An international classification of inherited metabolic disorders (ICIMD).

Several initiatives at establishing a classification of inherited metabolic disorders have been published previously, some focusing on pathomechanisms, others on clinical manifestations, while yet another attempted a simplified approach of a comprehensive nosology. Some of these classifications suffered from shortcomings, such as lack of a mechanism for continuous update in light of a rapidly evolving field, or lack of widespread input from the metabolic community at large. Our classification-the International Classification of Inherited Metabolic Disorders, or International Classification of Inborn Metabolic Disorders (ICIMD)-includes 1450 disorders, and differs from prior approaches in that it benefited from input by a large number of experts in the field, and was endorsed by major metabolic societies around the globe. Several criteria such as pathway involvement and pathomechanisms were considered. The main purpose of the hierarchical, group-based approach of the ICIMD is an improved understanding of the interconnections between many individual conditions that may share functional, clinical, and diagnostic features. The ICIMD aims to include any primary genetic condition in which alteration of a biochemical pathway is intrinsic to specific biochemical, clinical, and/or pathophysiological features. As new disorders are discovered, we will seek the opinion of experts in the advisory board prior to inclusion in the appropriate group of the ICIMD, thus guaranteeing the continuing relevance of this classification via regular curation and expert advice.

Rethinking fibrinogen storage disease of the liver: ground glass and globular inclusions do not represent a congenital metabolic disorder but acquired collective retention of proteins.

Three types of intracytoplasmic inclusions immunoreactive to fibrinogen are collectively diagnosed as hepatic fibrinogen storage disease. This study aimed to better characterize ground glass (type II) and globular (type III) fibrinogen inclusions by the pathological examination of 3 cases and a literature review. Three adults (age: 32-64 years; male/female = 2:1) were unexpectedly found to have fibrinogen-positive ground glass changes (type II inclusions) by liver needle biopsy, against a background of acute hepatitis E, resolving acute cholangitis, or severe lobular hepatitis of unknown etiology. One patient also had fibrinogen-positive intracytoplasmic globules (type III inclusions) in the first biopsy, but they were not present in a second biopsy. None had coagulation abnormalities or hypofibrinogenemia. On immunostaining, both inclusions were strongly positive for not only fibrinogen but also C-reactive protein and C4d. Ultrastructurally, ground glass changes corresponded to membrane-bound cytoplasmic inclusions containing amorphous, granular material. The pathological features of type II fibrinogen inclusions were identical to those of pale bodies in hepatocellular carcinoma. The literature review suggested that type I fibrinogen inclusions characterized by a polygonal appearance are strongly associated with mutations in fibrinogen genes, coagulopathy, and family history, whereas type II/III inclusions are immunoreactive to multiple proteins and typically develop in cases of other unrelated liver diseases. In conclusion, type II and III fibrinogen inclusions do not represent a true hereditary storage disease but instead the collective retention of multiple proteins. Given the lack of clinical significance, a less specific name (e.g., pale body) may be more appropriate for those inclusions.

Incidencia de errores innatos del metabolismo y otros trastornos detectados en un programa de cribado metabólico neonatal ampliado de un grupo mexicano de hospitales / Incidence of inborn errors of metabolism and other diseases detected in a newborn screening program within a group of Mexican private hospitals

INTRODUCCIÓN: La detección de errores innatos del metabolismo (EIM), endocrinopatías, hemoglobinopatías y otros trastornos por medio del cribado metabólico neonatal es una iniciativa de salud mundial que comenzó hasta el año 1973 en México. La incidencia nacional de este grupo de enfermedades es incierta debido a la falta de programas de cribado metabólico neonatal ampliado (CMNA), aunada a la carencia de publicaciones relacionadas. Para el presente manuscrito, la incidencia de EIM en el noreste de México se estima a partir de un programa de CMNA en hospitales privados del Grupo Christus Muguerza. MATERIAL Y MÉTODOS: El estudio fue retrospectivo e incluyó la revisión de resultados de 19.768 recién nacidos (RN), obtenidos de marzo de 2006 a febrero de 2017. RESULTADOS: El programa de CMNA detectó a 60 RN con algún EIM u otro trastorno y 104 fueron identificados como heterocigotos, presentando una incidencia de 30,4 y 52,7 por cada 10.000 RN, respectivamente. El diagnóstico más frecuente fue la deficiencia de glucosa-6-fosfato deshidrogenasa (G6PD); y en el caso de los heterocigotos, las hemoglobinopatías. La combinación de tecnologías en el cribado resultó en una especificidad del 99,95%, una sensibilidad cercana al 100% y un valor predictivo positivo del 86,96%. CONCLUSIONES: Los programas de CMNA ofrecen la posibilidad de detectar y confirmar un diagnóstico temprano para ofrecer un tratamiento específico, en combinación con un asesoramiento genético. Por otro lado, estos resultados proporcionan una estimación de la incidencia de los EIM, endocrinopatías, hemoglobinopatías y otros trastornos en un grupo de hospitales privados en México

INTRODUCTION: The detection of inborn errors of metabolism (IEM), endocrinopathies, hemoglobinopathies, and other disorders through newborn screening (NBS) is a global health initiative that began until 1973 in Mexico. The national incidence of this group of diseases is uncertain due to the lack of NBS programs and related publications. For the present manuscript, the incidence of a specific group of IEM, endocrinopathies, hemoglobinopathies, and other disorders in newborns was estimated from an NBS program implemented in a private group of hospitals part of Grupo Christus Muguerza located northeast of Mexico. MATERIAL AND METHODS: This retrospective study included the examination of 19,768 newborns' results obtained from the NBS program from March 2006 to February 2017. RESULTS: The NBS program found 60 newborns with an IEM or other disorder and 104 were identified as carriers, with an incidence of 30.4 and 52.7 per 10,000 newborns, respectively. The most frequent diagnosis was glucose-6-phosphate dehydrogenase deficiency (G6PD); and in the case of carriers, were hemoglobinopathies. The combination of screening technologies showed a specificity of 99.95%, a sensitivity close to 100%, and a positive predictive value of 86.96%. CONCLUSIONS: The benefit of an NBS program is to stablish an early diagnosis to offer prompt treatment and proper genetic counseling. Furthermore, these results provide an estimation of IEM, endocrinopathies, hemoglobinopathies, and other disorders incidence in a group of private hospitals in Mexico

Proposal for a simplified classification of IMD based on a pathophysiological approach: A practical guide for clinicians.

In view of the rapidly expanding number of IMD discovered by next generation sequencing, we propose a simplified classification of IMD that mixes elements from a clinical diagnostic perspective and a pathophysiological approach based on three large categories. We highlight the increasing importance of complex molecule metabolism and its connection with cell biology processes. Small molecule disorders have biomarkers and are divided in two subcategories: accumulation and deficiency. Accumulation of small molecules leads to acute or progressive postnatal "intoxication", present after a symptom-free interval, aggravated by catabolism and food intake. These treatable disorders must not be missed! Deficiency of small molecules is due to impaired synthesis of compounds distal to a block or altered transport of essential molecules. This subgroup shares many clinical characteristics with complex molecule disorders. Complex molecules (like glycogen, sphingolipids, phospholipids, glycosaminoglycans, glycolipids) are poorly diffusible. Accumulation of complex molecules leads to postnatal progressive storage like in glycogen and lysosomal storage disorders. Many are treatable. Deficiency of complex molecules is related to the synthesis and recycling of these molecules, which take place in organelles. They may interfere with fœtal development. Most present as neurodevelopmental or neurodegenerative disorders unrelated to food intake. Peroxisomal disorders, CDG defects of intracellular trafficking and processing, recycling of synaptic vesicles, and tRNA synthetases also belong to this category. Only few have biomarkers and are treatable. Disorders involving primarily energy metabolism encompass defects of membrane carriers of energetic molecules as well as cytoplasmic and mitochondrial metabolic defects. This oversimplified classification is connected to the most recent available nosology of IMD.

Metabolic liver diseases presenting with neonatal cholestasis: at the crossroad between old and new paradigms.

Metabolic liver diseases (MLD) are an important group of disorders presenting with neonatal cholestasis (NC). The spectrum of liver involvement is wide and the presumptive diagnosis is traditionally based on clinical and laboratory findings. Recently, next-generation sequencing (NGS) panels have emerged as an appealing tool to diagnose neonatal/infantile cholestatic disorders. The aim of this study was to identify clinical phenotypes of liver injury and contribute to find a diagnostic methodology that integrates new molecular diagnostic tools. We retrospectively analyzed the clinical and biochemical features of 16 patients with MLD and NC. Patients were categorized into three groups: A-NC with liver failure (N = 8): tyrosinemia type I (n = 2), classic galactosemia (n = 5), mitochondrial DNA depletion syndrome (n = 1); B-NC evolving with chronic liver disease (N = 5): argininemia (n = 2); mitochondrial cytopathy (n = 1); congenital disorders of glycosylation type Ia (n = 1); Zellweger syndrome (n = 1); and C-transient NC (N = 3): Niemann-Pick type C (n = 2), citrullinemia type II (n = 1).Conclusion: MLD presenting with NC can be categorized into three main clinical phenotypes of liver injury. We highlight transient NC as a clue for MLD that must be pursued. New molecular diagnostic tools can play a key role, but application criteria must be established to make them cost-effective. What is Known: • Metabolic liver diseases are an important group of disorders presenting with neonatal cholestasis. • The diagnostic approach is challenging and traditionally based on clinical and laboratory findings. Next-generation sequencing is a recent and rapidly developing tool in pediatric hepatology. What is New: • We provide a liver-targeted characterization of metabolic liver diseases presenting with neonatal cholestasis, categorizing them into three clinical phenotypes that may narrow the diagnostic possibilities. • A clinical decision-making algorithm is proposed, in which the NGS technology is integrated.

A proposed nosology of inborn errors of metabolism.

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. CONCLUSION: We provide a master list of all currently recognized inborn errors of metabolism grouped according to their pathophysiological basis, with the hope of setting a standard against which new errors should be defined, as well as to promote awareness and foster collaboration in the area. With the rapid advances in the field of genetics in recent years, it is likely that this nosology will need to be updated in the near future, a process that will benefit from broader input and collaboration of experts in the field to improve future versions of the proposed classification.

Repercussions of inborn errors of immunity on growth.

OBJECTIVES: This study aimed to review the literature on the repercussions of the different inborn errors of immunity on growth, drawing attention to the diagnosis of this group of diseases in patients with growth disorders, as well as to enable the identification of the different causes of growth disorders in patients with inborn errors of immunity, which can help in their treatment. DATA SOURCES: Non-systematic review of the literature, searching articles since 2000 in PubMed with the terms "growth", "growth disorders", "failure to thrive", or "short stature" AND "immunologic deficiency syndromes", "immune deficiency disease", or "immune deficiency" NOT HIV. The Online Mendelian Inheritance in Man (OMIN) database was searched for immunodeficiencies and short stature or failure to thrive. DATA SUMMARY: Inborn errors of immunity can affect growth in different ways, and some of them can change growth through multiple simultaneous mechanisms: genetic syndromes; disorders of the osteoarticular system; disorders of the endocrine system; reduction in caloric intake; catabolic processes; loss of nutrients; and inflammatory and/or infectious conditions. CONCLUSIONS: The type of inborn errors of immunity allows anticipating what type of growth disorder can be expected. The type of growth disorder can help in the diagnosis of clinical conditions related to inborn errors of immunity. In many inborn errors of immunity, the causes of poor growth are mixed, involving more than one factor. In many cases, impaired growth can be adjusted with proper inborn errors of immunity treatment or proper approach to the mechanism of growth impairment.

Repercussions of inborn errors of immunity on growth / Repercussões dos erros inatos da imunidade sobre o crescimento

Abstract Objectives: This study aimed to review the literature on the repercussions of the different inborn errors of immunity on growth, drawing attention to the diagnosis of this group of diseases in patients with growth disorders, as well as to enable the identification of the different causes of growth disorders in patients with inborn errors of immunity, which can help in their treatment. Data sources: Non-systematic review of the literature, searching articles since 2000 in PubMed with the terms "growth", "growth disorders", "failure to thrive", or "short stature" AND "immunologic deficiency syndromes", "immune deficiency disease", or "immune deficiency" NOT HIV. The Online Mendelian Inheritance in Man (OMIN) database was searched for immunodeficiencies and short stature or failure to thrive. Data summary: Inborn errors of immunity can affect growth in different ways, and some of them can change growth through multiple simultaneous mechanisms: genetic syndromes; disorders of the osteoarticular system; disorders of the endocrine system; reduction in caloric intake; catabolic processes; loss of nutrients; and inflammatory and/or infectious conditions. Conclusions: The type of inborn errors of immunity allows anticipating what type of growth disorder can be expected. The type of growth disorder can help in the diagnosis of clinical conditions related to inborn errors of immunity. In many inborn errors of immunity, the causes of poor growth are mixed, involving more than one factor. In many cases, impaired growth can be adjusted with proper inborn errors of immunity treatment or proper approach to the mechanism of growth impairment.

Resumo Objetivos: Revisão da literatura sobre as repercussões dos diferentes erros inatos da imunidade sobre o crescimento, chamar a atenção para o diagnóstico desse grupo de doenças em pacientes que apresentem desordens do crescimento, assim como permitir que se identifiquem as diferentes causas de alterações do crescimento em pacientes com erros inatos da imunidade, o que pode auxiliar em seu manejo. Fonte dos dados: Revisão não sistemática da literatura, com busca de artigos desde 2000 no Pubmed com os termos "growth" ou "growth disorders" ou "failure to thrive" ou "short stature" AND "immunologic deficiency syndromes" ou "immune deficiency disease" ou "imune deficiency" NOT HIV. E buscas na base OMIN (Online Mendelian Inheritance in Man) por imunodeficiências e baixa estatura ou falha no crescimento ("failure to thrive"). Síntese dos dados: Há diferentes modos pelos quais os erros inatos da imunidade podem afetar o crescimento e alguns deles podem alterar o crescimento por múltiplos mecanismos simultâneos: síndromes genéticas; afecções do aparelho osteoarticular; afecções do sistema endócrino; redução de aporte calórico; processos catabólicos: perda de nutrientes, assim como afecções inflamatórias e/ou infecciosas. Conclusões: O tipo de erros inatos da imunidade permite prever que tipo de alteração no crescimento devemos esperar. O tipo de alteração no crescimento pode auxiliar no diagnóstico de condições clínicas associadas aos erros inatos da imunidade. Em muitos erros inatos da imunidade, as causas do crescimento deficiente são mistas, envolvem mais de um fator. Em muitos casos, o prejuízo do crescimento pode ser corrigido com o adequado tratamento dos erros inatos da imunidade ou adequada abordagem do mecanismo que causa o prejuízo do crescimento.

Cellular neurometabolism: a tentative to connect cell biology and metabolism in neurology.

It has become increasingly evident that inborn errors of metabolism (IEMs) are particularly prevalent as diseases of the nervous system and that a broader, more inclusive definition of IEM is necessary. In fact, as long as biochemistry is involved, any kind of monogenic disease can become an IEM. This new, extended definition includes new categories and mechanisms, and as a general trend will go beyond a single biochemical pathway and/or organelle, and will appear as a connection of multiple crossroads in a system biology approach.From one side, a simplified and updated classification of IEM is presented that mixes elements from the diagnostic approach with pathophysiological considerations into three large categories based on the size of molecules ("small and simple" or "large and complex") and their implication in energy metabolism. But from another side, whatever their size, metabolites involved in IEM may behave in the brain as signalling molecules, structural components and fuels, and many metabolites have more than one role. Neurometabolism is becoming more relevant, not only in relation to these new categories of diseases but also as a necessary way to explain the mechanisms of brain damage in classically defined categories of IEM. Brain metabolism, which has been largely disregarded in the traditional approach to investigating and treating neurological diseases, is a major clue and probably the next imminent "revolution" in neurology and neuroscience. Biochemistry (metabolism) and cell neurobiology need to meet. Additionally, the brain should be studied as a system (connecting different levels of complexity).

Exchange of Partial Liver Transplantation Between Children with Different Non-Cirrhotic Metabolic Liver Diseases: How Do We Arrive There?

Hepatic-based metabolic disorders are characterized by an enzyme deficiency expressed solely or mainly in the liver. They are divided into cirrhotic or non-cirrhotic metabolic liver diseases (NCMLDs), and most of them can be treated by liver transplantation. Because the livers with NCMLDs are usually structurally and functionally normal, the primary aim of the liver graft is to support the deficient enzymes rather than maintaining liver functions. Hence, we hypothesize that the exchange of partial liver grafts by the technique of auxiliary partial orthotopic liver transplantation (APOLT) between patients with 2 different NCMLDs may be feasible to replace the deficient enzymes in each patient. This hypothesis is based on the following conditions: (i) the patients have no chance of undergoing timely liver transplantation, (ii) the symptoms of each NCMLD may be alleviated after exchanging partial liver grafts, and (iii) each graft is anatomically appropriate for APOLT. In addition, we evaluate it with a focus on selection of cases, designing of graft sizes, and surgical techniques for reciprocal APOLT.

Targeted Next Generation Sequencing in Patients with Inborn Errors of Metabolism.

BACKGROUND: Next-generation sequencing (NGS) technology has allowed the promotion of genetic diagnosis and are becoming increasingly inexpensive and faster. To evaluate the utility of NGS in the clinical field, a targeted genetic panel approach was designed for the diagnosis of a set of inborn errors of metabolism (IEM). The final aim of the study was to compare the findings for the diagnostic yield of NGS in patients who presented with consistent clinical and biochemical suspicion of IEM with those obtained for patients who did not have specific biomarkers. METHODS: The subjects studied (n = 146) were classified into two categories: Group 1 (n = 81), which consisted of patients with clinical and biochemical suspicion of IEM, and Group 2 (n = 65), which consisted of IEM cases with clinical suspicion and unspecific biomarkers. A total of 171 genes were analyzed using a custom targeted panel of genes followed by Sanger validation. RESULTS: Genetic diagnosis was achieved in 50% of patients (73/146). In addition, the diagnostic yield obtained for Group 1 was 78% (63/81), and this rate decreased to 15.4% (10/65) in Group 2 (X2 = 76.171; p < 0.0001). CONCLUSIONS: A rapid and effective genetic diagnosis was achieved in our cohort, particularly the group that had both clinical and biochemical indications for the diagnosis.

[Food Allergy and Intolerance : Distinction, Definitions and Delimitation]. / Nahrungsmittelallergien und andere -unverträglichkeiten : Bedeutung, Begriffe und Begrenzung.

Immunologically mediated hypersensitivity to foods is defined as food allergy, mainly due to immunglobulins of class E (IgE) triggering immediate reactions (type I hypersensitivity) with possible involvement of mucosa, skin, airways, intestinal tract, and the vascular system. Primary food allergy is based on (early) IgE sensitization against animal (e. g., cow's milk, hen's eggs) or plant proteins (e. g. peanut, hazelnut or wheat). In the case of secondary food allergies, IgE against pollen proteins (e. g., birch) reacts to structurally related food proteins (with cross-reactions to stone and pit fruits). Non-immunological food intolerance reactions are mostly based on carbohydrate malassimilation (e. g., lactose intolerance, fructose malabsorption) and are rarely due to pseudo-allergies (e. g., flavors, dyes, preservatives) primarily in patients with chronic urticaria. Common intestinal symptoms are mainly due to functional disorders (e. g., irritable bowel disease), rarely because of inflammatory intestinal diseases (e. g., celiac disease). Histamine intolerance, gluten hypersensitivity, and so-called food type III hypersensitivities are controversial diagnoses. The aforementioned disease entities/models are of variable importance for the affected individuals, the public health system, and society in general.

[Inborn errors of metabolism in adult neurology]. / Les maladies métaboliques héréditaires en neurologie adulte.

Inborn errors of metabolism (IEM) are caused by mutations in genes coding for enzymes and other proteins involved in cell metabolism. Many IEM can be treated effectively. Although IEM have usually been considered pediatric diseases, they can present at any age, mostly with neurological and psychiatric symptoms, and therefore constitute an integral subspeciality of neurology. However, although they are increasingly being recognized, IEM remain rare, and the care for patients should be optimized in specialized reference centers. Since the number of different diseases is very large, the diagnostic approach needs to be rigorous, starting at the clinics and calling upon the additional help of neuroradiology, biochemistry and molecular biology. In practice, it is important for the neurologist to recognize: (1) when to start suspecting an IEM; and (2) how to correlate a given clinical presentation with one of the five major groups of diseases affecting the nervous system. These five groups may be classified as: (a) energy metabolism disorders such as respiratory chain disorders, pyruvate dehydrogenase deficiency, GLUT1 deficiency, fatty-acid ß-oxidation defects, and disorders involving key cofactors such as electron transfer flavoprotein, thiamine, biotin, riboflavin, vitamin E and coenzyme Q10; (b) intoxication syndromes such as porphyrias, urea-cycle defects, homocystinurias, organic acidurias and amino acidopathies; (c) lipid-storage disorders such as lysosomal storage disorders (Krabbe disease, metachromatic leukodystrophy, Niemann - Pick disease type C, Fabry disease and Gaucher's disease), peroxisomal disorders (adrenomyeloneuropathy, Refsum disease, disorders of pristanic acid metabolism, peroxisome biogenesis disorders), Tangier disease and cerebrotendinous xanthomatosis; (d) metal-storage diseases such as iron, copper and manganese metabolic disorders; and (e) neurotransmitter metabolism defects, including defects of serotonin, dopamine and glycine metabolism.

Inborn errors of metabolism with 3-methylglutaconic aciduria as discriminative feature: proper classification and nomenclature.

Increased urinary 3-methylglutaconic acid excretion is a relatively common finding in metabolic disorders, especially in mitochondrial disorders. In most cases 3-methylglutaconic acid is only slightly elevated and accompanied by other (disease specific) metabolites. There is, however, a group of disorders with significantly and consistently increased 3-methylglutaconic acid excretion, where the 3-methylglutaconic aciduria is a hallmark of the phenotype and the key to diagnosis. Until now these disorders were labelled by roman numbers (I-V) in the order of discovery regardless of pathomechanism. Especially, the so called "unspecified" 3-methylglutaconic aciduria type IV has been ever growing, leading to biochemical and clinical diagnostic confusion. Therefore, we propose the following pathomechanism based classification and a simplified diagnostic flow chart for these "inborn errors of metabolism with 3-methylglutaconic aciduria as discriminative feature". One should distinguish between "primary 3-methylglutaconic aciduria" formerly known as type I (3-methylglutaconyl-CoA hydratase deficiency, AUH defect) due to defective leucine catabolism and the--currently known--three groups of "secondary 3-methylglutaconic aciduria". The latter should be further classified and named by their defective protein or the historical name as follows: i) defective phospholipid remodelling (TAZ defect or Barth syndrome, SERAC1 defect or MEGDEL syndrome) and ii) mitochondrial membrane associated disorders (OPA3 defect or Costeff syndrome, DNAJC19 defect or DCMA syndrome, TMEM70 defect). The remaining patients with significant and consistent 3-methylglutaconic aciduria in whom the above mentioned syndromes have been excluded, should be referred to as "not otherwise specified (NOS) 3-MGA-uria" until elucidation of the underlying pathomechanism enables proper (possibly extended) classification.

Inborn errors of metabolism causing epilepsy.

Seizures may be the first and the major presenting feature of an inborn error of metabolism (IEM), for example in a neonate with pyridoxine-dependent epilepsy. In other IEMs, seizures may be preceded by other major symptoms: by a reduced level of consciousness in a child with an organic acidaemia or urea cycle defect; or by loss of skills, progressive weakness, ataxia, and upper motor signs in a child with a lysosomal storage disorder or peroxisomal leukodystrophy. This review concentrates on those IEMs for which specific treatment is available. The common metabolic causes of seizures vary according to the age at presentation. Features from the history, examination, imaging, and first line biochemical investigations can all provide clues to an inborn error. This review attempts to delineate these and to provide a guide to the specific tests that can be used to make the diagnosis of disorders with specific treatment.

[Clinical presentation of inborn metabolic diseases in the neonatal period]. / Signes néonatals des maladies héréditaires du métabolisme.

Inborn metabolic diseases (IMDs) that can start in the neonatal period include various defects in numerous metabolic pathways. Such diseases are due to the genetic deficiency of an enzyme or a transporter. From a physiopathological point of view, the metabolic disorders can be divided into 3 diagnostically useful groups of diseases. The first group is due to the accumulation of endogenous toxic metabolites and includes inborn errors of amino acid metabolism, organic acidemias, urea cycle disorders, and sugar intolerances. The second one includes IMDs of intermediary metabolism causing a disturbance in energy production or utilization resulting from a defect in the liver, the muscles, the myocardium, or the brain (fatty acid oxidation defects, congenital lactic acidosis, etc.). The third group includes diseases that disturb the synthesis or the catabolism of complex molecules (lysosomal or peroxisomal disorders, etc.). IMDs are individually rare, but collectively numerous. Therefore, it is difficult to acquire extensive experience in the management of these diseases. However, the neonate has a limited repertoire of responses to severe illness and, at first, presents with nonspecific symptoms that could be easily attributed to infection or some other common cause. An IMD must be suspected in all situations of neonatal distress for which there is no apparent reason and that does not respond to symptomatic therapy. The priority is given to IMDs that are amenable to treatment, and emergency management has to be scheduled as soon as the diagnosis is suspected, even if the precise diagnosis is still unknown. In fact, emergency treatment must be undertaken in parallel with metabolic investigations, to prevent any delay in the management of the disease. The neonatologist must be able to recognize the neonatal distresses that suggest the possibility of an IMD. In such situations, an adequate diagnostic approach can be based on the proper use of only a few screening tests, which will also be useful to schedule adequate emergency treatment.

Infantile spasms (West syndrome) in children with inborn errors of metabolism: a review of the literature.

West syndrome (infantile spasms) is an epileptic encephalopathy that includes psychomotor deterioration. In rare cases, it is due to an inherited, progressive metabolic disease. More than 25 inborn errors of metabolism have been considered etiologic or predisposing factors for infantile spasms. This is a review of the literature on reported cases of children diagnosed with a metabolic disease who developed infantile spasms. This article presents in brief the most frequent inborn errors of metabolism that have been associated with West syndrome and also illustrates the importance of screening for inborn errors of metabolism in infantile spasms.