Manejo inicial de la hiperamonemia aguda en pediatría / Initial management of acute hyperammonemia in pediatrics

La hiperamonemia constituye una emergencia médica. No existen publicaciones que hagan referencia a la disponibilidad de recursos, insumos y conocimientos necesarios para el manejo inicial de esta por parte del pediatra en nuestro país, pero, según la experiencia de los autores, los recursos necesarios no se encuentran disponibles los 365 días del año en una gran porción de nuestro territorio. Sobre la base de este estado de situación, de una revisión bibliográfica internacional sobre el tema y de la experiencia de los autores, se elaboraron una serie de recomendaciones para el manejo pediátrico inicial de esta emergencia, que tienen como objetivo poder reducir las deficiencias, permitir una sospecha clínica adecuada que lleve a un diagnóstico y tratamiento de emergencia oportunos, con utilización racional de recursos farmacológicos (algunos de ellos de alto costo), para reducir la morbimortalidad que asocia la patología.

Hyperammonemia is a medical emergency. There are no publications regarding the availability of resources, supplies, and knowledge necessary for the initial management of hyperammonemia by pediatricians in Argentina; however, according to the authors' experience, the necessary resources are not available all year round in a large portion of our territory. Based on such state of affairs, an international bibliographic review on this topic and the authors' experience, we developed a series of recommendations for the initial pediatric management of this emergency, with the objective of reducing deficiencies, allowing adequate clinical suspicion leading to a timely diagnosis and emergency management and a rational use of pharmacological resources (some of which are costly) to reduce the morbidity and mortality associated with hyperammonemia.

Glyceryl phenylbutyrate in the treatment of argininosuccinate synthetase deficiency: a case report / 中华实用儿科临床杂志

Clinical data of a child with high blood ammonia and suspected argininosuccinate synthetase deficiency (ASSD) in Hunan Children′s Hospital were retrospectively analyzed, including data of mass spectra for blood amino acids and acyl carnitine, urine organic acid analysis and whole exome sequencing.After the exact diagnosis of ASSD and being approved by the Administrative Regulation for Import Medical Devices Urgently Needed in Boao Lecheng International Medical Tourism Pilot Zone of Hainan Free Trade Port, the patient was medicated with Glyceryl phenylbutyrate (GPB) and followed up.The patient was a boy aged 7 years and 8 months, who presented at the Neurology Department of Hunan Children′s Hospital for sleepiness, abnormal mental behavior and personality change for 1 week on December 2, 2021.Before GPB treatment, the highest blood ammonia, alanine aminotransferase and aspartate transaminase were 325.2 μmol/L, 465.7 IU/L and 277.3 IU/L, respectively.Genetic metabolism assay of blood and urine showed a significantly increased citrulline at 697.42 μmol/L; urine organic acid analysis showed increased urinary orotic acid at 144.2 μmol/L, and increased uracil at 65.1 μmol/L.A pure heterozygous variant of the ASS1 gene (c.1087C>T, p.R363W) was detected.After GPB treatment, the blood ammonia levels were 21.3 μmol/L, 54.6 μmol/L and 62.4 μmol/L on the 41 st, 90 th and 146 th days, respectively.Until July 20, 2022 follow-up visit, the patient recovered well without adverse events.This was the first ASSD child in China who was treated with GPB.This case report provided therapeutic experience of ASSD in our country.ASSD has a high mortality rate and unexplained abnormal mental behavior.It is necessary to timely measure blood ammonia, and a series of urea cycle disorders should be well concerned.The diagnosis and management of ASSD rely on the data of metabolism examination and genetic testing.

Newborn screening for ornithine transcarbamylase deficiency in Zhejiang Province and the follow-up analysis / 中华实用儿科临床杂志

Objective:To investigate the incidence, clinical characteristics and prognosis of ornithine transcarbamylase deficiency(OCTD) in newborns in Zhejiang Province.Methods:A retrospective research was conducted.A total of 4 261 036 newborns from Department of Genetics and Metabolism, Children′s Hospital, Zhejiang University School of Medicine, between January 2009 and December 2021 were screened for inherited metabolic disorders using tandem mass spectrometry.OCTD was confirmed by urine organic acid and OTC gene analysis.Patients with OTCD received guidance on diet and lifestyle management, and were treated with citrulline and arginine.Long-term follow-up was performed.Their growth and intellectual development were evaluated. Results:A total of 7 patients with OCTD were diagnosed, with an incidence of 1.6/1 million.All patients were males.Two patients had neonatal-onset OCTD, and the other 5 had late-onset OCTD.Symptoms occurred several times in 6 patients, inducing hyperammonemia and hepatic impairment.One patient had no clinical manifestation.One patient died in the neonatal period.Blood citrulline levels were decreased in 7 patients to varying degrees.Uracil levels were increased in 4 patients, and 1 of them was complicated with elevated orotic acid levels.All patients had hemizygote variations in the OTC gene, including 6 missense variations(c.604C>T, c.386G>A, c.779T>C, c.1019C>T, c.594C>G, c.931G>A) and 1 intron variation(c.514-35C>G). Two variants(c.594C>G, c.514-35C>G) were never reported previously. Conclusions:The OTCD incidence by newborn screening is low with 1.6/1 million in Zhejiang province.All patients are males and present hypocitrullinemia.The clinical manifestations of OTCD are highly heterogeneous.The neonatal-onset form is severe and survivors always suffer serious sequelae.The late-onset form is mostly manifested with hyperammonemia and hepatic impairment.There may be association between phenotype and genotype.Two novel OTC variants are identified, which further expands the mutational spectrum.

Actualización sobre la lactancia materna en los recién nacidos con errores innatos del metabolismo intermediario / Update on breastfeeding in newborns with inborn errors of intermediary metabolism

Resumen Los errores innatos del metabolismo intermediario (EIMi) son un grupo de enfermedades monogénicas que afectan alguna vía del metabolismo de las proteínas, los hidratos de carbono o los lípidos; cuando no son tratados a tiempo, se asocian con una elevada morbimortalidad. A la fecha, la piedra angular del tratamiento de los EIMi ha sido la terapia nutricional, cuyo propósito es evitar la acumulación de metabolitos tóxicos al restringir los sustratos que están involucrados en la vía afectada. El manejo nutricional en lactantes incluye una fórmula metabólica sin los nutrimentos involucrados en el EIMi más el aporte de alimentación al seno materno o fórmula infantil. Por el perfil de aminoácidos, la proporción de ácidos grasos esenciales y la protección contra enfermedades, la leche materna resulta un alimento ideal para los pacientes con EIMi. El objetivo de esta revisión de la literatura sobre la lactancia materna en algunos EIMi es servir de guía para el personal de salud involucrado en la atención médica de estos pacientes. La lactancia materna puede ser llevada a cabo de forma exitosa en pacientes con EIMi siempre que exista un seguimiento estrecho y continuo, de preferencia en centros especializados. El profesional de la nutrición y el pediatra deben individualizar las recomendaciones para proporcionar una lactancia a libre demanda en conjunto con una fórmula metabólica o una lactancia materna cuantificada, y con ello lograr una adecuada evolución en estos pacientes.

Abstract Inborn errors of intermediary metabolism (IEiM) are a group of monogenic disorders that affect a metabolic pathway of proteins, carbohidrates, or lipids; when not treated timely, IEiM are associated with high morbidity and mortality. To date, nutritional therapy is the cornerstone of treatment for patients with IEiM, which aims to prevent the accumulation of toxic metabolites by restricting the substrates involved in the affected pathway. Nutritional management in infants includes a metabolic formula free of the nutrients involved in IEiM and breastmilk or infant formula. Because of its amino acid profile, the content of essential fatty acids, and protection against disease, breast milk is an excellent food for patients with IEiM. This literature review on breastfeeding in some IEiM aims to serve as a guide for health care personnel involved in the medical care of these patients. Breastfeeding can be successfully carried out in patients with IEiM as long as there is a close and continuous follow-up, preferably in specialized centers. The nutrition professional and the pediatrician should individualize the recommendations to provide on-demand breastfeeding in conjunction with metabolic formula or quantified breastfeeding to achieve a good clinical evolution in this group of patients.

Aciduria argininosuccínica: informe de un caso de inicio neonatal / Argininosuccinic aciduria: Neonatal case report

Los defectos del ciclo de la urea son enfermedades metabólicas hereditarias que se producen por defecto en una de las enzimas encargadas de la desintoxicación del amonio, lo que genera su acumulación en el organismo. Las manifestaciones clínicas pueden presentarse en la etapa neonatal, con morbimortalidad elevada, o de forma tardía. La heterogeneidad de los síntomas y la falta de sospecha clínica en neonatos conducen a un diagnóstico erróneo y se puede confundir con sepsis neonatal o hemorragias cerebrales. El aumento de amonio plasmático en el examen bioquímico orienta su diagnóstico hacia un defecto del ciclo de la urea.La aciduria argininosuccínica es el tercer defecto más frecuente del ciclo de la urea y es causada por deficiencia de la enzima argininosuccínico liasa. Se presenta el informe de un caso de inicio neonatal. Los objetivos son enfatizar en su sospecha diagnóstica y proponer herramientas diagnósticas tempranas, como su incorporación a la pesquisa metabólica neonatal.

Urea cycle defects are inborn errors of metabolism produced by a defect in one of the enzymes responsible for the detoxification of ammonia, which generates its accumulation in the body. The clinical manifestations can present early, with high morbidity and mortality, or late onset. The heterogeneity of the symptoms and the lack of clinical suspicion in neonates leads to a wrong diagnosis, which can be confused with neonatal sepsis or cerebral hemorrhages. The increase in plasma ammonia in the biochemical examination orients his diagnosis towards a defect of the urea cycle.Argininosuccinic aciduria is the third most frequent defect of the urea cycle, and is caused by a argininosuccinate lyase deficiency. A neonatal onset case report is presented. The objective is to emphasize its diagnostic suspicion, and to propose early diagnostic tools such as its incorporation into the neonatal metabolic screening.

Un trastorno poco frecuente del ciclo de la urea en un recién nacido: deficiencia de N-acetilglutamato sintasa / A rare urea cycle disorder in a neonate: N-acetylglutamate synthetase deficiency

Los trastornos del ciclo de la urea (TCU) son enfermedades hereditarias con un posible desenlace desfavorable por hiperamoniemia grave. Se informa de una bebé con deficiencia de N-acetilglutamato sintasa (NAGS), quien tenía succión débil e hipotonicidad. Al examinarla, se observó hepatomegalia. El hemograma, los análisis y la gasometría eran normales, y las proteínas de la fase aguda, negativas. En los análisis, no se observaron cetonas en sangre, pero sí concentraciones elevadas de amoníaco. Las pruebas metabólicas no fueron concluyentes. Se inició el tratamiento de emergencia inmediatamente y recibió el alta el día 15 después del ingreso. Se confirmó deficiencia de NAGS mediante análisis de ADN. La paciente no tiene restricciones alimentarias ni toma medicamentos, excepto N-carbamil glutamato (NCG). La deficiencia de NAGS es el único TCU que puede tratarse específica y eficazmente con NCG. La detección temprana permite iniciar un tratamiento temprano y evitar los efectos devastadores de la hiperamoniemia

Urea cycle disorders (UCD), are genetically inherited diseases that may have a poor outcome due to to profound hyperammonemia. We report the case of a baby girl diagnosed as N-acetylglutamate synthase (NAGS) deficiency.The patient was evaluated due to diminished sucking and hypotonicity. Physical examination showed hepatomegaly. Complete blood count, biochemical values and blood gas analyses were normal, acute phase reactants were negative. Further laboratory analyses showed no ketones in blood and highly elevated ammonia. Metabolic tests were inconclusive. Emergency treatment was initiated immediately and she was discharged on the 15th day of admission. NAGS deficiency was confirmed by DNA-analysis. She is now without any dietary restriction or other medication, except N-carbamylglutamate (NCG).NAGS deficiency is the only UCD which can be specifically and effectively treated by NCG. Early recognition of disease will lead to early treatment that may prohibit devastating effects of hyperammonemia

Clinical research of two cases of late-onset ornithine carbamoyltransferase deficiency / 中华神经科杂志

Objective To explore the clinical characteristics of late-onset ornithine carbamoyltransferase deficiency (OTCD) in order to improve the clinicians' understanding of this disease.Methods The clinical,therapeutic and follow-up data of two patients with late-onset OTCD diagnosed in the Department of Neurology,Qilu Hospital of Shandong University from November 2017 to February 2018 were collected and analyzed.Results Case 1 is a 17-year-old male who was admitted into Qilu Hospital with recurrent dizziness and vomiting for 4 months,sudden mental abnormality and convulsion for 3 days.The liver dysfunction,respiratory alkalosis and hyperammonemia (434 μmol/L) had been found before his admission.His blood ammonia fluctuated obviously from 180 μ mol/L to 2998 μmol/L,though he was given hemodialysis and arginine infusion,and died on the fourth day after admission.Case 2 is a 15-year-old male,complained with recurrent dizziness,vomiting,bluntness and somnolence for 20 days.He was found with hyperammonemia (600 μmol/L) and liver dsyfunction in a local hospital.He was getting better after intravenous administration of arginine and liver protective drugs.After admission,the blood ammonia,liver function and amino acids,acylcarnitine profiling in dried blood spots,and organic acid analysis in urine were normal,and he has not recurred since restriction of protein diet.Brain magnetic resonane imaging of both patients showed cytotoxic edema of bilateral frontal lobe and insular cortex,and their genetic detection both showed c.119G＞A(p.R40H) hemizygous pathogenic mutation of OTC gene inherited from their respective mothers.Conclusion Unexplained hyperammonemia and acute encephalopathy with insular and frontal cortical involvement should be on the alert to the urea cycle disorders,especially OTCD.Early diagnosis and reasonable treatment are the key to changing the prognosis.

Mutation Spectrum and Genotype-Phenotype Correlation in a Cohort of Argentine Patients with Ornithine Transcarbamylase Deficiency: A Single-Center Experience

Abstract X-linked ornithine transcarbamylase deficiency (OTCD) is the most common urea cycle disorder. Hemizygous males with complete deficiency manifest neonatal acute hyperammonemia, while those with partial deficiency have a late presentation. The symptomatology of heterozygotes depends on the inactivation pattern of X chromosome. Hyperammonemic episodes can cause neurological damage and are potentially fatal. Here, we match clinical, biochemical, and molecular findings with bioinformatics analyses to report genotype-phenotype correlations in 14 Argentine patients with OTCD from 11 unrelated families: 4 hemizygotes with neonatal onset (complete OTC gene deletion, 533C > T, c.540+1G > A, c.697delG); 4 hemizygotes with late onset (c.216+1G > A, c.386G > A, c.622G > A, c.829C > T); and 6 symptomatic heterozygotes (complete OTC gene deletion, c.533C > T, c.452T > G, c.540+1G > A, dupE1-9/delE10). Three of these mutations were previously unreported: c.540+1G > A, c.697delG, and dup1-9/del10. Our data highlight the relevance of combining molecular and bioinformatics analyses for accurate diagnosis and outcome prediction in suspected patients with OTCD and the importance of carrier testing for effective genetic counseling.

Citrulinemia tipo I con insuficiencia hepática recurrente en un niño / Citrullinemia type I with recurrent liver failure in a child

La citrulinemia tipo I es un desorden autosómico recesivo causado por la mutación del gen ASS1, que expresa argininosuccinato sintetasa, enzima limitante del ciclo de la urea. Las variantes clásicas están asociadas con la forma neonatal/infantil, que llevan a hiperamoniemia y a la muerte si el tratamiento no es instaurado. Los síntomas iniciales de los trastornos del ciclo de la urea incluyen deterioro neurológico con leve o moderado daño hepático. Reportamos un caso de falla hepática recurrente en un lactante con diagnóstico de citrulinemia tipo I sin compromiso neurológico grave, que fue derivado a nuestro centro para trasplante hepático. La falla hepática aguda puede ser causada por una gran variedad de desórdenes, dentro de los que se incluyen errores congénitos del metabolismo. El tratamiento adecuado de los trastornos del ciclo de la urea y, en particular, la citrulinemia I puede evitar la necesidad de un trasplante.

Citrullinemia type I is an autosomal recessive disorder caused by mutation of the gene expressing ASS1 argininosuccinate synthetase, limiting enzyme of the urea cycle. The classic variants are associated with neonatal/infantile forms that cause hyperammonemia leading to death if treatment is not established. Initial symptoms of disorders of the urea cycle include neurological impairment with mild or moderate liver damage. We report a case of recurrent liver failure in an infant diagnosed with type I citrullinemia without severe neurological involvement that was referred to our center for liver transplantation. Acute liver failure can be caused by a wide range of disorders in which inborn errors ofmetabolism are included. Appropriate treatment of disorders of the urea cycle and in particular citrullinemia I can avoid the need for a transplant.

Novel Pathogenic Variant (c.580C>T) in the CPS1 Gene in a Newborn With Carbamoyl Phosphate Synthetase 1 Deficiency Identified by Whole Exome Sequencing

Diagnosis of the urea cycle disorder (USD) carbamoyl-phosphate synthetase 1 (CPS1) deficiency (CPS1D) based on only the measurements of biochemical intermediary metabolites is not sufficient to properly exclude other UCDs with similar symptoms. We report the first Korean CPS1D patient using whole exome sequencing (WES). A four-day-old female neonate presented with respiratory failure due to severe metabolic encephalopathy with hyperammonemia (1,690 µmol/L; reference range, 11.2-48.2 µmol/L). Plasma amino acid analysis revealed markedly elevated levels of alanine (2,923 µmol/L; reference range, 131-710 µmol/L) and glutamine (5,777 µmol/L; reference range, 376-709 µmol/L), whereas that of citrulline was decreased (2 µmol/L; reference range, 10-45 µmol/L). WES revealed compound heterozygous pathogenic variants in the CPS1 gene: one novel nonsense pathogenic variant of c.580C>T (p.Gln194*) and one known pathogenic frameshift pathogenic variant of c.1547delG (p.Gly516Alafs*5), which was previously reported in Japanese patients with CPS1D. We successfully applied WES to molecularly diagnose the first Korean patient with CPS1D in a clinical setting. This result supports the clinical applicability of WES for cost-effective molecular diagnosis of UCDs.

A Novel SLC25A15 Mmutation Causing Hyperornithinemia-Hyperammonemia-Homocitrullinuria Syndrome

Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome (HHH syndrome) is a neurometabolic disorder with highly variable clinical severity ranging from mild learning disability to severe encephalopathy. Diagnosis of HHH syndrome can easily be delayed or misdiagnosed due to insidious symptoms and incomplete biochemical findings, in that case, genetic testing should be considered to confirm the diagnosis. HHH syndrome is caused by biallelic mutations of SLC25A15, which is involved in the urea cycle and the ornithine transport into mitochondria. Here we report a boy with spastic paraplegia and asymptomatic younger sister who have compound heterozygous mutations of c.535C>T (p.R179*) and c.116C>A (p.T39K) in the SLC25A15 gene. We identified that p.T39K mutation is a novel pathogenic mutation causing HHH syndrome and that p.R179*, which is prevalent in Japanese and Middle Eastern heritage, is also found in the Korean population.

Déficit de ornitina transcarbamilasa: Caso clínico / Ornithine carbamoyltransferase deficiency: A clinical case

Los trastornos del ciclo de la urea suponen hasta el 60% de las hiperamoniernias graves neonatales. La base de los trastornos de este ciclo deriva en el déficit de una de sus enzimas. El déficit de la enzima ornitina transcarbamilasa es el más frecuente. Su pronóstico dependerá del grado de deficiencia enzimàtica, la edad, la precocidad del diagnóstico e inicio del tratamiento. Presentamos el caso de un adolescente que, a partir de un cuadro de parálisis facial periférica tratado con prednisona, presentó agravamiento de su estado general y falleció a los pocos días. Las cifras elevadas de amoniaco en sangre hicieron sospechar tardíamente de una alteración congénita del ciclo de la urea, que fue confirmada por su estudio genético post mortem. Se estudiaron los familiares y se asesoró a los afectos y portadores. Reflexionamos sobre la importancia de los programas de cribado neonatal y la posibilidad de aplicarlos en la detección de los errores congénitos del metabolismo.

Disorders of urea cycle account for up to 60% of severe neonatal hyperamoniemias. The base of this cycle disorders results in a deficit of its enzymes. Deficiency of the enzyme ornithine transcarbamylase is the most frequently detected. The prognosis depends on the degree of enzyme deficiency, age, early diagnosis and initiation of treatment. We report the case of a teenager who was treated with prednisone because of a peripheral facial palsy. He showed a progressive worsening and died a few days later. The high levels of ammonia made suspect a congenital disorder of urea cycle. The postmortem genetic study confirmed it. We studied the family and advised carriers. We reflect about the importance of the neonatal screening programs and their applicability for detection of inborn errors of metabolism.

Multidisciplinary perinatal management of a woman and her baby with ornithine transcarbamylase deficiency / 中华围产医学杂志

Objective To investigate the clinical features and gene mutation of a newborn with neonatal-onset ornithine transcarbamylase deficiency (OTCD) and report the multidisciplinary perinatal management of the mother with late-onset OTCD.Methods The clinical features,biochemical data and the treatment of a newborn boy with OTCD and his mother admitted by Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine in April,2013,were collected.The ornithine transcarbamylase (OTC) gene in the family was analyzed.Results Serum ammonium in the male newborn gradually increased to 1 020 μ mol/L at 48 h after birth.His blood amino acids level and urine organic acid level showed a pattern indicative of OTCD [blood arginine (97.43 μ mol/L,reference 1.00-25.00 μ mol/L),citrulline (27.43 μ mol/L,reference 4.00-30.00 μ mol/L),ornithine (161.66 μ mol/L,reference 10.00-120.00 μ mol/L) and methionine (70.45 μ mol/L,reference 10.00-50.00 μ mol/L); urine uracil (67.11 μ mol/mol Crea,reference 0.00-7.00 μ mol/mol Crea) and orotic acid (1 372.66 μ mol/mol Crea,reference 0.00-1.50 μ mol/mol Crea)].DNA studies revealed a c.583G ＞ A (G195R) homozygous mutation of the OTC gene.His mother was heterozygous for OTCD and developed acute hyperammonemia during pregnancy.Her blood showed a normal-leveled arginine (8.44 μ mol/L,reference 1.50-25.00 μ mol/L),a normal-leveled citrulline(8.41 μ mol/L,reference 7.00-35.00 μ mol/L),an elevated glutamate(279.15 μ mol/L,reference 45.00-200.00 μ mol/L).Her urine uracil (51.55 μ mol/mol Crea,reference 0.00-7.00 μ mol/mol Crea) and orotic acid (38.75 μ mol/mol Crea,reference 0.00-1.50 μ mol/mol) were elevated.Successful management of her prenatal and postpartum blood ammonia level was achieved after administration of pharmacologic nitrogen scavengers and protein limitation.DNA studies revealed a c.583G ＞ A (G195R) heterozygous mutation in the newborn's mother and grandmother.Conclusions General management on pregnant OTCD women is effective.Male newborn patients often have a poor prognosis.

Molecular diagnosis of urea cycle disorders: Current global scenario.

Urea cycle disorders are a group of inborn error of metabolism, characterized by hyperammonemia, metabolic alkalosis and clinical features of encephalopathy. These are among the commonest types of inborn errors of metabolism with a frequency of 1 in 8,000 to 1 in 30,000 in different population. This encompasses 5 major disorders, corresponding with deficiency of each step in the urea cycle, namely ornithine transcarbamoylase (OTC) deficiency, argininosuccinate lyase (ASL) deficiency, carbamoyl phosphate synthetase (CPS) deficiency, citrullinemia and argininemia. The most important clinical presentation is neurological abnormalities. The severity of UCD is correlated to extent of hyperammonemia. Early diagnosis and treatment are essential for successful patient outcome. Various modalities of treatment have been recommended; namely, treatment aimed at reducing ammonia level, including drugs like sodium benzoate and sodium phenyl butyrate, neuroprotective strategies, low protein diet, liver transplantation and hepatocyte transplantation. Molecular diagnosis is important to identify the pathogenesis of these disorders as well as it helps in prognosis. This review intends to summarize the important aspects of molecular diagnostic studies on urea cycle disorders.