Urinary Organic Acids Research Articles

A novel mutation in GTPBP3 causes combined oxidative phosphorylation deficiency 23 by affecting pre-mRNA splicing

BackgroundCombined Oxidative Phosphorylation Deficiency 23 (COXPD23) is a rare mitochondrial disease caused by mutations in the GTPBP3 gene. The rare incidence of the disease and the high clinical heterogeneity pose challenges in making a precise diagnosis. Investigations into the rare COXPD23 patients are of pathophysiological and etiological value. In this study, we investigated the genotype-phenotype relationship in a COXPD23 patient from a Manchu family, with GTPBP3 mutations. MethodsRoutine physical examinations, laboratory assays and imaging analyses were performed. The metabolic profiles of amino acids in blood, acylcarnitine in blood and organic acids in urine were used to determine the presence of inherited metabolic diseases. Genetic variations in the family were investigated using whole-exome sequencing and Sanger sequencing. Splicing disruption by a mutation was predicted and verified using a minigene assay. ResultsThe patient presented with severe lactic acidosis, neurological symptoms, multiple symmetrical lesions in the brain and serious mitochondrial energy metabolism disturbances. The c.689A > C (p.Q230P) and c.809-1_809delinsA compound heterozygous mutations were detected in GTPBP3. The novel c.809-1_809delinsA mutation was located at the splicing site of exon 7 and intron 6 and multiple tools predicted that it would disrupt the normal splicing. The minigene assay proved that the novel mutation resulted in two aberrant transcripts that created premature termination codons. ConclusionsThe clinical manifestations, brain imaging change, mitochondrial metabolism disturbances and the detection and validation of the GTPBP3 mutations expand the profile of COXPD23 and the pathogenic mutation spectrum. Our study improves the understanding of the pathophysiology and etiology of COXPD23.

Secondary Carnitine Deficiency in Neonates and Infants Requiring Surgery for Intestinal Obstructions-An Underestimated and Undermanaged Problem.

This study aims to elucidate the relationship between intestinal obstruction and carnitine deficiency in neonates and infants. We retrospectively reviewed medical records of 330 neonates and infants, younger than six months, who underwent surgery for intestinal obstruction at our institute from January 2009 to April 2022. The analysis focused on clinical symptoms, related signs, complications, and etiology of the intestinal obstruction. Tandem mass spectrometry (MS/MS) or urine organic acid analysis was conducted for 47 patients, revealing carnitine deficiency in 16 patients. The incidence of carnitine deficiency was 34.0% in the suspicious group and 4.8% overall, significantly higher than in the general population in Taiwan. Notably, patients with carnitine deficiency experienced prolonged ileus, with a mean fasting duration of 41.7 days (range 7.8-65.5 days), compared to 10.8 days (range 8.2-13.4 days) in patients without carnitine deficiency. Carnitine replacement therapy was administered to twelve patients at dosages ranging from 32 to 90 mg/kg/day. One patient exhibited a drug allergy with skin rashes. Our findings suggest that carnitine deficiency should be considered in cases of neonatal and infant intestinal obstruction. Replacement therapy is straightforward and can be prognostically beneficial for some patients. Therefore, we recommend generalizing MS/MS and urine organic acid analysis, particularly for patients with prolonged ileus.

Investigation of Urine Organic Acid Profile in Coronavirus Disease (COVID-19) Patients.

Coronavirus disease 2019 (COVID-19) is a viral infection caused by severe acute respiratory syn-drome coronavirus 2 (SARS-CoV-2). The high mortality and morbidity rate and its course with a wide variety of clinical symptoms indicate that the disease affects many metabolic pathways. The aim of our study was to investi-gate the metabolic effects of SARS-CoV-2 by evaluating the urinary organic acid profile in patients with SARS-CoV-2 infection. Can metabolites in urine guide the diagnosis, follow-up, treatment, and prognosis of COVID-19? Forty-two patients, including 30 SARS-CoV-2 RT-PCR positive patients and 12 SARS-CoV-2 RT-PCR negative controls, were studied. SARS-COV-2 RT-PCR of nasopharyngeal swab samples was studied. Urines were evaluated in the GCMS-QP2010 SE Gas Chromatograph Mass Spectrometer (SHIMADZU) device for organic acid profile in the metabolism laboratory. Urine organic acid profile was evaluated by studying 117 organic acids in each patient. Tiglylglycine, 2-hydroxybutyric acid, 4-hydroxyphenylpyruvic acid, 3-hydroxypropionic acid, erythro-4,5-dihydroxyhexanoic acid lactone, 2-hydroxyphenylacetic acid, N-acetyltyrosine, 3-phenyllactic acid, 5-hydroxyindolacetic acid, 3-hydroxysebacic acid, palmitic acid, 3-methylglutaconic acid, 3-methylglutaric acid, lactic acid, pyruvic acid-oxime, 3-hydroxysobutyric acid, and organic acids were found to be increased, compared to the control group. Tiglylglycine has been specifically identified as a potential biomarker of respiratory chain disorders. The deterioration in lipid metabolism and pyruvate pathway in COVID-19 patients was evaluated as remarkable.

Result of a Pilot External Quality Assessment Scheme for Clinical Diagnosis of Inherited Metabolic Disorders in China.

We aimed to evaluate the diagnostic capabilities of Chinese laboratories for inherited metabolic disorders (IMDs) using gas chromatography-mass spectrometry (GC-MS) on urine samples. Meanwhile, based on the result of the pilot external quality assessment (EQA) scheme, we hope to establish a standardized and reliable procedure for future EQA practice. We recruited laboratories that participated in the EQA of quantitative analysis of urinary organic acids with GC-MS before joining the surveys. In each survey, a set of five real urine samples was distributed to each participant. The participants should analyze the sample by GC-MS and report the "analytical result", "the most likely diagnosis", and "recommendation for further tests" to the NCCL before the deadline. A total of 21 laboratories participated in the scheme. The pass rates were 94.4% in 2020 and 89.5% in 2021. For all eight IMDs tested, the analytical proficiency rates ranged from 84.7% - 100%, and the interpretational performance rate ranged from 88.2% - 97.0%. The performance on hyperphenylalaninemia (HPA), 3-methylcrotonyl-CoA carboxylase deficiency (MCCD), and ethylmalonic encephalopathy (EE) samples were not satisfactory. In general, the participants of this pilot EQA scheme are equipped with the basic capability for qualitative organic acid analysis and interpretation of the results. Limited by the small size of laboratories and samples involved, this activity could not fully reflect the state of clinical practice of Chinese laboratories. NCCL will improve the EQA scheme and implement more EQA activities in the future.

Prevalence and outcome of inborn errors of metabolism among high-risk neonates: an Egyptian single-center study

Background Inborn errors of metabolism (IEM) are genetic disorders caused by incompetence in enzymatic reactions of intermediary metabolism due to an insufficient amount or unstable form of the involved enzyme. Aim To assess the prevalence and outcome of IEM among high-risk neonates for early diagnosis and detection of treatable causes to minimize morbidity and mortality rate in neonates. Methods This cross-sectional study was carried out on 684 neonates at the Neonatal Intensive Care Unit in the Pediatrics Department at Zagazig University Children’s Hospital from February 2020 to February 2023. Extended metabolic screen (EMS) was done for full-term neonates and preterm of more than 32 weeks of gestation. Further investigations such as plasma ammonia, plasma lactate, urine organic acid analysis, blood gas, serum anion gap, and the blood glucose level were also measured. Results The prevalence of IEM was 4.4%. The most common presentations among the cases of IEM were not doing well, respiratory distress, encephalopathy, and convulsion. As regards provisional diagnosis, 11 cases were diagnosed as maple syrup urine disease, 5 cases with glycine encephalopathy, 5 cases with medium-chain acyl CoA dehydrogenase deficiency,4 cases with methylmalonic acidemia, 2 cases with isovaleric acidemia, 2 cases with citrullinemia type 1, and one case with propionic academia; 12 (40%) of IEM cases died. Conclusion IEM disorders are not rare diseases in high-risk neonates with attention to consanguinity, which is a common tradition in our country. The delay in diagnosis of IEM leads to high morbidity and mortality.

Clinical and Molecular Genetic Analysis with Methylmalonic Acidemia Combined with Homocystinuria.

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. 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. 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). 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.

Selective Screening for Inborn Errors of Metabolism Using Tandem Mass Spectrometry in Newborns of the West Kazakhstan: Pilot Study

Tandem mass spectrometry can detect and quantify many metabolites in a single blood spot to diagnose amino acid disorders, organic acids, fatty acid oxidation, and urea cycle disorders. The use of tandem mass spectrometry (MS/MS) is expanding for the implementation of newborn screening programs for inborn errors of metabolism and for selective screening of children of different ages. In Kazakhstan, the use of MS/MS in metabolic screening programs is not yet developed due to the high cost of equipment and consumables and the lack of special screening centers and specialists. Data on the prevalence of most inborn errors of metabolism in Kazakhstan are not presented in the literature. Aim: to perform selective screening for hereditary metabolic diseases among newborns in western Kazakhstan using the liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Methods: Selective screening was performed among 250 newborns with suspected hereditary metabolic disorders using tandem mass spectrometry. Results: The results of selective newborn screening were interpreted by comparison with reference values established for this group. Diagnosis was based on clinical signs, blood levels of amino acids, acylcarnitines, succinylacetone, urine organic acids, and gene mutation tests. An assessment of 37 inborn errors of metabolism frequencies in high-risk newborns was performed. Conclusion: The research will further develop the national as selective as expanded newborn screening programs.

A new adsorptive 3D–printed sampling device for simultaneous determination of 63 urinary organic acids by LC–MS/MS

BackgroundThe detection and quantification of urinary metabolites play an important role in disease diagnosis. In most cases, urinary analyses are done with liquid urine samples, which must be quickly transported to the laboratory to avoid metabolites degradation that is associated with temperature fluctuations. Consequently, dried sampling devices have emerged to minimize analyte degradation. However, most commercial dried sampling devices are expensive, aggregate low volumes, and need better analytical sensitivity. Therefore, a new dry urine sampling device that is inexpensive, suitable for domestic sampling operation, and efficient for quantifying metabolites without requiring high–resolution instruments is proposed in the present study. ResultsThe newly designed dry urine sampling device was produced by 3D printing that efficiently determines 63 urinary organic acids using liquid chromatography coupled with mass spectrometry (LC–MS/MS). The system's efficiency was demonstrated with analytical figures of merit, such as precision, accuracy, and stability of analytes after the sampling and storing of ordinary urine samples. The limits of quantification ranged from 0.01 to 0.42 ng mL–1. Precision and accuracy tests showed relative standard deviations of less than 15 %. The urine stability in the sampling device was high within seven days without any significant degradation of the metabolites. The method was applied to the analysis of 10 human urine samples and compared to a conventional method without the use of the sampling device. The results showed no statistically significant differences, demonstrating the method's efficiency. SignificanceThe proposed 3–D printing device was developed with fast, low–cost manufacturing features and can be manufactured with different volumetric capacities, adaptable to the needs of each user. Furthermore, it is innovative because this is the first sampling device that is effective for the simultaneous storage and preservation of several important urinary metabolites. Thus, it is anticipated that its application would contribute significantly to the identification of metabolic disorders.

Analysis of disease spectrum for abnormal 3-hydroxyisovalerylcarnitine metabolism identified through newborn screening and clinical diagnosis

To explore the disease spectrum for abnormal 3-hydroxyisovalerylcarnitine (C5OH) metabolism identified through newborn screening and clinical diagnosis patients and the key points for differential diagnosis so as to raise the awareness of pediatricians for such diseases. Clinical data of 85 neonates with abnormal C5OH metabolism identified from February 2004 to January 2022 at Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were collected. Their clinical manifestations and results of tandem mass spectrometry (MS/MS), gas chromatography mass spectrometry (GC-MS) and genetic testing were retrospectively analyzed. Among the 85 cases, 46 (54.1%) were identified by neonate screening, whilst 39 (45.9%) were clinically diagnosed patients. Five diseases were diagnosed, including 28 cases with multiple carboxylase deficiency (MCD, 32.9%), 29 cases with 3-methylcrotonyl-coenzymeAcarboxylasedeficiency (MCCD, 34.1%), 4 cases with 3-methylglutaconic acid (3-MGA, 4.7%), 7 cases with 3-hydroxy-3-methylglutaric acid (3-HMG, 8.2%), and 17 cases with beta-ketothiolase deficiency (BKD, 20.0%). The disorders were characterized by sudden onset, anorexia, vomiting, diarrhea, abnormal breathing, consciousness disorder, spasm and developmental delay. Among newborns with abnormal C5OH metabolism, MCCD is the most common disorder, which was followed by BKD and MCD. For patients with abnormal C5OH metabolism, MCD is the most common, followed by BKD and 3-HMG. C5OH related diseases have great heterogeneity. Combination of blood acylcarnitine levels, urinary organic acid levels and genetic testing based on clinical characteristics can help to attain the diagnosis.

Congenital neuroblastoma presenting as profound neonatal metabolic acidosis with systemic hypertension: Case report.

Clinical collapse in the newborn most often occurs secondary to sepsis, delivery complications, congenital cardiac defects, or inborn errors of metabolism. We report on a neonate with respiratory, cardiac, and hepatic failure, with disproportionate metabolic acidosis and systemic hypertension, found to be caused by a congenital neuroblastoma. A term infant presented to our Level IV NICU via emergent transport at 12 hours of life with clinical and laboratory findings consistent with respiratory, cardiac, and hepatic failure. Typical workup for sepsis and cardiac etiology was unrevealing. The infant was noted to have systemic hypertension despite prolonged capillary refill. A profound metabolic acidosis led the primary team to pursue a genetics consult. In the course of the workup for disorders of metabolism, a urine organic acids panel revealed an elevated HVA (homovanillic acid) and VMA (vanillylmandelic acid), the metabolites of the neurotransmitters epinephrine, norepinephrine and dopamine. Subsequent abdominal ultrasound and chest/abdomen CT revealed a large heterogeneous mass with internal vascular flow and scattered calcifications arising from the medial limb of the left adrenal gland, consistent with neuroblastoma. Although rare, neuroblastomas can present clinically in the perinatal period in a manner requiring immediate life-saving intervention. Providers should consider the diagnosis in the setting of a newborn with a sepsis-like syndrome or profound metabolic acidosis presenting along with systemic hypertension without clear underlying etiology.

A-318 Pseudo-hypertriglyceridemia in a 2-year-old Male with Global Developmental Delay, Myopathy and Adrenal Hypoplasia

Abstract Background Pseudo-hypertriglyceridemia is an overestimation of serum triglyceride levels due to laboratory assays that measure free glycerol concentrations instead of triglycerides directly. Consequently, conditions presenting with elevated levels of endogenous or exogenous free glycerol, such as glycerol kinase deficiency, result in an overestimation of serum triglycerides. Glycerol kinase deficiency (GKD) is caused by pathogenic variants of the GK gene on chromosome Xp21. Three forms of GKD are recognized, characterized as infantile, juvenile, and adult forms. While the juvenile and adult forms are recognized as isolated GKD, the infantile form manifests itself as part of the Xp21.3 contiguous gene deletion syndrome, also known as complex GKD. This syndrome is composed of genes associated with Duchenne muscular dystrophy (DMD), X-linked congenital adrenal hypoplasia (NR0B1), and intellectual disability (IL1RAPL1). GKD is characterized biochemically by hyperglycerolaemia and glyceroluria. Case Description A 2-year-old male presented to the genetics clinic with a history of global developmental delay (gross motor and speech), axial hypotonia, poor head control and inability to sit unassisted or walk. Significant findings on examination included a startled appearance, absent eyebrows and temporal thinning, high forehead, frontal bossing, axial hypotonia and peripheral hypertonia. Laboratory findings included elevated creatine kinase (CK) of 14809 units/L (normal 27–160 units/L), aspartate aminotransferase (AST) of 307 (normal 20–60 units/L), alanine aminotransferase (ALT) 265 (normal 15–45 units/L), Adrenocorticotropic Hormone (ACTH) 156 (normal 6–48 pg/mL), and elevated triglycerides at 683 (normal 44–157 mg/dL). There was also a family history of developmental delay and intellectual disability in patient's mother and younger sister. Method Triglycerides are commonly measured indirectly with different enzyme reagents. The Triglycerides in this boy were measured by an automated chemistry analyzer based on a colorimetric serial enzymatic reaction including lipase, glycerol kinase and L-α-glycerol-phosphate oxidase1. Urinary organic acids profile including glycerol was extracted from acidified urine (pH 1-2) using diethyl ether. Organic extracts are then evaporated to dryness under nitrogen and trimethysilyl derivatized by the addition of N, O-bis (trimethylsilyl) trifluoroacetamide with 1% trimethylchorosilane (BSTFA/TMCS) and analyzed by gas chromatography-mass spectrometry (GC-MS). Results A comprehensive work-up including qualitative urinary organic acid analysis and chromosomal microarray was carried out. Urinary organic acids analysis revealed very abnormal accumulation of glycerol. Chromosomal microarray results showed a 4.2 Mb deletion of Xp21.3p21.1 (29296579-33551038) including complete copies of GK, DMD, and NR0B1 genes as well as multiple exons of IL1RAPL1. This confirmed his GKD as part of the Xp21 continuous gene deletion syndrome. Elevated triglycerides were then recognized as pseudo-hypertriglyceridemia after the diagnosis. Mild glyceroluria is also observed in the younger sister of this patient. Discussion and Conclusion This case highlights the importance recognizing pseudo-hypertriglyceridemia and diagnostic challenges. Earlier identification through urine organic acid analysis could have been made. The combination of clinical presentations and increased glycerol should cause suspicion for GKD. Female carriers of this X-linked disorder need to be evaluated for intellectual disability, as seen in this patient's mother and younger sister.

B-201 Development of a Quantitative Gas Chromatography Tandem Mass Spectrometry Method for Metabolic Profiling of Urine Organic Acids

Abstract Background Urine organic acids (UOA) analysis is an essential investigation for inborn errors of metabolism (IEMs). The vast majority of methods use gas chromatography mass spectrometry (GC-MS) and are only qualitative. Gas chromatography tandem mass spectrometry (GC-MS/MS) offers greater sensitivity and selectivity, and enables the combination of qualitative screening with quantitative analysis. We describe the development and preliminary validation results of a quantitative GC-MS/MS method. Methods Urine creatinine concentrations were measured (CobasPro, Roche Diagnostics) and normalized to 1.25 mmol/L. After internal standard addition, each urine specimen, calibration standard and QC were incubated with a hydroxylamine solution followed by a liquid-liquid extraction. Further sample concentration permitted the isolated UOA to be derivatized using N,O-bis(trimethylsilyl)trifluoroacetamine (BSTFA) with 1% chlorotrimethylsilane (TMCS) prior to injection. GC-MS/MS analysis was performed using a GC-MS-TQ8050 triple quadrupole system (Shimadzu) with a 30 m DB-5MS (Agilent J&W) capillary column (0.25 mm, ID of 0.25 µm). Split injection mode was deployed with an initial column temperature of 70°C. The mass spectrometer was operated in electron ionization (EI) and multiple reaction monitoring (MRM) modes. The linear concentration ranges of the targeted metabolites within the devised GC-MS/MS protocol were determined. Results The optimal temperature gradient for high-resolution UOA separations was derived and their respective retention times determined. MS/MS detection parameters were optimized to permit the identification of precursor and production ions for all (N = 38) derivatized UOA. Total analysis time was 33.8 min per injection. The achieved linear concentration ranges for each metabolite was respectively determined. Linear concentration ranges and correlation coefficients of representative UOA: 3-hydroxyisovaleric acid (range = 9 to 708 µmol/L, R2 = 0.9874); lactic acid (range = 15 to 751 µmol/L, R2 = 0.9936); 3-hydroxybutyric acid (range = 15 to 751 µmol/L, R2 = 0.9991); and 2-methyl-3-hydroxybutyric acid (range = 10 to 501 µmol/L, R2 = 0.9996). The correlation coefficients for all remaining UOA ranged from R2 = 0.9458 (4-hydroxyphenylpyruvic acid) to R2 = 0.9998 (3-methylglutanoic acid and ethylmalonic acid). Conclusion The devised GC-MS/MS protocol permits the unbiased identification and quantification of UOA used to investigate IEMs. The linear concentration ranges for all analytes were determined and are appropriate for monitoring these markers of inherited enzyme deficiencies. The analytical performance of this UOA GC-MS/MS method must be further validated and its diagnostic performance for selected IEMs characterized.

Sequence variants in the BTD underlying biotinidase deficiency in families of Pakistani origin.

Biotinidase deficiency (BTD) is a rare autosomal recessive metabolic disease, which develops neurological symptoms because of the impaired biotin recycling. Pathogenic mutations on BTD gene cause BTD deficiency. The clinical features and mutation analysis of Pakistani children with BTD deficiency have rarely been described. Herein, for the first time, we report the clinical features, BTD gene mutations and biochemical analysis of seven symptomatic children with BTD deficiency from Pakistan. Seven suspected BTD-deficient patients who presented abnormal organic acid profiles and clinical features were subjected to Sanger sequencing to identify pathogenic mutations in the BTD gene. The results were analyzed by Mutation Surveyor Software. All seven patients exhibited common biotinidase deficiency symptoms including hypotonia, developmental delay and seizures. Biochemical analysis shows marked excretion of 3-hydroxy isovalerate in all cases, followed by 3-hydroxy propionate and methyl citrate. Sanger sequencing revealed one frame-shift mutation, c.98_104delinsTCC (p.Cys33Phefs), and two missense mutations, c.1612C>A (p.Arg538Ser) and c.1330G>C (p.Asp444His). All mutations were in the homozygous state and classified as pathogenic in published studies and mutation databases. This study has validated the BTD variants as the underlying cause of biotinidase deficiency in which molecular testing of BTD is supported by urinary organic acid analysis and clinical diagnosis. Secondly, the strength of the local availability of this test in Pakistan will paved the way for the neonatal screening of biotinidase deficiency.

Use of sodium D, L-3-hydroxybutyrate as adjunct therapy in two siblings with HMG-CoA lyase deficiency

3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase deficiency is a rare autosomal recessive mitochondrial disease characterised by recurrent life-threatening metabolic crises generally presenting in neonates or infancy during catabolic stress triggered by prolonged fasting or intercurrent illness. Acute decompensations with lethargy, vomiting, hypoketotic hypoglycemia and metabolic acidosis may evolve into Reye-like syndrome if untreated, with acute liver failure, hyperammonemic encephalopathy, dilated cardiomyopathy, and death in 20% of cases. Long-term health complications include psychomotor retardation, white matter abnormalities, epilepsy, hepatic steatosis, pancreatitis, cardiomyopathy, and arrythmia. The mitochondrial enzyme catalyses the cleavage of HMG-CoA to acetyl-CoA and acetoacetate, the common final step of ketogenesis and leucine degradation, resulting in diagnostic urinary organic acid pattern (elevated 3-hydroxy-3-methylglutaric, 3-methylgutaconic, 3-methylglutaric, and 3-hydroxyisovaleric acids) with the absence of ketonuria, when deficient. Therapeutic interventions include dietary protein or leucine and fat restriction, carnitine supplementation, avoidance of fasting, and use of carbohydrate-based high caloric intake when unwell. We describe the clinical course and diagnostic work-up in two affected siblings, with the proband presenting with severe neonatal onset disease with metabolic acidosis, non-ketotic hypoglycaemia, hyperammonemia and white matter changes on brain MRI. High-risk screening for a younger sibling led to pre-emptive management with good outcomes. Sodium D, L-3-hydroxybutyrate (S-DL-3OHB) was used in both siblings as an adjunct therapy to prevent cerebral dysfunction and cardiomyopathy, with the rationale that decreased ketogenesis in this disorder may impact the major energy source for the brain and heart during starvation. S-DL-3OHB therapy is a well-tolerated and effective therapeutic option for this disorder.

Clinical, radiological, biochemical and molecular characterization of a new case with multiple mitochondrial dysfunction syndrome due to IBA57: Lysine and tryptophan metabolites as potential biomarkers

Iron‑sulfur clusters (FeS) are one of the most primitive and ubiquitous cofactors used by various enzymes in multiple pathways. Biosynthesis of FeS is a complex multi-step process that is tightly regulated and requires multiple machineries. IBA57, along with ISCA1 and ISCA2, play a role in maturation of [4Fe-4S] clusters which are required for multiple mitochondrial enzymes including mitochondrial Complex I, Complex II, lipoic acid synthase, and aconitase. Pathogenic variants in IBA57 have been associated with multiple mitochondrial dysfunctions syndrome 3 (MMDS3) characterized by infantile to early childhood-onset psychomotor regression, optic atrophy and nonspecific dysmorphism. Here we report a female proband who had prenatal involvement including IUGR and microcephaly and developed subacute psychomotor regression at the age of 5 weeks in the setting of preceding viral infection. Brain imaging revealed cortical malformation with polymicrogyria and abnormal signal alteration in brainstem and spinal cord. Biochemical analysis revealed increased plasma glycine and hyperexcretion of multiple organic acids in urine, raising the concern for lipoic acid biosynthesis defects and mitochondrial FeS assembly defects. Molecular analysis subsequently detected compound heterozygous variants in IBA57, confirming the diagnosis of MMDS3. Although the number of MMDS3 patients are limited, certain degree of genotype-phenotype correlation has been observed. Unusual brain imaging in the proband highlights the need to include mitochondrial disorders as differential diagnoses of structural brain abnormalities. Lastly, in addition to previously known biomarkers including high blood lactate and plasma glycine levels, the increase of 2-hydroxyadipic and 2-ketoadipic acids in urine organic acid analysis, in the appropriate clinical context, should prompt an evaluation for the lipoic acid biosynthesis defects and mitochondrial FeS assembly defects.

ADCY5-related dyskinesia: a treatable inherited neurometabolic disorder

Case Report. A 40-year-old Brazilian man presented with long-standing loss of balance, dystonia, and choreoathetosis, with episodic paroxysmal worsening. Neuroimaging and cerebrospinal fluid analysis were both unremarkable. Quantitative urine organic acid analysis, plasma acylcarnitine quantitative profile, and quantitative analysis of plasma amino acids by high performance liquid chromatography were all within normal interval values. Multigene next-generation sequencing panel identified the heterozygous pathogenic variant c.1252C>T (p.Arg418Trp) in the ADCY5 gene, defining a diagnosis of ADCY5-related dyskinesia. Oral caffeine was associated to clonazepam and provided marked improvement of motor symptoms. Conclusion. This report adds evidence to the safety and efficacy of caffeine in the treatment of genetically confirmed cases of ADCY5-related dyskinesia in the context of gain-of-function variants.

Clinical Features and Laboratory Diagnosis of Aminoacidopathies: A Narrative Review

Context: There are severe and rare groups of genetic disorders due to defects in metabolic pathways, and they are generally called inborn errors of metabolism. Amino acids, as the building blocks of proteins, have many important structural and functional roles in the human body. The deficiencies of functional enzymes cause defects in metabolic pathways and lead to aminoacidopathies. The diagnosis of aminoacidopathies is challenging for most physicians, as they can present with multiple overlapping symptoms. Evidence Acquisition: PubMed, Cochrane, Embase, and CINAHL were searched with MeSH terms: ‘inborn errors of metabolism' OR ‘Metabolism, Inborn Errors' (MeSH) AND ‘Humans' (MeSH) AND 'Amino Acids/therapeutic use'(MeSH) AND ‘Newborn, Child' (MeSH) OR ‘child' OR ‘newborn' AND "Neonatal Screening"(MeSH). Results: This study summarized some important issues, including clinical and laboratory diagnoses of phenylketonuria, tyrosinemia, methionine, homocysteine and cysteine, sulfite oxidase deficiency, molybdenum cofactor deficiency, tryptophan, glycine, hyperoxaluria, creatine deficiency disorders, serine, proline, glutamine, and urea cycle defect. Conclusions: The prognosis of many metabolic disorders has improved due to recent advances in diagnosis and treatment. The biochemical knowledge of clinicians should be improved to comprehend metabolic disorders. As the diagnostic methods are based on organic acids in urine and acylcarnitine profile, it is necessary to enhance biochemistry knowledge to understand the logic.

Maleic acid is a biomarker for maleylacetoacetate isomerase deficiency; implications for newborn screening of tyrosinemia type 1.

Dried blood spot succinylacetone (SA) is often used as a biomarker for newborn screening (NBS) for tyrosinemia type 1 (TT1). However, false-positive SA results are often observed. Elevated SA may also be due to maleylacetoacetate isomerase deficiency (MAAI-D), which appears to be clinically insignificant. This study investigated whether urine organic acid (uOA) and quantitative urine maleic acid (Q-uMA) analyses can distinguish between TT1 and MAAI-D. We reevaluated/measured uOA (GC-MS) and/or Q-uMA (LC-MS/MS) in available urine samples of nine referred newborns (2 TT1, 7 false-positive), eight genetically confirmed MAAI-D children, and 66 controls. Maleic acid was elevated in uOA of 5/7 false-positive newborns and in the three available samples of confirmed MAAI-D children, but not in TT1 patients. Q-uMA ranged from not detectable to 1.16 mmol/mol creatinine in controls (n = 66) and from 0.95 to 192.06 mmol/mol creatinine in false-positive newborns and MAAI-D children (n = 10). MAAI-D was genetically confirmed in 4/7 false-positive newborns, all with elevated Q-uMA, and rejected in the two newborns with normal Q-uMA. No sample was available for genetic analysis of the last false-positive infant with elevated Q-uMA. Our study shows that MAAI-D is a recognizable cause of false-positive TT1 NBS results. Elevated urine maleic acid excretion seems highly effective in discriminating MAAI-D from TT1.

Miniaturization and Automation Protocol of a Urinary Organic Acid Liquid-Liquid Extraction Method on GC-MS.

The aim of this study was to improve the extraction method for urinary organic acids by miniaturizing and automating the process. Currently, manual extraction methods are commonly used, which can be time-consuming and lead to variations in test results. To address these issues, we reassessed and miniaturized the in-house extraction method, reducing the number of steps and the sample-to-solvent volumes required. The evaluated miniaturized method was translated into an automated extraction procedure on a MicroLab (ML) Star (Hamilton Technologies) liquid handler. This was then validated using samples obtained from the ERNDIM External Quality Assurance program. The organic acid extraction method was successfully miniaturized and automated using the Autosampler robot. The linear range for most of the thirteen standard analytes fell between 0 to 300 mg/L in spiked synthetic urine, with low (50 mg/L), medium (100 mg/L), and high (500 mg/L) levels. The correlation coefficient (r) for most analytes was >0.99, indicating a strong relationship between the measured values. Furthermore, the automated extraction method demonstrated acceptable precision, as most organic acids had coefficients of variation (CVs) below 20%. In conclusion, the automated extraction method provided comparable or even superior results compared to the current in-house method. It has the potential to reduce solvent volumes used during extraction, increase sample throughput, and minimize variability and random errors in routine diagnostic settings.

Biochemical characterization of patients with dihydrolipoamide dehydrogenase deficiency.

Dihydrolipoamide dehydrogenase (DLD; E3) oxidizes lipoic acid. Restoring the oxidized state allows lipoic acid to act as a necessary electron sink for the four mitochondrial keto-acid dehydrogenases: pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, branched-chain α-keto-acid dehydrogenase, and 2-oxoadipate dehydrogenase. DLD deficiency (DLDD) is caused by biallelic pathogenic variants in DLD. Three major forms have been described: encephalopathic, hepatic, and myopathic, although DLDD patients exhibit overlapping phenotypes. Hyperlactatemia, hyperexcretion of tricarboxylic acid cycle (TCA) metabolites and branched-chain keto acids, increased plasma branched-chain amino acids and allo-isoleucine are intermittent metabolic abnormalities reported in patients with DLDD. However, the diagnostic performance of these metabolites has never been studied. Therefore, we sought to systematically evaluate the diagnostic utility of these biomarkers for DLDD. We retrospectively analyzed the results of biochemical testing of six unrelated DLDD patients, including values obtained during both well visits and acute decompensation episodes. Elevation of branched-chain amino acid concentrations was not consistently observed. We found that five of six patients in our cohort had a maximum lifetime value of allo-isoleucine of 6 μmol/L, showing that alloisoleucine elevations even during illness may be subtle. Urine organic acid analysis (UOA) during acute decompensation episodes was abnormal in all cases; however, the pattern of abnormalities had high intersubject variability. No single biomarker was universally present, even in patients experiencing metabolic decompensation. We also observed novel biochemical associations: three patients had hyperexcretion of TCA cycle metabolites during crisis; in two patients, 2-ketoadipic and 2-hydroxyadipic acids, by products of lysine degradation, were detected. We propose that these result from 2-oxoadipate dehydrogenase deficiency, an underappreciated biochemical abnormality in DLD. Given the diversity of biochemical profiles among the patients with DLDD, we conclude that accurate biochemical diagnosis relies on a high index of suspicion and multipronged biochemical analysis, including both plasma amino acid and urine organic acid quantitation during decompensation. Biochemical diagnosis during the well state is challenging. We emphasize the critical importance of multiple simultaneous biochemical tests for diagnosis and monitoring of DLDD. We also highlight the under-recognized role of DLD in the lysine degradation pathway. Larger cohorts of patients are needed to establish a correlation between the biochemical pattern and clinical outcomes, as well as a genotype-phenotype correlation.