Inborn errors of metabolism

Loss-of-function and hypomorphic ECHS1 variants are associated with mitochondrial short-chain enoyl-CoA hydratase deficiency, an inborn error of valine metabolism. We report an 8-year-old boy with developmental delay, ataxia, hemiplegia, and hearing loss with abnormalities in the basal ganglia. Biochemical studies were essentially normal except for a persistent mildly elevated CSF alanine. This patient demonstrates an intermediate phenotype between a Leigh-like, early-onset presentation and paroxysmal exercise-induced dyskinesia...

Sialuria is a rare autosomal dominant inborn error of metabolism characterized by cytoplasmic accumulation and urinary excretion of gram quantities of free sialic acid due to failure of feedback inhibition of the rate-limiting enzyme in the sialic acid synthesis pathway, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE/MNK). To date, eight cases had been published worldwide, all with heterozygous missense variants at the allosteric site, specifically at Arginine 294 (formerly 263) and Arginine 297 (formerly 266) of GNE...

Homocystinuria is a genetic inborn error of metabolism due to the deficiency of cystathionine β-synthase resulting in increased serum homocysteine and methionine and decreased cysteine which predisposes affected individuals to arterial and venous thromboembolic phenomena. We present a case of homocystinuria who presented to us as a calcified right atrial mass during the evaluation for lower respiratory tract infection. Our case reveals an unusual mix of findings using imaging with multiple detector computed tomography and radiographs...

The treatment of some inborn metabolism errors requires cholesterol substitution therapy. Cholesterol plays a vital role in the human body. Therefore, the majority of cholesterol determination techniques are targeted to blood and blood serum. Nevertheless, cholesterol determination in food is important as well. In this paper, cholesterol determination using differential pulse voltammetry (DPV) in dairy products (e.g., milk, clotted cream, yogurt, butter, etc.) is reported with a novel nonenzymatic sensor based on diphosphonic acid of 1,4-diacetylglycoluril (DPADGU) as an electrode surface modifier...

Introduction: Phenyl ketonuria is an inborn error of amino acid metabolism resulting in excessive phenyl alanine levels in blood resulting in a spectrum of neurological defects. Patients and Methods: We retrospectively went through the records of patients diagnosed as Phenyl ketonuria in the last nine years in our team and patients who's data could be accessed were analyzed in detail. Details of laboratory tests, imaging clinical features, course were recorded. Observation: A total of 32 patients were identified in nine years of which data was available only for 15 patients...

This review offers an update on a group of inborn errors of metabolism causing severe epilepsy with the onset in pediatric age (but also other neurological manifestations such as developmental delay or movement disorders) with available effective or potentially effective treatments. The main pathogenic and clinical features and general recommendations for the diagnostic and therapeutic workup of the following disorders are discussed: vitamin B6 -dependent epilepsies, cerebral folate deficiency, congenital disorders of serine metabolism, biotinidase deficiency, inborn errors of creatine metabolism, molybdenum cofactor deficiency, and glucose transporter 1 deficiency...

INTRODUCTION: Newborn screening is important for early diagnosis and effective treatment of inborn errors of metabolism (IEM). In response to a 2008 coroners' report of a 14-year-old boy who died of an undiagnosed IEM, the OPathPaed service model was proposed. In the present study, we investigated the feasibility of the OPathPaed model for delivering expanded newborn screening in Hong Kong. In addition, health care professionals were surveyed on their knowledge and opinions of newborn screening for IEM...

Many anatomic pathology laboratories no longer have electron microscopy facilities. A retrospective review of autopsies was performed to identify cases of inborn errors of metabolism (IEM) and determine the contribution of electron microscopy in making the diagnosis in those cases. Over a period of 17 years, there were 900 perinatal and pediatric autopsies. There were 7 cases (1%) of IEM, including 4 cases of Pompe disease, 1 case of I-cell disease, 1 case of bile acid synthesis defect, and 1 case of mitochondrial disease (Leigh syndrome)...

Severe urea cycle defects (UCDs), organic acidemias (OAs), and maple syrup urine disease (MSUD) are life-threatening disorders presenting in the first days of life. Renal replacement therapy (RRT) is an emergency option in affected newborns, mostly performed as ultima ratio. We report our 10-year experience using emergency RRT in newborns with UCDs, OAs, and MSUD. Twelve newborns (8 with UCDs, 2 with methylmalonic acidemia, and 2 with MSUD) underwent emergency RRT. The overall survival rate to RRT was 58.3%...

PURPOSE: We propose a nosology for inborn errors of metabolism that builds on their recent redefinition. METHODS: We established a strict definition of criteria to develop a self-consistent schema for inclusion of a disorder into the nosology. RESULTS: We identified 1015 well-characterized inborn errors of metabolism described in the literature. In addition, there are 111 less well-characterized conditions that may be inborn errors but do not meet strict criteria for inclusion in the current nosology...

Neonatal convulsions are the most frequent form of expression of neurological pathology in the neonatal period. They represent a neurological emergency and thus require urgent diagnosis and treatment, as they are associated with a high risk of neonatal mortality or adverse neurological prognosis. Most neonatal convulsions are symptomatic and secondary to an identifiable causation. The causes vary widely. In this review we describe the electroclinical and aetiological aspects, and we also analyse the process of diagnosing the main epileptic syndromes in newborn infants...

In the last recent years, the -omics era has already transformed child neurology. Next generation sequencing (NGS) has identified many novel disease causing genes and phenotypes. While genetics is of great importance as a diagnostic tool, it is less helpful when it comes to a comprehensive understanding of mechanisms of brain dysfunction. Child neurologists are at high risk of being lost in genomics if they do not face the necessity of a new approach in their clinical practice. The large amount of data provided by NGS is just one more element in a complex puzzle...

Until recently, inborn errors of metabolism (IEM) were considered a pediatric specialty, as emphasized by the term "inborn," and the concept of adult onset IEM has only very recently reached the adult medical community. Still, an increasing number of adult onset IEM have now been recognized, as new metabolomics and molecular diagnostic techniques have become available. Here, we discuss possible mechanisms underlying phenotypic variability in adult versus children with IEM. Specifically, phenotypic severity and age of onset are expected to be modulated by differences in residual protein activity possibly driven by various genetic factors...

Compared to sites in protein-coding sequences many more targets undergoing adenosine to inosine (A-to-I) RNA editing were discovered in non-coding regions of human cerebral transcripts, particularly in genetic transposable elements called retrotransposons. We review here the interaction mechanisms of RNA editing and retrotransposons and their impact on normal function and human neurological diseases. Exemplarily, A-to-I editing of retrotransposons embedded in protein-coding mRNAs can contribute to protein abundance and function via circular RNA formation, alternative splicing, and exonization or silencing of retrotransposons...

Synaptic functions have long been thought to be driven by proteins, especially the SNARE complex, contrasting with a relatively passive role for lipids constituting cell membranes. It is now clear that not only lipids, i.e. glycerophospholipids, sphingolipids and sterols, play a determinant role in the dynamics of synaptic membranes but they also actively contribute to the endocytosis and exocytosis of synaptic vesicles in conjunction with synaptic proteins. On the other hand, a growing number of inborn errors of metabolism affecting the nervous system have been related to defects in the synthesis and remodelling of fatty acids, phospholipids and sphingolipids...

The ability to differentiate human induced pluripotent stem cells (iPSCs) into hepatocyte-like cells (HLCs) provides new opportunities to study inborn errors in hepatic metabolism. However, to provide a platform that supports the identification of small molecules that can potentially be used to treat liver disease, the procedure requires a culture format that is compatible with screening thousands of compounds. Here, we describe a protocol using completely defined culture conditions, which allow the reproducible differentiation of human iPSCs to hepatocyte-like cells in 96-well tissue culture plates...

Metabolome, the ultimate functional product of the genome, can be studied through identification and quantification of small molecules. The global metabolome influences the individual phenotype through clinical and environmental interventions. Metabolomics has become an integral part of clinical research and allowed for another dimension of better understanding of disease pathophysiology and mechanism. More than 95% of the clinical biochemistry laboratory routine workload is based on small molecular identification, which can potentially be analyzed through metabolomics...

Purine nucleotides are involved in a variety of cellular functions, such as energy storage and transfer, and signalling, in addition to being the precursors of nucleic acids and cofactors of many biochemical reactions. They can be generated through two separate pathways, the de novo biosynthesis pathway and the salvage pathway. De novo purine biosynthesis leads to the formation of IMP, from which the adenylate and guanylate pools are generated by two additional steps. The salvage pathways utilize hypoxanthine, guanine and adenine to generate the corresponding mononucleotides...

Two inborn errors of coenzyme A (CoA) metabolism are responsible for distinct forms of neurodegeneration with brain iron accumulation (NBIA), a heterogeneous group of neurodegenerative diseases having as a common denominator iron accumulation mainly in the inner portion of globus pallidus. Pantothenate kinase-associated neurodegeneration (PKAN), an autosomal recessive disorder with progressive impairment of movement, vision and cognition, is the most common form of NBIA and is caused by mutations in the pantothenate kinase 2 gene (PANK2), coding for a mitochondrial enzyme, which phosphorylates vitamin B5 in the first reaction of the CoA biosynthetic pathway...

Although individual cases of inherited metabolic disorders are rare, overall they account for a substantial number of disorders affecting the central nervous system. Organic acidemias and aminoacidopathies include a variety of inborn errors of metabolism that are caused by defects in the intermediary metabolic pathways of carbohydrates, amino acids, and fatty acid oxidation. These defects can lead to the abnormal accumulation of organic acids and amino acids in multiple organs, including the brain. Early diagnosis is mandatory to initiate therapy and prevent permanent long-term neurologic impairments or death...