Successful treatment of severe MSUD in Bckdhb-/- mice with neonatal AAV gene therapy.

Maple syrup urine disease (MSUD) is rare autosomal recessive metabolic disorder caused by the dysfunction of the mitochondrial branched-chain 2-ketoacid dehydrogenase (BCKD) enzyme complex leading to massive accumulation of branched-chain amino acids and 2-keto acids. MSUD management, based on a life-long strict protein restriction with nontoxic amino acids oral supplementation represents an unmet need as it is associated with a poor quality of life, and does not fully protect from acute life-threatening decompensations or long-term neuropsychiatric complications. Orthotopic liver transplantation is a beneficial therapeutic option, which shows that restoration of only a fraction of whole-body BCKD enzyme activity is therapeutic. MSUD is thus an ideal target for gene therapy. We and others have tested AAV gene therapy in mice for two of the three genes involved in MSUD, BCKDHA and DBT. In this study, we developed a similar approach for the third MSUD gene, BCKDHB. We performed the first characterization of a Bckdhb-/- mouse model, which recapitulates the severe human phenotype of MSUD with early-neonatal symptoms leading to death during the first week of life with massive accumulation of MSUD biomarkers. Based on our previous experience in Bckdha-/- mice, we designed a transgene carrying the human BCKDHB gene under the control of a ubiquitous EF1α promoter, encapsidated in an AAV8 capsid. Injection in neonatal Bckdhb-/- mice at 1014 vg/kg achieved long-term rescue of the severe MSUD phenotype of Bckdhb-/- mice. These data further validate the efficacy of gene therapy for MSUD opening perspectives towards clinical translation.

Analysis of Branched Amino Acids by UPLC as an Alternative Method for the Management of Patients with MUSD.

BACKGROUND: Maple syrup urine disease (MSUD) is a severe life-threatening metabolic disorder. Patients' poor outcomes could be prevented by early diagnosis and regular monitoring, which mainly depend on the analysis of branched amino acids (BCAAs) in plasma. The study aimed to test whether the analysis of BCAAs by ultra-performance liquid chromatography (UPLC) is an alternative to an analysis by ion-exchange chromatography (IEC) for the diagnosis and monitoring of MSUD. METHODS: The two methods analyzed fifty plasma samples obtained from treated and untreated patients with MSUD. Data were analyzed using Passing-Bablok and Bland-Altman methods. RESULTS: The slope of the regression lines was equal or close to one for the three BCAAs, indicating no significant proportional differences between the two methods. A slight positive or negative bias was found for leucine and alloisoleucine, respectively. However, for each amino acid, one or two measurement pairs were out of statistical interval of agreement. Despite small analytical differences, the two methods could be considered in clinical agreement since the differences have no impact on the diagnosis and management of patients. CONCLUSIONS: UPLC and IEC methods are in clinical agreement for plasma BCAAs analysis. The UPLC method could be used simultaneously or interchangeably with the IEC method for diagnosing and monitoring MSUD patients. However, for reasons of practicability, the alternative method should only be used when the usual method cannot be carried out.

Congenital Hyperinsulinism and Maple Syrup Urine Disease: A Challenging Combination

Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycemia in infancy. CHI is a challenging disease to diagnose and manage. Moreover, complicating the course of the disease with another metabolic disease, in this case maple syrup urine disease (MSUD), adds more challenges to the already complex management. We report a term neonate who developed symptomatic, non-ketotic hypoglycemia with a blood glucose (BG) level of 1.9 mmol/L at 21-hours of life. A critical sample at that time showed high serum insulin and C-peptide levels confirming the diagnosis of CHI. Tandem mass spectrometry done at the same time was suggestive of MSUD which was confirmed by high performance liquid chromatography. The diagnosis of both conditions was subsequently confirmed by molecular genetic testing. His hypoglycemia was managed with high glucose infusion with medical therapy for CHI and branched chain amino acids (BCAA) restricted medical formula. At the age of four months, a near-total pancreatectomy was done, due to the failure of conventional therapy. Throughout his complicated course, he required meticulous monitoring of his BG and modified plasma amino acid profile aiming to maintain the BG at ≥3.9 mmol/L and levels of the three BCAAs at the disease therapeutic targets for his age. The patient is currently 29 months old and has normal growth and development. This patient is perhaps the only known case of the co-occurrence of CHI with MSUD. Both hypoglycemia and leucine encephalopathy can result in death or permanent neurological damage. The management of CHI and MSUD in combination is very challenging.

Neonatal gene therapy achieves sustained disease rescue of maple syrup urine disease in mice.

Maple syrup urine disease (MSUD) is a rare recessively inherited metabolic disorder causing accumulation of branched chain amino acids leading to neonatal death, if untreated. Treatment for MSUD represents an unmet need because the current treatment with life-long low-protein diet is challenging to maintain, and despite treatment the risk of acute decompensations and neuropsychiatric symptoms remains. Here, based on significant liver contribution to the catabolism of the branched chain amino acid leucine, we develop a liver-directed adeno-associated virus (AAV8) gene therapy for MSUD. We establish and characterize the Bckdha (branched chain keto acid dehydrogenase a)-/- mouse that exhibits a lethal neonatal phenotype mimicking human MSUD. Animals were treated at P0 with intravenous human BCKDHA AAV8 vectors under the control of either a ubiquitous or a liver-specific promoter. BCKDHA gene transfer rescued the lethal phenotype. While the use of a ubiquitous promoter fully and sustainably rescued the disease (long-term survival, normal phenotype and correction of biochemical abnormalities), liver-specific expression of BCKDHA led to partial, though sustained rescue. Here we show efficacy of gene therapy for MSUD demonstrating its potential for clinical translation.

Continuous veno-venous hemodiafiltration in neonates with maple syrup urine disease.

INTRODUCTION: Herein, we aimed to discuss our experience in 16 newborn patients with Maple syrup urine disease (MSUD) who were treated with urgent renal replacement therapy (RRT). METHODS: The patients underwent continuous veno-venous hemodiafiltration (CVVHDF) or peritoneal dialysis (PD) as renal replacement therapy. RESULTS: Eleven (68.75%) patients underwent CVVHDF and five (31.25%) underwent peritoneal dialysis. The median leucine reduction rate per hour was 2.56% (1.75-7.6) in the CVVHDF group, 0.78% (0.54-1.83) in the PD group, and was significantly higher in the CVVHDF group (p = 0.001). Posttreatment plasma leucine levels were found to be 198 (20-721) µmol/L in the CVVHDF group and 600 (250-967) µmol/L in the PD group, and CVVHDF was found to be significantly lower (p = 0.08). Complications such as hypotension, electrolyte imbalance, and filter obstruction occurred in the CVVHDF group. CONCLUSION: This study showed that CVVHDF is more effective than PD for rapidly eliminating elevated leucine levels caused by MSUD in the newborn and it is not associated with increased complication rates.

Inborn error of metabolism patients after liver transplantation: Outcomes of 35 patients over 27 years in one pediatric quaternary hospital.

Liver transplantation (LT) has been used for many years as a therapeutic option for certain inborn errors of metabolism (IEMs). Here we present one institution's 27 years of experience with LT in IEMs. Our objective is to assess the outcomes of IEM patients who have undergone LT, which we hypothesize to be generally successful for prevention of metabolic decompensation. A retrospective chart review was performed on patients with urea cycle defects, organic acidemias, and amino acidopathies who underwent LT at the Children's Hospital of Philadelphia. Thirty-five patients with the following conditions have undergone LT: tyrosinemia (8), methylmalonic acidemia (7), maple syrup urine disease (6), citrullinemia (6), ornithine transcarbamylase deficiency (4), propionic acidemia (2), and argininosuccinate lyase deficiency (2). Average age at transplantation was 3.6 years. Three patients are now deceased. One patient suffered a metabolic stroke posttransplant. No episodes of metabolic decompensation have been noted. Thirty-five patients received LT with generally favorable outcome. None sustained metabolic decompensation posttransplant. As has been reported previously, LT does not ameliorate pre-existing developmental differences or risk to other organ systems. Further research is needed to aid in standardization of care and follow-up, as most patients no longer follow with a geneticist.

Characteristics of continuous venovenous hemodiafiltration in the acute treatment of inherited metabolic disorders.

BACKGROUND: Continuous kidney replacement therapies (CKRT) have been reported to be an effective approach to removing toxic metabolites in inborn errors of metabolism (IEM). The present study evaluates efficiency and complications of CKRT in children with IEM. METHODS: Patients diagnosed with IEM who underwent CKRT in pediatric and neonatal intensive care units were analyzed. CKRT were initiated in patients with persistently high blood ammonia levels (≥ 500 µmol/L), blood ammonia levels > 250 µmol/L in the presence of moderate encephalopathy, high blood leucine levels (≥ 1500 µmol/L), and blood leucine levels < 1500 µmol/L in the presence of deteriorating neurological status or persistent metabolic acidosis. RESULTS: Of 22 patients enrolled, nine (40.9%) Maple syrup urine disease (MSUD), eight (36.4%) urea cycle disorders (UCD), and five (22.7%) organic acidemias (OA). Median age was 72.3 [9.9-1040.8] days. In total, 28 dialysis sessions were analyzed [16 (57.1%) continuous venovenous hemodialysis, and 12 (42.9%) continuous venovenous hemodiafiltration]. A significant decrease was noted in leucine levels (from 1608.4 ± 885.3 to 314.6 ± 109.9 µmol/L) of patients with MSUD, while ammonia levels were significantly decreased in patients with UCD and OA (from 1279.9 ± 612.1 to 85.1 ± 21.6 µmol/L). The most frequent complications of CKRT were thrombocytopenia (60.7%), hypotension (53.6%), and hypocalcemia (42.9%). Median age of patients with hypotension treated with vasoactive medications was significantly lower than median age of those with normal blood pressure. CONCLUSION: CKRT is a reliable approach for effective and rapid removal of toxic metabolites in children with IEM, and CKRT modalities can be safely used and are well-tolerated in infants.

Muscle-directed AAV gene therapy rescues the maple syrup urine disease phenotype in a mouse model.

Maple syrup urine disease (MSUD) is a rare, inherited metabolic disorder characterized by a dysfunctional mitochondrial enzyme complex, branched-chain alpha-keto acid dehydrogenase (BCKDH), which catabolizes branched-chain amino acids (BCAAs). Without functional BCKDH, BCAAs and their neurotoxic alpha-keto intermediates can accumulate in the blood and tissues. MSUD is currently incurable and treatment is limited to dietary restriction or liver transplantation, meaning there is a great need to develop new treatments for MSUD. We evaluated potential gene therapy applications for MSUD in the intermediate MSUD (iMSUD) mouse model, which harbors a mutation in the dihydrolipoamide branched-chain transacylase E2 (DBT) subunit of BCKDH. Systemic delivery of an adeno-associated virus (AAV) vector expressing DBT under control of the liver-specific TBG promoter to the liver did not sufficiently ameliorate all aspects of the disease phenotype. These findings necessitated an alternative therapeutic strategy. Muscle makes a larger contribution to BCAA metabolism than liver in humans, but a muscle-specific approach involving a muscle-specific promoter for DBT expression delivered via intramuscular (IM) administration only partially rescued the MSUD phenotype in mice. Combining the muscle-tropic AAV9 capsid with the ubiquitous CB7 promoter via IM or IV injection, however, substantially increased survival across all assessed doses. Additionally, near-normal serum BCAA levels were achieved and maintained in the mid- and high-dose cohorts throughout the study; this approach also protected these mice from a lethal high-protein diet challenge. Therefore, administration of a gene therapy vector that expresses in both muscle and liver may represent a viable approach to treating patients with MSUD.

Maple syrup urine disease: Characteristics of diagnosis and treatment in 45 patients in Chile.

Maple urine syrup disease (MSUD) is an autosomal recessive disorder characterized by deficient activity of the branched-chain alpha ketoacid dehydrogenase (BCKAD) enzymatic complex due to biallelic variants in the alpha (BCKDHA) or beta (BCKDHB) subunits or the acyltransferase component (DBT). Treatment consists in leucine (LEU), isoleucine (ILE), and valine (VAL) (branched-chain amino acids) dietary restriction and strict metabolic control. to determine the characteristics of the Chilean cohort with MSUD currently in follow-up at Instituto de Nutrición y Tecnología de los Alimentos, during the 1990-2017 period Retrospective analytical study in 45 MSUD cases. Measured: biochemical parameters (LEU, ILE, and VAL), anthropometric evaluation, and neurocognitive development. In 18 cases undergoing genetic study were analyzed according to the gene and protein location, number of affected alleles, and type of posttranslational modification affected. Then, 45 patients with MSUD diagnosis were identified during the period: 37 were alive at the time of the study. Average diagnosis age was 71 ± 231 days. Average serum diagnosis LEU concentrations: 1.463 ± 854.1 µmol/L, VAL 550 ± 598 µmol/L and ILE 454 ± 458 µmol/L. BCKDHB variants explain 89% cases, while BCKDHA and DBT variants explain 5.5% of cases each. Variants p.Thr338Ile in BCKDHA, p.Pro240Thr and p.Ser342Asn in BCKDHB have not been previously reported in literature. Average serum follow-up LEU concentrations were 252.7 ± 16.9 µmol/L in the <5 years group and 299 ± 123.2 µmol/L in ≥5 years. Most cases presented some degree of developmental delay. Early diagnosis and treatment is essential to improve the long-term prognosis. Frequent blood LEU measurements are required to optimize metabolic control and to establish relationships between different aspects analyzed.

Neonatal maple syrup urine disease in China: two novel mutations in the BCKDHB gene and literature review.

OBJECTIVES: To report two novel mutations in the BCKDHB gene with Maple syrup urine disease (MSUD) and compare their data with 52 cases of MSUD reported in the available Chinese literature. METHODS: Clinical data of a case of a newborn with MSUD was retrospectively studied. Literatures on MSUD in the local medical journals from January 1990 till December 2019 in China were reviewed. RESULTS: Two novel BCKDHB mutations c.90_91insCTGGCGCGGGG (p.Phe35TrpfsTer41) and c.80_90del (p.Ala32PhefsTer48) were identified. We found a total of 52 cases of MSUD reports so far. A total of 49 cases had the symptom of poor feeding (94.2%), 50 cases showed poor responses to stimulation (96.2%), 21 cases had odor of maple syrup (40.3%), 29 cases had seizures (55.7%), and 13 cases had respiratory failure (25.0%). The average of the blood ammonia was 127.2 ± 75.0 µmol/L. A total of 18 cases reported the gene testing, among of them 9 cases of BCKDHA mutations, 6 cases of BCKDHB mutations, and 2 cases of DBT mutations. A total of 13 cases (25%) were treated with mechanical ventilation, 50 cases (96.2%) with protein-restricted diet and l-carnitine, 29 cases with thiamine, and only 2 cases were treated with blood purification. Finally, 19 patients (36.5%) were died, 21 cases (40.4%) were improved after treatments. CONCLUSIONS: The clinical phenotype of neonatal MSUD in China belongs to the classical type currently. Suspected patients should have blood or urine branched-chain amino acid levels tested and brain MRI as early as possible to enable early diagnosis, thus improvement in prognosis.

Clinical perspective on the use of human amniotic epithelial cells to treat congenital metabolic diseases with a focus on maple syrup urine disease.

Congenital metabolic diseases are a group of hereditary disorders caused by the deficiency of a single specific enzyme activity. Without appropriate therapy, affected patients suffer severe neurologic disability and eventual death. The current mainstays of management attempt to slow disease progression, but are not curative. Several of these diseases have demonstrated significant benefits from liver transplantation; however, this approach is limited by the morbidity associated with this invasive procedure and a shortage of donor organs. Therefore, there is a need to establish a new strategy for improving the quality of a life for these patients. One potential solution is regenerative therapy using hepatocytes generated from stem cells. Herein, we discuss pertinent issues necessary for clinical application of the human amniotic epithelial cell, a type of placental stem cell. Focusing on maple syrup urine disease as an example, where liver replacement is an effective therapy, we explore this approach from a clinician's perspective.

Liver and/or kidney transplantation in amino and organic acid-related inborn errors of metabolism: An overview on European data.

BACKGROUND: This study provides a general overview on liver and/or kidney transplantation in patients with an amino and organic acid-related disorder (AOA) with the aim to investigate patient characteristics and global outcome in Europe. This study was an initiative of the E-IMD and the AOA subnetwork of MetabERN. METHODS: A questionnaire was sent to all clinically active European Society for the Study of Inborn Errors of Metabolism (SSIEM) members. The questionnaire focused on transplanted individuals with methylmalonic acidemia (MMA), propionic acidemia (PA), maple syrup urine disease (MSUD), and urea-cycle disorders (UCDs). RESULTS: We identified 280 transplanted AOA patients (liver transplantation in 20 MMA, 37 PA, 47 MSUD, and 111 UCD patients, kidney or combined liver and kidney transplantation in 57 MMA patients and undefined transplantation type in 8 MMA patients), followed by 51 metabolic centers. At a median follow-up of 3.5 years, posttransplant survival ranged between 78% and 100%, being the lowest in PA patients. Overall, the risk of mortality was highest within 14 days posttransplantation. Neurological complications were mainly reported in Mut0 type MMA (n = 8). Nonneurological complications occurred in MMA (n = 28), PA (n = 7), and UCD (n = 14) patients, while it was virtually absent in MSUD patients. Only 116/280 patients were psychologically tested. In all, except MSUD patients, the intelligence quotient (IQ) remained unchanged in the majority (76/94, 81%). Forty-one percentage (9/22) of MSUD patient showed improved IQ. CONCLUSION: The survival in AOA individuals receiving liver and/or kidney transplantation seems satisfactory. Evidence-based guidelines, systematic data collection, and improved cooperation between transplantation centers and European Reference Networks are indispensable to improve patient care and outcomes.

Eficacia y seguridad de la fórmula nutricional libre de aminoácidos de cadena ramificada en pacientes con la enfermedad de la orina con olor a jarabe de arce / Efficacy and safety of branched-chain amino acid-free nutritional formula in patients with maple syrup urine disease

INTRODUCCIÓN: El presente dictamen expone la evaluación del producto fórmula nutricional libre de aminoácidos de cadena ramificada comparado con la mejor terapia de soporte nutricional en pacientes con la enfermedad de la orina con olor a jarabe de arce. La enfermedad de la orina con olor a jarabe de arce (EOOJA) es una enfermedad congénita originada por un error innato del metabolismo de aminoácidos. La EOOJA es una enfermedad de carácter autosómico recesivo debida a mutaciones en los genes de la deshidrogenasa cetoácida de cadena ramificada (BCKAD, por sus siglas en inglés) que conduce a la acumulación de leucina, isoleucina, valina y aloisoleucina y los correspondientes cetoácidos de cadena ramificada (BCKA, por sus siglas en inglés) en los tejidos y el plasma. Los niveles elevados de estas sustancias originan problemas del crecimiento y desarrollo, cuadros agudos de encefalopatía e incluso pueden ser fatales. La enfermedad de la orina con olor a jarabe de arce (EOOJA) es una enfermedad congénita originada por un error innato del metabolismo de aminoácidos. La EOOJA es una enfermedad de carácter autosómico recesivo debida a mutaciones en los genes de la deshidrogenasa cetoácida de cadena ramificada (BCKAD, por sus siglas en inglés) que conduce a la acumulación de leucina, isoleucina, valina y aloisoleucina y los correspondientes cetoácidos de cadena ramificada (BCKA, por sus siglas en inglés) en los tejidos y el plasma. Los niveles elevados de estas sustancias originan problemas del crecimiento y desarrollo, cuadros agudos de encefalopatía e incluso pueden ser fatales. METODOLOGÍA: Se realizó una búsqueda sistemática de la literatura con el objetivo de identificar evidencia sobre el uso de la fórmula nutricional libre de BCAA en pacientes con EOOJA (conocida en inglés como Maple syrup urine disease). Para identificar documentos de interés para el presente dictamen, se buscó evidencia disponible en las siguientes bases de datos bibliográficas: PubMed, The Cochrane Library y LILACS. Adicionalmente, se realizó una búsqueda en sitios web pertenecientes a grupos que realizan evaluaciones de tecnologías sanitarias y guías de práctica clínica, incluyendo The Canadian Agency for Drugs and Technologies in Health (CADTH), Scottish Medicines Consortium (SMC), The National Institute for Health and Care Excellence (NICE), Institute for Quality and Efficiency in Health Care (IQWiG), el portal BRISA (Base Regional de Informes de Evaluación de Tecnologías en Salud de las Américas) y sitios web de organizaciones internacionales en nutrición clínica, enfermedades raras o congénitas, medicina, pediatría o de enfermedades metabólicas. Por último, se llevó a cabo una búsqueda manual en el portal ClinicalTrials.gov del National Institutes of Health. RESULTADOS: Se describe la evidencia disponible según el tipo de publicación, siguiendo lo indicado en los criterios de elegibilidad. CONCLUSIONES: El presente documento evaluó la mejor evidencia científica disponible hasta la actualidad (marzo del 2020) sobre el uso de fórmula nutricional libre BCAA en pacientes con EOOJA. La GPC elaborada por SERC y GMDI recomienda el uso de fórmulas nutricionales libres de BCAA en pacientes con EOOJA o sospecha de EOOJA, con EOOJA en fase de mantenimiento o en la fase aguda de la enfermedad. Para la fase aguda, recomienda el empleo de una fórmula nutricional con proteína libre de BCAA por vía enteral como complemento a la nutrición parenteral hasta que el paciente puedo recibir su requerimiento nutricional total por vía enteral. La GPC de SERC y GMDI considera que la evidencia disponible para el uso de esta fórmula es razonable.  Los reportes de pacientes con EOOJA señalan al empleo de la fórmula libre de BCAA como parte del manejo nutricional en pacientes con esta condición clínica. El uso de esta fórmula nutricional en los pacientes con EOOJA de estos reportes de caso se condice con la recomendación de la GPC y lo descrito en recursos de soporte a la toma de decisión clínica como UpToDate y DynaMed. La evidencia respecto al uso de la fórmula nutricional libre de BCAA en pacientes con la EOOJA es escasa. No obstante, existe plausibilidad biológica para pensar en que esta fórmula sería útil para el manejo nutricional de pacientes con EOOJA, dado que estas aportan los requerimientos nutricionales energéticos mediante una administración controlada de BCAA.  Los expertos clínicos de EsSalud señalan que en la institución no existe actualmente la disponibilidad de un producto nutricional para pacientes con EOOJA. Por otro lado, señalan tener experiencia en el empleo de fórmulas nutricionales libres de BCAA, observando beneficio en indicadores de peso, talla, desarrollo cognitivo y buena tolerancia al producto. Lo señalado por los expertos clínicos esta en línea con lo descrito en las GPC y en recursos de soporte a la toma de decisión clínica como UpToDate y DynaMed. Por lo expuesto, el Instituto de Evaluaciones de Tecnologías en Salud e Investigación ­ IETSI- aprueba el de la fórmula nutricional libre de BCAA en pacientes con EOOJA, según lo establecido en el Anexo N° 01. La vigencia del presente dictamen preliminar es de un año a partir de la fecha de publicación. Así, la continuación de dicha aprobación estará sujeta a la evaluación de los resultados obtenidos y de nueva evidencia que pueda surgir en el tiempo.

Genotype-phenotype correlation of 33 patients with maple syrup urine disease.

Maple syrup urine disease (MSUD) is a rare autosomal recessive inherited disorder due to defects in the branched-chain α-ketoacid dehydrogenase complex (BCKDC). MSUD varies in severity and its clinical spectrum is quite broad, ranging from mild to severe phenotypes. Thirty-three MSUD patients were recruited into this study for molecular genetic variant profiling and genotype-phenotype correlation. Except for one patient, all other patients presented with the classic neonatal form of the disease. Seventeen different variants were detected where nine were novel. The detected variants spanned across the entire BCKDHA, BCKDHB and DBT genes. All variants were in homozygous forms. The commonest alterations were nonsense and frameshift variants, followed by missense variants. For the prediction of variant's pathogenicity, we used molecular modeling and several in silico tools including SIFT, Polyphen2, Condel, and Provean. In addition, six other tools were used for the prediction of the conservation of the variants' sites including Eigen-PC, GERP++, SiPhy, PhastCons vertebrates and primates, and PhyloP100 rank scores. Herein, we presented a comprehensive characterization of a large cohort of patients with MSUD. The clinical severity of the variants' phenotypes was well correlated with the genotypes. The study underscores the importance of the use of in silico analysis of MSUD genotypes for the prediction of the clinical outcomes in patients with MSUD.

Diálisis peritoneal en un neonato con enfermedad de la orina con olor a jarabe de arce. A propósito de un caso / Peritoneal dialysis in a neonate with maple syrup urine disease. A case report

La enfermedad de jarabe de arce es una entidad autosómica recesiva producida por un error congénito en el metabolismo de tres aminoácidos esenciales de cadena ramificada: valina, leucina e isoleucina. La forma neonatal de esta enfermedad se manifiesta por un cuadro de compromiso neurológico grave y progresivo, asociado a un olor peculiar de la orina, consecuencia de la eliminación del exceso de estos aminoácidos. Este olor a azúcar quemada remeda a la melaza obtenida de los arces, lo que da nombre a esta enfermedad. El mejor método para eliminar estos tóxicos es la hemodiafiltración, pero, en los centros en los que esta práctica no es posible, la diálisis peritoneal constituye una alternativa.Se presenta a un recién nacido con leucinosis, con compromiso grave del sistema nervioso central, en quien la diálisis peritoneal fue de utilidad para superar la descompensación metabólica.

Maple syrup disease is an autosomal recessive entity caused by a congenital error in the metabolism of three essential branched-chain amino acids: valine, leucine and isoleucine. The neonatal form of this disease is expressed by a severe and progressive neurological compromise, associated with a peculiar smell of urine, a consequence of the elimination of the excess of these amino acids. This smell of burnt sugar mimics the molasses obtained from maples, which gives its name to this disease. The best method to eliminate these toxins is hemodiafiltration, but in centers where this practice is not possible, peritoneal dialysis is an alternative.We present a newborn with leukinosis with severe central nervous system involvement in whom peritoneal dialysis was useful to overcome metabolic decompensation.

[Peritoneal dialysis in a neonate with maple syrup urine disease. A case report]. / Diálisis peritoneal en un neonato con enfermedad de la orina con olor a jarabe de arce. A propósito de un caso.

Maple syrup disease is an autosomal recessive entity caused by a congenital error in the metabolism of three essential branchedchain amino acids: valine, leucine and isoleucine. The neonatal form of this disease is expressed by a severe and progressive neurological compromise, associated with a peculiar smell of urine, a consequence of the elimination of the excess of these amino acids. This smell of burnt sugar mimics the molasses obtained from maples, which gives its name to this disease. The best method to eliminate these toxins is hemodiafiltration, but in centers where this practice is not possible, peritoneal dialysis is an alternative. We present a newborn with leukinosis with severe central nervous system involvement in whom peritoneal dialysis was useful to overcome metabolic decompensation.

La enfermedad de jarabe de arce es una entidad autosómica recesiva producida por un error congénito en el metabolismo de tres aminoácidos esenciales de cadena ramificada: valina, leucina e isoleucina. La forma neonatal de esta enfermedad se manifiesta por un cuadro de compromiso neurológico grave y progresivo, asociado a un olor peculiar de la orina, consecuencia de la eliminación del exceso de estos aminoácidos. Este olor a azúcar quemada remeda a la melaza obtenida de los arces, lo que da nombre a esta enfermedad. El mejor método para eliminar estos tóxicos es la hemodiafiltración, pero, en los centros en los que esta práctica no es posible, la diálisis peritoneal constituye una alternativa. Se presenta a un recién nacido con leucinosis, con compromiso grave del sistema nervioso central, en quien la diálisis peritoneal fue de utilidad para superar la descompensación metabólica.

Branched-chain α-ketoacid dehydrogenase deficiency (maple syrup urine disease): Treatment, biomarkers, and outcomes.

Over the past three decades, we studied 184 individuals with 174 different molecular variants of branched-chain α-ketoacid dehydrogenase activity, and here delineate essential clinical and biochemical aspects of the maple syrup urine disease (MSUD) phenotype. We collected data about treatment, survival, hospitalization, metabolic control, and liver transplantation from patients with classic (i.e., severe; n = 176), intermediate (n = 6) and intermittent (n = 2) forms of MSUD. A total of 13,589 amino acid profiles were used to analyze leucine tolerance, amino acid homeostasis, estimated cerebral amino acid uptake, quantitative responses to anabolic therapy, and metabolic control after liver transplantation. Standard instruments were used to measure neuropsychiatric outcomes. Despite advances in clinical care, classic MSUD remains a morbid and potentially fatal disorder. Stringent dietary therapy maintains metabolic variables within acceptable limits but is challenging to implement, fails to restore appropriate concentration relationships among circulating amino acids, and does not fully prevent cognitive and psychiatric disabilities. Liver transplantation eliminates the need for a prescription diet and safeguards patients from life-threatening metabolic crises, but is associated with predictable morbidities and does not reverse pre-existing neurological sequelae. There is a critical unmet need for safe and effective disease-modifying therapies for MSUD which can be implemented early in life. The biochemistry and physiology of MSUD and its response to liver transplantation afford key insights into the design of new therapies based on gene replacement or editing.

The utility of dried blood spot monitoring of branched-chain amino acids for maple syrup urine disease: A retrospective chart review study.

BACKGROUND: Branched-chain amino acid (BCAA) concentrations must be tracked and maintained within an optimal range to minimize disease phenotypes in patients with maple syrup urine disease (MSUD). In 2014, the Hospital for Sick Children (SickKids) implemented a dried blood spot (DBS) home monitoring system, allowing patients to track BCAA concentrations without the inconvenience of having to travel to the hospital. METHODS: We conducted a retrospective chart review study (n = 15) to assess the impacts of DBS monitoring implementation on biochemical control. Furthermore, we explored relationships among various MSUD patient parameters, including monitoring frequency, age, biochemical control, and hospitalizations. RESULTS: There was a 35% increase in the proportion of LEU concentrations that met recommended targets post-DBS monitoring implementation. Monitoring frequency was positively associated with better biochemical control in the newborn period (r = 0.68, p = 0.046). Frequency of hospital visits decreased steadily throughout life. CONCLUSION: DBS monitoring has resulted in a sharp increase in monitoring frequency, which is further correlated with biochemical control. Younger patients are more likely to visit the hospital and respond better to increased monitoring efforts. We recommend that DBS monitoring be adopted by other centers more broadly to improve metabolic control in MSUD patients.

Treatment of maple syrup urine disease with high flow hemodialysis in a neonate.

Aygün F, Kiykim E, Aktuglu-Zeybek Ç, Zubarioglu T, Cam H. Treatment of maple syrup urine disease with high flow hemodialysis in a neonate. Turk J Pediatr 2019; 61: 107-110. Continious renal replacement therapy (CRRT) is a well recognizied treatment of choice in acute renal failure, however CRRT became a preferred treatment of metabolic emergencies with high leucine and ammonia levels like Maple syrup urine disease (MSUD). MSUD is a rare metabolic disorder caused by deficiency in the activity of the branched-chain a-ketoacid dehydrogenase complex. The toxic accumulation of branched chain amino acids during acute metabolic decompensation is associated with the appearance of permanent neurological symptoms. Four patients were admitted to our pediatric intensive care department with complains of poor feeding, vomitting, irratibility and coma. Physical examination of the neonates were similar having stupor, hypotonia and depressed newborn reflexes. The leucine levels were between 930-4400 µmol/L. The diagnosis of MSUD was confirmed in all four. They were treated successfully with high flow CRRT having the rates were between 4120 ml/h/1.73m2 and 9830 ml/h/1.73m2. Early treatment is essential to prevent neurotoxicity and death. CRRT is a choice of treatment in metabolic crisis of MSUD. Herein, we report the successful treatment of acute metabolic decompensation of MSUD with CRRT in 4 neonates.

[Progress of research on Maple syrup disease].

Maple syrup disease (MSUD) is a rare autosomal recessive disorder caused primarily by mutations of branched-chain keto acid dehydrogenase complex (BCKDC). BCKDC includes at least four pathogenic genes of BCKDHA, BCKDHB, DLD and DBT. The clinical manifestations of MSUD are complex, and the main symptoms at the early stage include difficulty in feeding, drowsiness, change in muscle tone and special urine flavor of maple syrup. As the disease progresses, convulsion, hypoglycemia, coma and systemic failure may occur. MSUD is easily missed or misdiagnosed during the neonatal period. This paper provides a review for recent progress made in research on MSUD including etiology, physiopathology, clinical manifestation, auxiliary examination and treatment, with a particular emphasis on genetic testing and treatment.