Currently, tandem mass spectrometry-based newborn screening (NBS), which examines targeted biomarkers, is the first approach used for the early detection of maple syrup urine disease (MSUD) in newborns, followed by confirmatory genetic mutation tests. However, these diagnostic approaches have limitations, demanding the development of additional tools for the diagnosis/screening of MUSD. Recently, untargeted metabolomics has been used to explore metabolic profiling and discover the potential biomarkers/pathways of inherited metabolic diseases. Thus, we aimed to discover a distinctive metabolic profile and biomarkers/pathways for MSUD newborns using untargeted metabolomics. Herein, untargeted metabolomics was used to analyze dried blood spot (DBS) samples from 22 MSUD and 22 healthy control newborns. Our data identified 210 altered endogenous metabolites in MSUD newborns and new potential MSUD biomarkers, particularly L-alloisoleucine, methionine, and lysoPI. In addition, the most impacted pathways in MSUD newborns were the ascorbate and aldarate pathways and pentose and glucuronate interconversions, suggesting that oxidative and detoxification events may occur in early life. Our approach leads to the identification of new potential biomarkers/pathways that could be used for the early diagnosis/screening of MSUD newborns but require further validation studies. Our untargeted metabolomics findings have undoubtedly added new insights to our understanding of the pathogenicity of MSUD, which helps us select the appropriate early treatments for better health outcomes.

As the diagnosis and treatment of patients with inborn errors of metabolism has improved dramatically over the years, more people with these conditions are surviving into child-bearing years. Given the changes in metabolism throughout pregnancy, this time presents a unique challenge in their care. Overall metabolic shifts in pregnancy go from anabolism to catabolism driven by endocrinologic changes, along with changes in rates of gluconeogenesis, glucose consumption, amino acid transport, protein consumption, and lipid breakdown, result in a complicated metabolic picture. Additionally, maternal inborn errors of metabolism can affect a fetus, as in phenylketonuria, and fetal inborn errors of metabolism can affect the mother, as in certain fatty acid oxidation disorders. Data on these conditions is often very limited. A summary of the current literature, risks associated with pregnancy in inborn errors of metabolism, and suggestions for management of these conditions will be presented.

BACKGROUND: Maple Syrup Urine Disease (MSUD) is an autosomal recessive metabolic disorder originating from defects in the branched-chain α-ketoacid dehydrogenase (BCKDH) complex encoded by BCKDHA, BCKDHB, and DBT. This condition presents a spectrum of symptoms and potentially fatal outcomes. Although numerous mutations in the BCKDH complex genes associated with MSUD have been identified, the relationship between specific genotypes remains to be fully elucidated.
OBJECTIVE: Our objective was to predict the pathogenicity of these genetic mutations and establish potential links between genotypic alterations and the clinical phenotypes of MSUD.
METHODS: Retrospective population-based cohort.
METHODS: We analyzed 20 MSUD patients from the Children\'s Hospital at Zhejiang University School of Medicine (Hangzhou, China), recorded from January 2010 to May 2023. Patients\' blood samples were collected by heel-stick through neonatal screening, and amino acid profiles were measured by tandem mass spectrometry. In silico methods were employed to assess the pathogenicity, stability, and biophysical properties. Various computation tools were utilized for assessment, namely PredictSNP, MAGPIE, iStable, Align GVGD, ConSurf and SNP effect.
RESULTS: We detected 25 distinct mutations, including 12 novel mutations. The BCKDHB gene was the most commonly affected (53.3%) compared to the BCKDHA gene (20.0%) and DBT gene (26.7%). In silico webservers predicted all novel mutations were disease-causing.
CONCLUSIONS: This study highlights the genetic complexity of MSUD and underscores the importance of early detection and intervention. Integrating neonatal screening with advanced sequencing methodologies is pivotal in ensuring precise diagnosis and effective management of MSUD, thereby significantly improving the prognosis for individuals afflicted with this condition.

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

Significant progress has been achieved in enhancing early outcomes for individuals with maple syrup urine disease (MSUD), a rare metabolic disorder that leads to the accumulation of branched-chain amino acids leucine, isoleucine, and valine, where leucine is known as the primary neurotoxic metabolite. Newborn screening is helpful in early diagnosis and implementation of dietary treatment, thus reducing neurological deterioration and complications in young children. However, patients face the life-long challenge of maintaining metabolic control through adherence to a strict low-leucine diet to avoid long-term consequences of chronic hyperleucinemia, which include cognitive deficits, mood disorders, and movement disorders. This case report exemplifies the complex involvement of MSUD in adult survivors. Despite presenting early in life, the patient thrived until the onset of psychiatric symptoms. The subject of this case is a 25-year-old woman with MSUD, who remained in her usual state of health until presentation to the emergency department (ED) with psychosis and altered mental status. However, due to a lack of medical records and poor communication, there was a delay in considering MSUD as a primary cause of her psychiatric symptoms. Although a genetics consultation was later arranged and efforts were made to decrease plasma leucine to the therapeutic range, these interventions proved inadequate in halting her deterioration in health. Her condition worsened within 72 h, culminating in her untimely death. This case emphasizes the comorbidity of psychiatric involvement in MSUD, which contributes to metabolic decompensation that can lead to cerebral edema and death. This case also highlights the pressing need for enhanced strategies for the acute management and long-term care of MSUD patients with psychiatric involvement, particularly in scenarios where mental disturbance could lead to noncompliance.

OBJECTIVE: The literature about oral manifestations and dental management in maple syrup urine disease (MSUD) is sparse. The aim of this report is to present a new case of MSUD with special emphasis on oral findings and to review the relevant literature.
METHODS: A case report of a 4-year-old boy with MSUD was described according to the CARE guidelines for describing case reports. Scoping review of relevant literature was performed, according to the PRISMA-ScR guidelines, by searching PubMed, Medline, Embase, and the grey literature for articles describing dental management and/or oral manifestations in MSUD.
RESULTS: The initial search identified 219 articles, but only 4 met the inclusion criteria. Rampant caries and plaque induced gingivitis were the main oro-dental findings in MSUD. Other oral findings included enamel hypoplasia, skeletal abnormalities, and abnormal oral behaviors. Disease-related factors appeared to play a major role in the development of the observed oral phenotype.
CONCLUSIONS: Oral health in MSUD seems to be influenced by the reliance on semi-synthetic diet and associated neurocognitive complications. Tailored oral health promotional interventions should be included in the multidisciplinary management of patients with MSUD.

Strict adherence to a diet is an essential pillar of long-term treatment for many inborn errors of metabolism (IEMs). Tools that educate patients about dietary management can positively condition adherence and prevent morbidity. We designed a free online dietary calculation program (Odimet®, version 2.1.) for IEMs patients in 2008, updated in 2022, that provides detailed information on the content of amino acids, protein, lipids, carbohydrates, vitamins and minerals in >3000 food products, including specific medical foods for IEM. We analyzed the statistics on visits to Odimet® to evaluate its usefulness for long-term dietary management during a 5-year period focusing on three periods: pre-pandemic (15 March 2018-14 March 2020); pandemic 1 (15 March 2020-14 March 2021); and pandemic 2 period (15 March 2021-15 March 2023), in 120 patients with the following distribution: 84 patients with phenylketonuria (PKU); 12 with maple syrup urine disease (MSUD); 11 with urea cycle disorders (UCDs); and 13 with classical galactosemia. The evolutionary levels of their specific metabolic markers were evaluated, showing that globally, both pediatric and adult patients maintain a good metabolic control, even during a pandemic (median levels of phenylalanine in pediatric PKU patients 213.4 µmol/L and 482.3 µmol/L in adults; of leucine in MSUD patients: 144.2 µmol/L; of glutamine in UCDs: 726.8 µmol/L; and of galactose 1-phosphate levels in galactosemia: 0.08 µmol/L). The proportion of patients using Odimet® ranges from 78-100%. An increase in the number of diets being calculated was observed during COVID-19 pandemic. Currently, 14,825 products have been introduced (3094 from the general database, and 11,731 added by users to their own profiles). In 2023 63 emergency dietary adjustments in the studied intoxication-type pathologies were calculated in Odimet®. Our results suggest that its regular use contributes to maintaining metabolic stability in IEMs patients, allowing them to adapt their menus to their lifestyle, and represents a powerful complementary tele-health tool which can be used to perform remote real-time dietary follow-up.

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An 11-month-old female infant diagnosed with classic subtype IB maple syrup urine disease underwent living donor liver transplantation. Blood samples for plasma amino acid analysis were collected during the three phases of the operation. Despite the perioperative prophylactic administration of 12.5% hypertonic dextrose solution with insulin and a 20% intralipid emulsion, the blood levels of the branched-chain amino acids increased dramatically during surgery, consistent with an acute intraoperative metabolic decompensation. However, these blood levels normalized soon after liver transplantation with an excellent outcome. We suggest that the occurrence of an intraoperative metabolic crisis during liver transplantation is not necessarily a sign of graft failure.

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