but not for weight SDS (0.1 SDS; p = 0.5097) until the age of 18 years, while BMI SDS increased (0.4 SDS; p < 0.0001). The significant interaction with age and diet groups was pronounced for the linear growth in individuals receiving diets being low in protein, long-chain triglycerides, and galactose (p < 0.001). Identification by NBS and subsequent early (dietary) treatment cannot completely protect against alterations in growths. Disease-specific (e.g., metabolic impairments, neurotoxins) and dietary-specific (e.g., diets reduced in protein) factors may have an amplified impact on longitudinal growth. Therefore, alongside other important follow-ups, the continuous observation of the anthropometric development of screened individuals with IMDs needs special attention to early identify and support individuals at risk.

Burden and severity of disease of aromatic L-amino acid decarboxylase deficiency: a systematic literature review

OBJECTIVE

The objective was to investigate the severity of aromatic L-amino acid decarboxylase deficiency (AADCd) as reported in the published literature and to collate evidence of the clinical manifestations of AADCd, and the impact of the disease on patients, caregivers, and healthcare systems.

METHODS

Published articles reporting severity of disease or disease impact were eligible for inclusion in this review. Articles were searched in MEDLINE, EMBASE, Cochrane CENTRAL, TRIP medical, and CRD databases in October 2021. The quality of the included studies was investigated using a modified version of the grading system of the Centre for Evidence-Based Medicine (CEBM). Descriptive data of the literature was extracted and a narrative synthesis of the results across studies was conducted. This review is reported according to the PRISMA reporting guidelines for systematic reviews.

RESULTS

The search identified 970 unique reports, of which 59 met eligibility criteria to be included in the review. Of these, 48 included reports provided details on the clinical manifestations of AADCd. Two reports explored the disease impact on patients, while four described the impact on caregivers. Five reports assessed the impact on healthcare systems. Individuals with AADCd experience very severe clinical manifestations regardless of motor milestones achieved, and present with a spectrum of other complications. Individuals with AADCd present with very limited function, which, in combination with additional complications, substantially impact the quality-of-life of individuals and their caregivers. The five studies which explore the impact on the healthcare system reported that adequate care of individuals with AADCd requires a vast array of medical services and supportive therapies.

CONCLUSIONS

Irrespective of the ambulatory status of individuals, AADCd is a debilitating disease that significantly impacts quality-of-life for individuals and caregivers. It impacts the healthcare system due to the need for complex coordinated activities of a multidisciplinary specialist team.

[Genetic variant analysis and prenatal diagnosis for Chinese pedigrees affected with cblC methylmalonic acidemia]

OBJECTIVE

To detect variants of the MMACHC gene among 110 ethnic Han Chinese pedigrees affected with metabolic deficiency methylmalonic acidemia (MMA) of cobalamin C (cblC).

METHODS

Peripheral blood samples were collected from the probands and their parents. Following DNA extraction, the coding regions of the MMACHC gene were subjected to PCR amplification, Sanger sequencing and quantitative PCR assaying. For 48 pedigrees, chorionic villus samples were taken for prenatal genetic diagnosis.

RESULTS

Thirty five types of variants were detected among the 110 pedigrees, which included missense, nonsense, frameshifting, splicing variants and exonic deletions. Most variants have occurred in exons 4 (73.18%). The detection rate for c.609G>A (p.Trp203Ter) variant was the highest (33.64%), followed by c.658_660delAAG (12.27%), c.567dupT (9.09%) and c.80A>G (6.82%). Two variants, namely c.57_58insT (p.Gly20Trpfs*14) and c.505_506delAT (p.Ile169Argfs*12), were unreported previously and both were of frameshifting types. For the 48 pedigrees undergoing prenatal diagnosis, 14 fetuses were found to be normal, 24 have carried heterozygous variants, the remaining 10 have carried compound heterozygous or homozygous variants.

CONCLUSION

The discovery of the two novel variants has expanded the spectrum of the MMACHC gene variants among ethnic Han population. Above finding has provide a basis for the prenatal diagnosis and genetic counseling for the affected pedigrees.

Very long-term outcomes in 23 patients with cblA type methylmalonic acidemia

OBJECTIVES

To present the very long-term follow up of patients with cobalamin A (cblA) deficiency.

METHODS

A retrospective case series of adult (>16 years) patients with molecular or enzymatic diagnosis of cblA deficiency.

RESULTS

We included 23 patients (mean age: 27 ± 7.6 years; mean follow-up: 24.9 ± 7.6 years). Disease onset was mostly pediatric (78% < 1 year, median = 4 months) with acute neurologic deterioration (65%). Eight patients presented with chronic symptoms, and one had an adult-onset mild cblA deficiency. Most of the patients (61%) were initially classified as vitamin B12-unresponsive methylmalonic aciduria (MMA); in vitro B12 responsiveness was subsequently found in all the tested patients (n = 13). Initial management consisted of protein restriction (57%), B12 (17%), or both (26%). The main long-term problems were intellectual disability (39%) and renal failure (30%). However, 56.5% of the patients were living independently. Intellectual disability was equally distributed among the initial treatment groups, while renal failure (moderate and beginning at the age of 38 years) was present in only one out of seven patients initially treated with B12.

CONCLUSIONS

We provide a detailed picture of the long-term outcome of a series of adult cblA patients, mostly diagnosed before the enzymatic and molecular era. We confirm that about 35% of the patients do not present acutely, underlining the importance of measuring MMA in any case of unexplained chronic renal failure, intellectual disability, or growth delay. In addition, we describe a patient with a milder adult-onset form. Early B12 supplementation seems to protect from severe renal insufficiency.

[Differential diagnosis of a Chinese pedigree with methylmalonic acidemia by next-generation sequencing]

OBJECTIVE

To explore the genetic etiology of a child with suspected propionic acidemia.

METHODS

Genomic DNA was extracted from peripheral blood sample of the child and subjected to high-throughput sequencing to screen pathogenic variants of genes associated with methylmalonic acidemia and propionic acidemia, including MUT, MMACHC, MMAA, MMAB, MMADHC, LMBRD1, PCCA, PCCB and SLC22A5. Candidate variants were verified by Sanger sequencing of the proband, her parents and sister.

RESULTS

The proband was found to harbor two pathogenic variants of the MUT gene, namely c.1560+2T>C and c.729_730insTT (p.Asp244fs), but not in genes associated with propionic acidemia. Her sister and father had carried c.1560+2T>C, and her mother had carried c.729_730insTT (p.Asp244fs).

CONCLUSION

The proband was diagnosed as methylmalonic acidemia due to compound heterozygous variants of c.1560+2T>C and c.729_730insTT (p.Asp244fs) of the MUT gene. Her elder sister and parents were all carriers. Genetic testing has facilitated differential diagnosis of methylmalonic acidemia and propionic acidemia in this pedigree.

[Factors affecting phenotypes in the patients with MMACHC gene c.609G>A homozygous variant cblC type methylmalonic acidemia combined with homocysteinuria]

OBJECTIVE

To investigate the factors affecting phenotypes in the patients of methylmalonic acidemia combined with homocysteinemia cblC type with MMACHC c.609G>A homologous variant.

METHODS

A retrospective study on the clinical manifestations, complications, treatment, and outcome in 164 patients of cblC type with MMACHC c.609G>A homologous variant was conducted. The patients were diagnosed by biochemical and genetic analysis from January 1998 to December 2020.

RESULTS

Among the 164 patients, 2 cases were prenatally diagnosed and began treatment after birth. They are 3 and 12 years old with normal physical and mental development. Twenty-one cases were diagnosed by newborn screening. Among them, 15 cases had with normal development. They were treated from the age of two weeks at the asymptomatic period. Six cases began treatment aged 1 to 3 months after onset. Their development was delayed. One hundred and forty-one cases were clinically diagnosed. Their onset age ranges from a few minutes after birth to 6 years old. 110 cases had early-onset (78.0%). 31 cases had late-onset (22.0%). Five of them died. 24 patients lost to follow-up. Of the 141 clinically diagnosed patients, 130 (92.2%) with psychomotor retardation, 69 (48.9%) with epilepsy, 39 (27.7%) with anemia, 30 (21.3%) had visual impairment, 27 (19.1%) had hydrocephalus, 26 (18.4%) had feeding difficulties, 7 (5.0%) with liver damage, and 5 (3.5%) with metabolic syndrome. The frequency of hydrocephalus and seizures was significantly higher in the early-onset group. The urinary methylmalonic acid increased significantly in the patients with epilepsy. During the long-term follow-up, the level of plasma total homocysteine in the seizure-uncontrolled group was significantly higher than that in the seizure-controlled group, the difference had a statistical significance (P<0.05).

CONCLUSION

Most of the patients with MMACHC c.609G>A homozygous variant had early-onset disease, with a high mortality and disability rate. If not treated in time, it will lead to neurological damage, resulting in epilepsy, mental retardation, hydrocephalus, and multiple organ damage. Pre-symptomatic diagnosis and treatment are crucial to prevent irreversible neurological damage. Neonatal screening and prenatal diagnosis are important to improve the outcome of the patients.

[Disease spectrum analysis of children with inherited metabolic diseases detected by gas chromatography-mass spectrometry of urinary organic acids]

Objective: To investigate the spectrum of amino acid, organic acid, and fatty acid oxidative metabolic diseases in children diagnosed by detecting urinary organic acid levels using gas chromatography-mass spectrometry. Methods: From January 2005 to December 2021, clinical data of 2 461 children diagnosed with inherited metabolic diseases (IMD) by gas chromatography-mass spectrometry, in combination with tandem mass spectrometry and genetic testing in Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were retrospectively analyzed. Results: Among 2 461 children, 1 446 were male and 1 051 were female. A total of 32 types of IMD were detected among 2 461 patients, which included 10 amino acid disorders in 662 cases (26.9%), 6 common diseases were hyperphenylalaninemia, citrin deficiency, ornithine carbamoyltransferase deficiency, maple syrup urine disease, alkaptonuria, and tyrosinemia-I, 17 types of organic acidemias in 1 683 cases (68.4%), 6 common diseases were methylmalonic acidemia, propionic acidemia, valeric acidemia-type Ⅰ, isovaleric acidemia, 3-methylcrotonyl-CoA carboxylase deficiency and multiple carboxylase deficiency and 5 fatty acid β oxidative defects in 116 cases (4.7%), 2 common diseases were multiple acyl-CoA dehydrogenase deficiency and short-chain acyl-CoA dehydrogenase deficiency). Conclusion: Among the diseases diagnosed by analyzing urinary organic acid profiling with gas chromatography-mass spectrometry, the most common are organic acidemias, followed by amino acid disorders and fatty acid oxidation defects.

Review of neuropsychological outcomes in isolated methylmalonic acidemia: recommendations for assessing impact of treatments

Methylmalonic acidemia (MMA) due to methylmalonyl-CoA mutase deficiency (OMIM #251,000) is an autosomal recessive disorder of organic acid metabolism associated with life-threatening acute metabolic decompensations and significant neuropsychological deficits. "Isolated" MMA refers to the presence of excess methylmalonic acid without homocysteine elevation. Belonging to this class of disorders are those that involve complete deficiency (mut⁰) and partial deficiency (mut^-) of the methylmalonyl-CoA mutase enzyme and other disorders causing excess methylmalonic acid excretion. These other disorders include enzymatic subtypes related to cobalamin A defect (cblA) (OMIM #25,110), cobalamin B defect (cblB) (OMIM #251,110) and related conditions. Neuropsychological attributes associated with isolated MMA have become more relevant as survival rates increased following improved diagnostic and treatment strategies. Children with this disorder still are at risk for developmental delay, cognitive difficulties and progressive declines in functioning. Mean IQ for all types apart from cblA defect enzymatic subtype is rarely above 85 and much lower for mut⁰ enzymatic subtype. Identifying psychological domains responsive to improvements in biochemical status is important. This review suggests that processing speed, working memory, language, attention, and quality of life may be sensitive to fluctuations in metabolite levels while IQ and motor skills may be less amenable to change. Due to slower developmental trajectories, Growth Scale Values, Projected Retained Ability Scores and other indices of change need to be incorporated into clinical trial study protocols. Neuropsychologists are uniquely qualified to provide a differentiated picture of cognitive, behavioral and emotional consequences of MMA and analyze benefits or shortcomings of novel treatments.

[Genetic analysis of 21 cases of methylmalonic acidemia]

OBJECTIVE

To carry out genetic analysis for 21 patients with methylmalonic acidemia (MMA) and provide genetic counseling for their families.

METHODS

Next generation sequencing (panel) was used to detect the pathogenic variants underlying the disease.

RESULTS

In total 29 variant sites of MMUT, MMAA, MMUT were identified in the 21 patients, with common variants including c.323G>A (10%), c.917C>T (10%), c.984delC (10%) of MMUT gene, and c.609G>A (45%), c.80A>G (10%) , c.567dupT (10%) of MMACHC gene. Among these, c.2000A>G of MMUT, c.298G>T of MMACHC and c.734-7A>G of MMAA gene were unreported previously.

CONCLUSION

Genetic testing for MMA patients can clarify the cause of the disease and provide a basis for the clinical diagnosis. Discovery of novel variants has enriched the mutational spectrum of MMA.

Investigation and Analysis of Blood Biochemical Indexes and Molecular Biology of Methylmalonic Acidemia

BACKGROUND

To compare MMA-related gene mutations in MMA children and the population in Qingdao, discuss the blood propionyl carnitine (C3), free carnitine (C0) methionine (MET), the mutual ratio and division difference in normal group, carrier group, and MMA group to analyze the relationship between some hotspot mutations and biochemical indicators.

METHODS

In total 3,700 newborns testing negative in tandem mass spectrometry (MS/MS) were selected at random and submitted for testing 8 pathogenic sites in MMACHC and 10 in MMUT. The gene mutations in 84 cases with detected mutation genes and 42 diagnosed children were compared. The levels and concentration distribution of C3, C0, MET, C3/C2, C3/C0, C3/MET in the blood samples of three groups were analyzed as well as the difference of biochemical indicators in newborns with hotspot mutations (c.609A>G, c.482G>A, and c.658-660delAAG).

RESULTS

All 8 pathogenic mutations in MMACHC in the population were detected and were basically consistent with the mutation types and frequency order in MMA group. The first three were c.609G>A, c.482G>A, and c.658_660delAAG. There were more types of mutation sites detected in MMA group than carrier group. Five out of 10 MMUT gene mutations were detected in the population, and 9 MMUT gene mutation sites were detected in MMA group. The findings in the two groups and the preset sites were not completely consistent. C3, C0, C3/C2, C3/C0, C3/MET in MMA group were higher than carrier and normal groups, and the difference was statistically significant; the MET in MMA group was lower than carrier and normal groups, and the difference was statistical¬ly significant. Based on the three sets of data distribution graphs, C3, C3/C2, C3/C0, and C3/MET were well distinguished. There were differences in the average C3 and C0 levels between carrier and normal groups, but with an obvious cross distribution in the graphs, and no difference in other indicators. In contrast to non-carrier group, C0, C3, C3/C0, C3/C2, and C3/MET concentration levels were higher in 609A>G mutation group, while MET level was lower, with statistical significance; in c.482G>A mutation group, C3, C3/C0, C3/C2, and C3/MET concentration levels were lower than non-carrier group, while MET level was higher, with statistical significance; in c.658-660delAAG mutation group, C0, C3, C3/C0, C3/C2, MET, and C3/MET concentration levels were not statistically different in contrast to other groups.

CONCLUSIONS

The top three mutations in MMA children in Qingdao area are c.609A>G, c.482G>A, c.658-660del AAG mutations in MMAHC; C3, C3/C2, C3/C0 can be used as specific prompt indicators for MMA screening; C3, C3/C2, C3/C0, C3/MET can be used as specific prompt indicators for combined MMA screening; abnormalities in biochemical indicators in hotspot mutation group intuitively explains c.609A>G mutation and early-onset MMA. c.482G>A mutation links with late-onset MMA.

Standardizing genetic and metabolic consults for non-accidental trauma at a large pediatric academic center

BACKGROUND

Evaluations of suspected non-accidental trauma (NAT) often include consultation with genetic and metabolic teams to assess patients for rare genetic conditions that can mimic or exacerbate child abuse. Diagnoses that may be questioned during court proceedings include osteogenesis imperfecta (OI) and glutaric aciduria type 1 (GA1). Currently there are no official society guidelines for the genetic or metabolic workup of suspected NAT.

OBJECTIVE

To standardize consult recommendations for suspected NAT through collaboration between the Genetics and Genomics Division and the Child Protection Team (CPT).

PARTICIPANTS AND SETTINGS

Children evaluated for suspected NAT at a single pediatric referral center.

METHODS

A year of inpatient consult requests for suspected NAT to the genetics division were reviewed. The most common indications for consult were fractures and subdural hematoma. Consult recommendations for similar indications varied between providers. A standard operating procedure (SOP) with specific recommendations for suspected NAT consults for fractures, intracranial hemorrhage, and other indications was created based on expert reviews and other relevant literature. A questionnaire assessing division practice patterns for these consults was distributed both pre (n = 17) and post-introduction of the SOP (n = 11).

RESULTS

Adherence to the SOP and impact on suspected NAT consult recommendations were assessed at 18 months after SOP introduction. Consult recommendations were in line with the SOP for 7/11 consults pre-intervention and 6/7 consults post-intervention. Providers were more likely to report feeling extremely or very confident they were using evidence-based medicine for NAT consults post-intervention.

Biomarkers for drug development in propionic and methylmalonic acidemias

There is an unmet need for the development and validation of biomarkers and surrogate endpoints for clinical trials in propionic acidemia (PA) and methylmalonic acidemia (MMA). This review examines the pathophysiology and clinical consequences of PA and MMA that could form the basis for potential biomarkers and surrogate endpoints. Changes in primary metabolites such as methylcitric acid (MCA), MCA:citric acid ratio, oxidation of ¹³ C-propionate (exhaled ¹³ CO₂ ), and propionylcarnitine (C3) have demonstrated clinical relevance in patients with PA or MMA. Methylmalonic acid, another primary metabolite, is a potential biomarker, but only in patients with MMA. Other potential biomarkers in patients with either PA and MMA include secondary metabolites, such as ammonium, or the mitochondrial disease marker, fibroblast growth factor 21. Additional research is needed to validate these biomarkers as surrogate endpoints, and to determine whether other metabolites or markers of organ damage could also be useful biomarkers for clinical trials of investigational drug treatments in patients with PA or MMA. This review examines the evidence supporting a variety of possible biomarkers for drug development in propionic and methylmalonic acidemias.

A case of methylmalonic acidemia and homocysteinemia cblX type with negative tandem mass spectrometry testing

A child with methylmalonic acidemia and homocysteinemia cblX type presented focal seizures and epileptic spasms in early infancy, but the tandem mass spectrometry tests showed negative results during neonatal screening or acute attack. Despite treated with a variety of antiepileptic drugs, the child died at age of The blood spot sample of the patient was retrospectively tested with ultrahigh performance liquid chromatography-tandem mass spectrometry, and the increased levels of methylmalonic acid and homocysteine were revealed. Whole exome sequencing showed that the proband had a c.202C>G(p.Q68E) hemizygous mutation in gene, which was inherited from his mother.

Approaches for diagnosis and treatment in neurotransmitter disorders of childhood

Neurotransmitter disorders are a group of neurometabolic syndromes caused by disturbances of neurotransmitter metabolism. The primary aim of this retrospective study is to present patients with disturbances of monoamine neurotransmitter metabolism. Cerebrospinal fluid (CSF) neurotransmitter measurements and genetic analysis were performed on five patients. Five patients who had various movement disorders and motor and cognitive disabilities were included. Four patients were diagnosed with sepiapterin reductase (SR) deficiency, and one was diagnosed with aromatic L-amino acid decarboxylase (AADC) deficiency. Different treatment responses appeared in patients with SR and AADC deficiency. The responses to drug treatment ranged from good to weak in our patients. The diagnosis process is challenging in patients with SR and AADC deficiency, which present similar clinical features to other neurological and metabolic diseases. Investigations of neurotransmitters in CSF and analysis of related genes are essential to differentiate disturbances of monoamine neurotransmitter metabolism from other neurometabolic diseases. For patients with monoamine neurotransmitter disorders, drugs that target these disturbances should be combined as necessary to produce the appropriate response.

Cerebrospinal Fluid Biogenic Monoamine Analysis for Diagnosis of Primary Neurotransmitter Disorders

Biogenic amine neurotransmitters metabolism is a multistep pathway with pterin and pyridoxal phosphate (vitamin B6) as cofactors. A defect in biogenic amine and cofactor metabolism and vesicular transporters result in a primary neurotransmitter disorders. These are a well-recognized groups of inherited disorders and often present with features overlapping with other neurological conditions. Their diagnosis is made by analysis of biogenic amine metabolites in cerebrospinal fluid (CSF) and other body fluids and respective enzyme assays. Many of these disorders are treatable and deficits can be reverted by timely intervention. CSF biogenic amine or cofactor metabolite analysis is one of the primary indicators of a neurotransmitter disorder. In this paper, 3 cases are reported-2 of cofactor deficiency and 1 with enzyme deficiency wherein biogenic amine estimation has assisted in diagnosis.

Selective screening for inborn errors of metabolism by tandem mass spectrometry at Sohag University Hospital, Egypt

BACKGROUND

Inborn errors of metabolism (IEMs) comprise a group of inherited diseases that can have devastating consequences and cause irreversible damage to different body systems and even lead to death. Newborn screening helps in the presymptomatic diagnosis of many medical disorders including IEMs. Early diagnosis and management of IEMs helps reduce morbidity and mortality.

OBJECTIVE

This study aimed to estimate the prevalence of IEMs among at-risk children and contribute toward early diagnosis and management in order to minimize morbidity and mortality.

METHODS

This prospective study was conducted at the Pediatrics and Neonatology Department, Sohag University Hospital, Egypt. The study enrolled 308 participants suspected of having IEMs. Cases were included based on the presence of any of the following: unexplained convulsions, persistent metabolic acidosis, persistent hypoglycemia, disturbed consciousness, delayed milestones, or family history of previous sibling death with IEMs or sibling death with a history suggestive of IEMs. All participants in the study were subjected to metabolic screening by tandem mass spectrometry (MS/MS).

RESULTS

Out of 308 neonates, 93 (30.2%) were diagnosed with IEMs. The most common diagnosis was phenylketonuria, followed by glutaric aciduria type 1 and maple syrup urine disease (43%, 19.4%, and 14%, respectively). Five patients had Canavan disease, four had medium-chain acyl CoA dehydrogenase deficiency, three had congenital lactic acidosis, two had methylmalonic acidemia, and two had primary carnitine deficiency. Propionic acidemia, isovaleric acidemia, homocystinuria, short-chain acyl CoA dehydrogenase deficiency, B-ketothiolase deficiency, and ketone body utilization defect were diagnosed in one patient each. Most patients improved (73.1%) following proper specific management.

CONCLUSION

We recommend newborn screening for IEMs using MS/MS, which may help with the early diagnosis and management of this group of disorders.

3-Hydroxyisobutyrate dehydrogenase (HIBADH) deficiency-A novel disorder of valine metabolism

3-Hydroxyisobutyric acid (3HiB) is an intermediate in the degradation of the branched-chain amino acid valine. Disorders in valine degradation can lead to 3HiB accumulation and its excretion in the urine. This article describes the first two patients with a new metabolic disorder, 3-hydroxyisobutyrate dehydrogenase (HIBADH) deficiency, its phenotype and its treatment with a low-valine diet. The detected mutation in the HIBADH gene leads to nonsense-mediated mRNA decay of the mutant allele and to a complete loss-of-function of the enzyme. Under strict adherence to a low-valine diet a rapid decrease of 3HiB excretion in the urine was observed. Due to limited patient numbers and intrafamilial differences in phenotype with one affected and one unaffected individual, the clinical phenotype of HIBADH deficiency needs further evaluation.

Subdural hematoma in glutaric aciduria type 1: High excreters are prone to incidental SDH despite newborn screening

Subdural hematoma (SDH) was initially reported in 20% to 30% of patients with glutaric aciduria type 1 (GA1). A recent retrospective study found SDH in 4% of patients, but not in patients identified by newborn screening (NBS). 168 MRIs of 69 patients with GA1 (age at MRI 9 days - 73.8 years, median 3.2 years) were systematically reviewed for presence of SDH, additional MR and clinical findings in order to investigate the frequency of SDH and potential risk factors. SDH was observed in eight high-excreting patients imaged between 5.8 and 24.4 months, namely space-occupying SDH in two patients after minor accidental trauma and SDH as an incidental finding in six patients without trauma. In patients without trauma imaged at 3 to 30 months (n = 36, 25 NBS, 27/9 high/low excreters), incidence of SDH was 16.7% (16% in NBS). SDH was more common after acute (33.3%) than insidious onset of dystonia (14.3%) or in asymptomatic patients (5.9%). It was only seen in patients with wide frontoparietal CSF spaces and frontotemporal hypoplasia. High excreters were over-represented among patients with SDH (6/27 vs 0/9 low excreters), acute onset (10/12), and wide frontoparietal CSF spaces (16/19). Incidental SDH occurs despite NBS and early treatment in approximately one in six patients with GA1 imaged during late infancy and early childhood. Greater risk of high excreters is morphologically associated with more frequent enlargement of external CSF spaces including frontotemporal hypoplasia, and may be furthered aggravated by more pronounced alterations of cerebral blood volume and venous pressure.

Characterization of variants of uncertain significance in isovaleryl-CoA dehydrogenase identified through newborn screening: An approach for faster analysis

INTRODUCTION

Clinical standard of care for newborn screening (NBS) is acylcarnitine metabolites quantitation by tandem mass spectrometry (MS/MS) from dried blood spots. Follow up sequencing often results in identification of one or more variants of uncertain significance (VUS). Isovaleric acidemia (IVA) is an autosomal recessive inborn error of metabolism caused by deficiency of isovaleryl-CoA dehydrogenase (IVDH) in the Leu catabolism pathway. Many IVD mutations are characterized as VUS complicating IVA clinical diagnoses and treatment. We present a testing platform approach to confirm the functional implication of VUS identified in newborns with IVA applicable to multiple inborn errors of metabolism identified by NBS.

METHODS

An IVD null HEK293T cell culture model was generated by using a dual sgRNA CRISPR/Cas9 genome-editing strategy targeting IVD exons 2-3. Clonal cell lines were confirmed by a combination of genomic breakpoint sequencing and droplet digital PCR. The IVD null model had no IVDH antigen signal and 96% reduction in IVDH enzyme activity. The IVD null model was transfected with vectors containing control or variant IVD and functional assays were performed to determine variant pathogenicity.

RESULTS

c.149G > C (p.Arg50Pro; precursor numbering), c.986T > C (p.Met329Thr), and c.1010G > A (p.Arg337Gln), c.1179del394 f. mutant proteins had reduced IVDH protein and activity. c.932C > T (p.Ala311Val), c.707C > T (p.Thr236Ile), and c.1232G > A (p.Arg411Gln) had stable IVDH protein, but no enzyme activity. c.521T > G (p.Val174Gly) had normal IVDH protein and activity. IVD variant transfection results confirmed results from IVA fibroblasts containing the same variants.

CONCLUSIONS

We have developed an IVD null HEK293T cell line to rapidly allow determination of VUS pathogenicity following identification of novel alleles by clinical sequencing following positive NBS results for suspected IVA. We suggest similar models can be generated via genome-editing for high throughput assessment of VUS function for a multitude of inborn errors of metabolism and can ideally supplement NBS programs.

Phenotypic and genotypic analysis of children with methylmalonic academia: A single-center study in China and a recent literature review

BACKGROUND

Methylmalonic acidemia (MMA) is a rare inherited metabolic disease caused by methylmalonyl-CoA deficiency or cobalamin metabolism disorder. It is mainly inherited in autosomal recessive mode. According to whether combined with homocysteinemia and the causative genes, it can be divided into many different subtypes. Early diagnosis and early treatment can significantly improve the prognosis.

METHODS

The children with MMA diagnosed in Tianjin Children's Hospital from 2012 to 2020 were collected. All the children underwent comprehensive physical and laboratory examinations. The metabolites in blood and urine were screened by mass spectrometry. Sanger sequencing, Next-generation sequencing and methylation detection were used for gene detection.

RESULTS

The detection rate of MMA was 0.20% in children with high-risk of inherited metabolic diseases. The three most common clinical phenotypes of children with MMA were respiratory / metabolic acidosis, global developmental delay and anemia, which were found in 36.00%, 33.33% and 30.67% of children respectively. The most common mutations of MMACHC gene in children with cblC were c.609G > A, c.658_660delAAG and c.80A > G, with frequencies of 34.09%, 13.64% and 13.64%, respectively.

CONCLUSIONS

This research expands the study of phenotype and genotype of MMA in Chinese population, and can provide reference for clinical diagnosis and treatment of MMA.

Newborn screening and disease variants predict neurological outcome in isovaleric aciduria

Isovaleric aciduria (IVA), a metabolic disease with severe (classic IVA) or attenuated phenotype (mild IVA), is included in newborn screening (NBS) programs worldwide. The long-term clinical benefit of screened individuals, however, is still rarely investigated. A national, prospective, observational, multi-center study of individuals with confirmed IVA identified by NBS between 1998 and 2018 was conducted. Long-term clinical outcomes of 94 individuals with IVA were evaluated, representing 73.4% (for classic IVA: 92.3%) of the German NBS cohort. In classic IVA (N = 24), NBS prevented untimely death except in one individual with lethal neonatal sepsis (3.8%) but did not completely prevent single (N = 10) or recurrent (N = 7) metabolic decompensations, 13 of them occurring already neonatally. IQ (mean ± SD, 90.7 ± 10.1) was mostly normal but below the reference population (P = .0022) and was even lower in individuals with severe neonatal decompensations (IQ 78.8 ± 7.1) compared to those without crises (IQ 94.7 ± 7.5; P = .01). Similar results were obtained for school placement. In contrast, individuals with mild IVA had excellent neurocognitive outcomes (IQ 105.5 ± 15.8; normal school placement) and a benign disease course (no metabolic decompensation, normal hospitalization rate), which did not appear to be impacted by metabolic maintenance therapy. In conclusion, NBS reduces mortality in classic IVA, but does not reliably protect against severe neonatal metabolic decompensations, crucial for favorable neurocognitive outcome. In contrast, individuals with mild IVA had excellent clinical outcomes regardless of metabolic maintenance therapy, questioning their benefit from NBS. Harmonized stratified therapeutic concepts are urgently needed.

Guidelines for the diagnosis and management of methylmalonic acidaemia and propionic acidaemia: First revision

Isolated methylmalonic acidaemia (MMA) and propionic acidaemia (PA) are rare inherited metabolic diseases. Six years ago, a detailed evaluation of the available evidence on diagnosis and management of these disorders has been published for the first time. The article received considerable attention, illustrating the importance of an expert panel to evaluate and compile recommendations to guide rare disease patient care. Since that time, a growing body of evidence on transplant outcomes in MMA and PA patients and use of precursor free amino acid mixtures allows for updates of the guidelines. In this article, we aim to incorporate this newly published knowledge and provide a revised version of the guidelines. The analysis was performed by a panel of multidisciplinary health care experts, who followed an updated guideline development methodology (GRADE). Hence, the full body of evidence up until autumn 2019 was re-evaluated, analysed and graded. As a result, 21 updated recommendations were compiled in a more concise paper with a focus on the existing evidence to enable well-informed decisions in the context of MMA and PA patient care.

Impact of interventional and non-interventional variables on anthropometric long-term development in glutaric aciduria type 1: A national prospective multi-centre study

Glutaric aciduria type 1 (GA1) is a rare neurometabolic disorder, caused by inherited deficiency of glutaryl-CoA dehydrogenase, mostly affecting the brain. Early identification by newborn screening (NBS) significantly improves neurologic outcome. It has remained unclear whether recommended therapy, particular low lysine diet, is safe or negatively affects anthropometric long-term outcome. This national prospective, observational, multi-centre study included 79 patients identified by NBS and investigated effects of interventional and non-interventional parameters on body weight, body length, body mass index (BMI) and head circumference as well as neurological parameters. Adherence to recommended maintenance and emergency treatment (ET) had a positive impact on neurologic outcome and allowed normal anthropometric development until adulthood. In contrast, non-adherence to ET, resulting in increased risk of dystonia, had a negative impact on body weight (mean SDS -1.07; P = .023) and body length (mean SDS -1.34; P = -.016). Consistently, longitudinal analysis showed a negative influence of severe dystonia on weight and length development over time (P < .001). Macrocephaly was more often found in female (mean SDS 0.56) than in male patients (mean SDS -0.20; P = .049), and also in individuals with high excreter phenotype (mean SDS 0.44) compared to low excreter patients (mean SDS -0.68; P = .016). In GA1, recommended long-term treatment is effective and allows for normal anthropometric long-term development up to adolescence, with gender- and excreter type-specific variations. Delayed ET and severe movement disorder result in poor anthropometric outcome.

[MOLECULAR-GENETIC ASPECTS OF METHYLMALONIC ACIDURIA DEVELOPMENT (REVIEW)]

The review summarizes the current literature data on the inherited metabolic disorder of branched-chain amino acids - methylmalonic aciduria, characterized by high mortality, acute onset and crisis course. The paper presents the molecular genetic characteristics of the known thirteen different genes (responsible for the synthesis of methylmalonyl-CoA mutase, methylmalonyl-CoA epimerase and vitamin B12 metabolism), mutations of which lead to the development of methylmalonic aciduria. The current knowledge about the potential role of organic acids and their derivatives in the development of metabolic decompensation, toxic damage to the nervous system and internal organs is presented. Early diagnosis by tandem mass spectrometry is extremely important, since timely treatment started (diet therapy, the use of hydroxycobalamin in the B12-dependent form) prevent an unfavorable outcome and allow a high degree of rehabilitation for children with this pathology. Moreover, the identification of the primary molecular genetic defect makes it possible to adjust the patient management tactics and to carry out further prenatal diagnosis of the pathology in subsequent pregnancies.