Cognitive stimulation has potential for brain activation in individuals with Rett syndrome.

BACKGROUND: Knowledge regarding neuropsychological training in Rett syndrome (RS) is scarce. The aim of this study was to assess the outcome and the duration of the effect of cognitive stimulation on topographic electroencephalography (EEG) data in RS. METHODS: Twenty female children diagnosed with RS were included in the analysis. Girls with RS conducted a cognitive task using an eye-tracker designed to evaluate access and choice skills. EEG data were acquired during the experimental procedure including two 10-min baseline stages before and after the task. Topographical changes of several EEG spectral markers including absolute and relative powers, Brain Symmetry Index and entropy were assessed. RESULTS: Topographic significance probability maps suggested statistical decreases on delta activity and increases on beta rhythm associated with the cognitive task. Entropy increased during and after the task, likely related to more complex brain activity. A significant positive interaction was obtained between Brain Symmetry Index and age showing that the improvement of interhemispheric symmetry was higher in younger girls (5-10 years). CONCLUSIONS: According to our findings, significant alterations of brain rhythms were observed during and after cognitive stimulation, suggesting that cognitive stimulation may have effects on brain activity beyond the stimulation period. Finally, our promising results also showed an increase brain symmetry that was especially relevant for the younger group. This could suggest an interaction of the eye-tracking cognitive task; however, further studies in this field are needed to assess the relation between brain asymmetries and age.

Mitochondrial response to the BCKDK-deficiency: Some clues to understand the positive dietary response in this form of autism.

Mutations on the mitochondrial-expressed Branched Chain α-Keto acid Dehydrogenase Kinase (BCKDK) gene have been recently associated with a novel dietary-treatable form of autism. But, being a mitochondrial metabolism disease, little is known about the impact on mitochondrial performance. Here, we analyze the mitochondrial response to the BCKDK-deficiency in patient's primary fibroblasts by measuring bioenergetics, ultra-structural and dynamic parameters. A two-fold increase in superoxide anion production, together with a reduction in ATP-linked respiration and intracellular ATP levels (down to 60%) detected in mutants fibroblasts point to a general bioenergetics depletion that could affect the mitochondrial dynamics and cell fate. Ultrastructure analysis of BCKDK-deficient fibroblasts shows an increased number of elongated mitochondria, apparently associated with changes in the mediator of inner mitochondria membrane fusion, GTPase OPA1 forms, and in the outer mitochondrial membrane, mitofusin 2/MFN2. Our data support a possible hyperfusion response of BCKDK-deficient mitochondria to stress. Cellular fate also seems to be affected as these fibroblasts show an altered proportion of the cells on G0/G1 and G2/M phases. Knockdown of BCKDK gene in control fibroblasts recapitulates most of these features. Same BCKDK-knockdown in a MSUD patient fibroblasts unmasks the direct involvement of the accelerated BCAAs catabolism in the mitochondrial dysfunction. All these data give us a clue to understand the positive dietary response to an overload of branched-chain amino acids. We hypothesize that a combination of the current therapeutic option with a protocol that considers the oxidative damage and energy expenditure, addressing the patients' individuality, might be useful for the physicians.

Joubert syndrome: a model for untangling recessive disorders with extreme genetic heterogeneity.

BACKGROUND: Joubert syndrome (JS) is a recessive neurodevelopmental disorder characterised by hypotonia, ataxia, cognitive impairment, abnormal eye movements, respiratory control disturbances and a distinctive mid-hindbrain malformation. JS demonstrates substantial phenotypic variability and genetic heterogeneity. This study provides a comprehensive view of the current genetic basis, phenotypic range and gene-phenotype associations in JS. METHODS: We sequenced 27 JS-associated genes in 440 affected individuals (375 families) from a cohort of 532 individuals (440 families) with JS, using molecular inversion probe-based targeted capture and next-generation sequencing. Variant pathogenicity was defined using the Combined Annotation Dependent Depletion algorithm with an optimised score cut-off. RESULTS: We identified presumed causal variants in 62% of pedigrees, including the first B9D2 mutations associated with JS. 253 different mutations in 23 genes highlight the extreme genetic heterogeneity of JS. Phenotypic analysis revealed that only 34% of individuals have a 'pure JS' phenotype. Retinal disease is present in 30% of individuals, renal disease in 25%, coloboma in 17%, polydactyly in 15%, liver fibrosis in 14% and encephalocele in 8%. Loss of CEP290 function is associated with retinal dystrophy, while loss of TMEM67 function is associated with liver fibrosis and coloboma, but we observe no clear-cut distinction between JS subtypes. CONCLUSIONS: This work illustrates how combining advanced sequencing techniques with phenotypic data addresses extreme genetic heterogeneity to provide diagnostic and carrier testing, guide medical monitoring for progressive complications, facilitate interpretation of genome-wide sequencing results in individuals with a variety of phenotypes and enable gene-specific treatments in the future.

Cerebrospinal fluid synaptic proteins as useful biomarkers in tyrosine hydroxylase deficiency.

Tyrosine hydroxylase (TH) deficiency is an inborn error of dopamine biosynthesis and a cause of early parkinsonism. Two clinical phenotypes have been described. Type "B": early onset severe encephalopathy; type "A": later onset, less severe and better response to L-dopa. We aimed to study the expression of several key dopaminergic and gabaergic synaptic proteins in the cerebrospinal fluid (CSF) of a series of patients with TH deficiency and their possible relation with the clinical phenotype and response to L-DOPA. Dopamine transporter (DAT), D2-receptor and vesicular monoamine transporter (VMAT2) were measured in the CSF of 10 subjects with TH deficiency by Western blot analysis. In 3 patients, data of pre- and post-treatment with L-DOPA were available, and in one of them, GABA vesicular transporter was determined. Results were compared to an age-matched control population. The concentration of D2-receptors in CSF was significantly higher in patients with TH deficiency than in controls. Similarly, DAT and vesicular monoamine transporter type 2 were up-regulated. Studies performed before L-DOPA, and on L-DOPA therapy showed a paradoxical response with D2 receptor expression increase as L-Dopa doses and homovanillic concentration gradually raised in a B phenotype patient. The opposite results were found in two patients with A phenotype. However, this is a very small sample, and further studies are needed to conclude robust differences between phenotypes. Synaptic proteins are detectable in the CSF and their quantification can be useful for understanding the pathophysiology of neurotransmitter defects and potentially to adjust and personalize treatments in the future.

Parkinsonism and inborn errors of metabolism.

Parkinsonism is a frequent neurological syndrome in adulthood but is very rare in childhood. Early forms of Parkinsonism have many distinctive features as compared to Parkinsonism in adults. In fact, rather than Parkinsonism, the general concept "hypokinetic-rigid syndrome" (HRS) is more accurate in children. In general, the terms "dystonia-parkinsonism", "parkinsonism-plus", or "parkinsonism-like" are preferred to designate these forms of paediatric HRS. Inborn errors of metabolism (IEM) constitute an important group amongst the genetic causes of Parkinsonism at any age. The main IEM causing Parkinsonism are metal-storage diseases, neurotransmitter defects, lysosomal storage disorders and energy metabolism defects. IEM should not be neglected as many of them represent treatable causes of Parkinsonism. Here we review IEMs causing this neurological syndrome and propose diagnostic approaches depending on the age of onset and the associated clinical and neuroimaging features.

Clinical and biochemical outcome after hydroxocobalamin dose escalation in a series of patients with cobalamin C deficiency.

BACKGROUND: CblC deficiency produces a combination of methylmalonic aciduria (MMA) and homocystinuria (HCU), and is the most common error of cobalamin metabolism. Patients present a wide spectrum of symptoms, ranging from early severe multisystemic forms, to milder late-onset phenotypes. Cognitive and visual impairment are nearly constant. Hydroxocobalamin (OHCbl), betaine, folinic acid, levocarnitine and eventually dietary protein restriction are the main therapeutic approaches. Although early introduction of OHCbl is crucial, no standardized protocols regarding dose adaptation exist. No reports on long-term outcomes after high doses of this vitamin have been published. METHODS: In this study five patients with CblC deficiency (early severe forms) were treated with high doses of OHCbl for 18 to 30months. Clinical examinations, neurological assessment, and biochemical studies (plasma total homocysteine (tHcy), amino acids, hydroxocobalamin, and methylmalonic acid in urine) were periodically performed. RESULTS: Variable clinical and biochemical outcomes were observed in patients treated with high doses of OHCbl. The best biochemical response was observed in those children with the worse metabolic control. By contrast, those patients with a concentration of tHcy around 50µmol/l or less showed only minor changes. Clinically, a considerable improvement was observed in those patients with severe problems in communication, expressive language and behavior. CONCLUSIONS: According to our study, high OHCbl doses in CblC deficiency could have a greater benefit in those children with a prior history of suboptimal metabolic control, and also in those with severe neurological phenotypes. More specifically, we observed improvements in communication skills and behavior. These results should encourage further prospective trials to determine the optimal OHCbl regimen and to generate protocols and guidelines in this rare disorder.

Ancient origin of the CTH alelle carrying the c.200C>T (p.T67I) variant in patients with cystathioninuria.

Hereditary cystathioninuria is due to mutations in the CTH gene that encodes for cystathionase, a pyridoxal-5'-phosphate (PLP) dependent enzyme. To date, mutations in this gene have been described in 10 unrelated cystathioninuric patients. Enzyme assays have showed that mutated cystathionase exhibits lower activity than controls. As cystathioninuria is usually accompanied by a wide variety of symptoms, it has been questioned whether it is a disease or just a biochemical finding not associated with the clinical picture of these patients. This is the first report of Spanish patients with cystathioninuria and mild to severe neurological symptoms in childhood. After oral pyridoxine therapy biochemical parameters have normalized but clinical amelioration was not evident. All patients were homozygotes for the c.200C>T (p.T67I) variant which is the most prevalent inactivating mutation in the CTH gene. To further investigate the history of the alleles carrying the c.200C>T transition in Europe, we also constructed the haplotypes on the CTH locus in our Spanish patients as well as in a clinical series of cystathioninuric patients from the Czech Republic harboring the same nucleotide change. We suggest that the CTH p.T67I substitution could have an ancient common origin, which probably occurred in the Neolithic Era and spread throughout Europe.

Epilepsy and inborn errors of metabolism in children.

Epilepsy is a frequent symptom in inborn errors of metabolism, with virtually no specific seizure types or EEG signatures. It is most important to look quickly for those few inborn errors of metabolism in which specific therapies such as supplementation of cofactors or diets can make all the difference. If these investigations remain negative, epilepsy has to be treated with conventional antiepileptic drugs. Still, epilepsy is a potentially treatable symptom of many inborn errors of metabolism, and optimal treatment is of great importance for patients and their families.

Mental retardation and inborn errors of metabolism.

In countries where clinical phenylketonuria is detected by newborn screening inborn errors of metabolism are rare causes of isolated mental retardation. There is no international agreement about what type of metabolic tests must be applied in patients with unspecific mental retardation. However, and although infrequent, there are a number of inborn errors of metabolism that can present in this way. Because of the high recurrence risk and the possibility of specific therapies, guidelines need to be developed and adapted to different populations. The application of a universal protocol may result in a low diagnostic performance in individual ethnic populations. Consideration of associated signs (extraneurological manifestations, psychiatric signs, autistic traits, cerebellar dysfunction, epilepsy or dysmorphic traits) greatly improves the diagnostic fulfilment.

Inborn errors of metabolism and motor disturbances in children.

Motor disturbances are very common in paediatric neurology. Often families can be reassured that these are just variants of normal development. However, abnormal movements can also be the hallmark of severe brain dysfunction of different and complex origins. This review concentrates on motor disturbances as frequent and important symptoms of inborn errors of metabolism. A structured diagnostic approach is developed taking into account age-dependent physiological developments and pathophysiological responses of gross and fine motor functions. A series of investigations are presented with the primary aim of early diagnosis of treatable conditions. The correct recognition and differentiation of movement disorders (ataxia, rigid akinetic syndrome (Fparkinsonism_), dystonia, athetosis, tremor,and others), spasticity, and neuromuscular disorders, requires profound neurological expertise. A high level of suspicion and close interaction between paediatric neurologists and specialists in inborn errors of metabolism are indispensable to effectively and timely identify patients in whom motor disturbances are the presenting and/or main symptom of an inborn error.

[Adult-onset metabolic diseases]. / Enfermedades metabólicas de aparición en la edad adulta.

Inborn errors of metabolism (IEM) can have their onset in adolescence or in adulthood. Although it is difficult to contribute exact data on prevalence -because there are few studies in this respect, and IEM are regarded as infrequent- their detection is important due to the possibilities for therapy and family genetic counselling. The main symptoms of IEM in the adult are neurological, followed by hepatic. Two basic modes of onset can be established. One is acute, normally taking the form of consciousness alteration, lethargy, coma of unknown etiology in a previously healthy patient (urea cycle deficits, homocysteine remethylation disorders and porphyries are the most frequent causes). The other is an insidious, often progressive, chronic symptomathology that can involve complex clinical features, and more rarely a symptom that is isolated in a persistent way (Wilson's disease, mitochondrial diseases, lysosomal storage disorders, Refsum's disease and glycogenosis are some examples of this group). It is especially important to determine the forms of acute onset as these can present situations of extreme emergency where appropriate conduct can prevent the death of the patient. In this case, simple laboratory examinations, such as determination of ammonia, homocysteine, lactate, acylcarnitines, amino acids, organic and porfirines, can guide the diagnosis and enable the start of intensive treatment. This article provides a practical approach that deals with the general characteristics and the clinical keys for suspecting the most usual IEMs in the adult.

[New insights in inborn errors of metabolism are leading to new paradigms in child neurology]. / Nuevos conocimientos sobre errores congenitos del metabolismo estan dando lugar a nuevos paradigmas en neuropediatria.

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. Different levels of complexity should be integrated in the much-needed novel child neurology paradigm. Classically, the descriptions of neurological diseases have relied on neuroanatomy and neurophysiology. However, metabolism, which strongly orchestrates the regulation of neuronal functions, has been mostly neglected in the study of brain disorders. Paradoxically, inborn errors of metabolism (IEM) have moved in the opposite direction. With more than 1100 IEM, almost 80% of which exhibit neurological symptoms, they have evolved from being initially considered as mere anecdotes to be a fundamental requisite in neuropediatric educational programs. Additionally, new complex molecule defects are leading to integrate classic metabolism and cell biology into the specific compartmentalized structure of the nervous system («cellular neurometabolism¼). This article is a brief summary of the updated IEM classification combined with major neurological presentations in a tentative towards a pathophysiology based clinical practice in child neurology. In particular we emphasize a clinical approach focused in a continuum/spectrum of symptoms.

TITLE: Nuevos conocimientos sobre errores congenitos del metabolismo estan dando lugar a nuevos paradigmas en neuropediatria.En los ultimos anos, la era -omica ya ha transformado la neuropediatria. La secuenciacion de alto rendimiento --next generation sequencing (NGS)-- ha permitido identificar numerosos genes y fenotipos nuevos que provocan enfermedades. Aunque la genetica tiene indudablemente una gran importancia como herramienta diagnostica, no es de tanta utilidad cuando se trata de obtener una comprension mas amplia de los mecanismos involucrados en la disfuncion cerebral. Los neuropediatras corren el riesgo de perderse en la genomica si no asumen la necesidad de un nuevo enfoque en su practica clinica. La gran cantidad de datos que arroja la NGS es simplemente un elemento mas en un complejo rompecabezas. Se deberian integrar distintos niveles de complejidad en el nuevo paradigma de la neuropediatria que tanto se echa en falta. Tradicionalmente, las descripciones de las enfermedades neurologicas se han basado en la neuroanatomia y la neurofisiologia. Sin embargo, el metabolismo, que tiene un papel crucial en la regulacion de las funciones neuronales, se ha obviado en la mayoria de estudios sobre los trastornos cerebrales. Paradojicamente, los errores congenitos del metabolismo (ECM) han tomado la direccion contraria. Con un total de mas de 1.100 ECM, casi el 80% de los cuales manifiestan sintomas neurologicos, han pasado de considerarse inicialmente como anecdoticos a constituir un elemento fundamental en cualquier programa de educacion neuropediatrica. Ademas, los nuevos defectos hallados en las moleculas complejas estan promoviendo la integracion del metabolismo y la biologia celular clasicos en la estructura compartimentada especifica del sistema nervioso («neurometabolismo celular¼). Este articulo constituye un breve resumen de la clasificacion de los ECM actualizada en combinacion con las principales presentaciones neurologicas en un intento de lograr una practica clinica neuropediatrica basada en la fisiopatologia. De manera particular, hacemos hincapie en un enfoque clinico centrado en un amplo continuo/espectro de sintomas.

Secondary alteration of the transferrin isoelectric focusing pattern in a case of bacterial meningitis.

Congenital disorders of glycosylation (CDG) are a group of inherited defects in the synthesis and processing of the linked glycans of glycoproteins and other glycoconjugates. The phenotypic spectrum presents wide variability, and clinical diagnosis is not reliable in most cases. Isoelectric focusing (IEF) of serum transferrin is widely used as a tool to detect CDG. We describe a paediatric patient presenting an altered serum transferrin pattern due to a secondary disorder of glycosylation caused by pneumococcal meningitis (Streptococcus pneumoniae, serotype 19A). During admission, brain CT scan and MRI showed acute ischaemic lesions in brain frontotemporal parenchyma, and enlarged subarachnoidal spaces in the frontal area resembling a chronic injury. This led us to screen for inborn errors of metabolism potentially associated with these findings (homocystinuria, glutaric aciduria, CDG syndromes). Biochemical studies for the screening of these inborn errors of metabolism were normal except for sialotransferrin isoelectric focusing, which showed a type 2 pattern. However, 16 days later, together with the remission of the meningitis process, the sialotransferrin pattern had normalized. The apolipoprotein C-III (an O-glycoprotein) profile was normal in all samples analysed. In conclusion, infectious events should be ruled out in the differential diagnosis of CDG syndromes. Furthermore, our findings highlight the possibility that the type 2 IEF pattern of serum sialotransferrin detected in some patients with neonatal death due to organ failure and septic events might be secondary to the infectious process.

[Multiple familial cerebral cavernomatosis]. / Cavernomatosis múltiple cerebral familiar.

INTRODUCTION: Intracraneal vascular malformations are congenital lesions due to alterations in the development of arteriocapillary network. Cavernomas are present in 0.4% of people, and represent 5-13% of all cerebrovascular malformations. They are multilobulated clearly delimited lesions that contain blood at different evolution. Cavernomas can be single or multiple, and sporadic or familial. Inheritance pattern in familial cases is autosomal dominant and three involved genes have been described. CASE REPORTS: We made a retrospective review of clinical histories of two patients diagnosed of multiple familial cavernomatosis. First patient's onset was with partial seizures. Magnetic resonance (MR) showed a frontal cavernoma probable responsible of seizures, and other lesions in frontal and parietal lobes. Second patient consulted for psychomotor delay and behaviour disorder. MR showed multiple cavernomas. In the first patient, one lesion was surgically removed. In second patient, the attitude was expectant. In both cases familial study was done and multiple cavernomas were found in both parents. CONCLUSIONS: Cavernomas are a type of vascular malformations with specific histological features. Usual clinical characteristics are seizures and parenchymatous bleeding. The appearance of MR has permitted the diagnosis of asymptomatic cavernomas and is currently considered to be the technique of choice for this purpose. In familial cases, multiple lesions are found in 84%, often in association with family history of seizures. Surgical treatment must be considered in patients with symptomatic or progressive lesions that are accessible. All cases must be clinically and MR followed.

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: A case report. / Déficit de 3-hidroxiacil-CoA-deshidrogenasa de cadena larga: a propósito de un caso.

CLINICAL CASE: A five-year-old patient, with a diagnosis of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, was referred for an ophthalmological examination. He had a history of acute metabolic crises precipitated by intercurrent infections,as well as rhabdomyolysis. The fundoscopic examination revealed a peripapillary chorioretinal atrophy and a diffuse granular appearance of the macular retinal pigment epithelium. Best corrected visual acuity was 6/6 in both eyes, and he had a normal electroretinography test. DISCUSSION: We perform a review of the literature and recent findings in relation to this disease through the description of a clinical case in order to improve the knowledge of this uncommon disorder.

Diseases of the Synaptic Vesicle: A Potential New Group of Neurometabolic Disorders Affecting Neurotransmission.

The general concept of inborn error of metabolism is currently evolving into the interface between classical biochemistry and cellular biology. Basic neuroscience is providing increasing knowledge about the mechanisms of neurotransmission and novel related disorders are being described. There is a necessity of updating the classic concept of "inborn error of neurotransmitters (NT)" that considers mainly defects of synthesis and catabolism and transport of low weight NT molecules. Monogenic defects of the synaptic vesicle (SV), and especially those affecting the SV cycle are a potential new group of NT disorders since they end up in abnormal NT turnover and release. The most common clinical manifestations include epilepsy, intellectual disability, autism and movement disorders, and are in the continuum symptoms of synaptopathies. Interestingly, brain malformations and neurodegenerative conditions are also present within SV diseases. Metabolomics, proteomics, and other -omic techniques probably will provide biomarkers and contribute to therapeutic targets in the future.

Dataset reporting BCKDK interference in a BCAA-catabolism restricted environment.

This data article contains complementary figures to the research article "Mitochondrial response to the BCKDK-deficiency: some clues to understand the positive dietary response in this form of autism" [1]. Herein we present data relative to the effect of knocking down BCKDK gene on the real time oxygen consumption rate of fibroblasts obtained from a Maple Syrup Urine Disease (MSUD) patient. Interference of BCKDK expression on such cells showing a reduced branched-chain α-ketoacid dehydrogenase (BCKDHc) activity; let us generate a scenario to study the direct effect of BCKDK absence in an environment of high branched-chain amino acids (BCAAs) concentrations. Data relative to the effectiveness of the knockdown together with the potentiality of the BCKDK-knockdown to increase the deficient branched-chain α-ketoacid dehydrogenase activity detected in MSUD patients are also shown.

A statistical algorithm showing coenzyme Q10 and citrate synthase as biomarkers for mitochondrial respiratory chain enzyme activities.

Laboratory data interpretation for the assessment of complex biological systems remains a great challenge, as occurs in mitochondrial function research studies. The classical biochemical data interpretation of patients versus reference values may be insufficient, and in fact the current classifications of mitochondrial patients are still done on basis of probability criteria. We have developed and applied a mathematic agglomerative algorithm to search for correlations among the different biochemical variables of the mitochondrial respiratory chain in order to identify populations displaying correlation coefficients >0.95. We demonstrated that coenzyme Q10 may be a better biomarker of mitochondrial respiratory chain enzyme activities than the citrate synthase activity. Furthermore, the application of this algorithm may be useful to re-classify mitochondrial patients or to explore associations among other biochemical variables from different biological systems.

Muscle coenzyme Q10 concentrations in patients with probable and definite diagnosis of respiratory chain disorders.

Coenzyme Q(10) (CoQ) deficiency syndrome is a disorder of unknown ethiology that may cause different forms of mitochondrial encephalomyopathy. In the present study our aim was to analyse CoQ concentration and mitochondrial respiratory chain (MRC) enzyme activities in muscle biopsies of patients with clinical suspicion and/or biochemical-molecular diagnosis of a mitochondrial disorder. We studied 36 patients classified into 3 groups: 1) 14 patients without a definitive diagnosis of mitochondrial disease, 2) 13 patients with decreased CI + III and II + III activities of the MRC, and 3) 9 patients with definitive diagnosis of mitochondrial disease. Only 1 of the 14 patients of group 1 showed slightly reduced CoQ values in muscle. Six of the 13 patients from group 2 showed partial CoQ deficiency in muscle and 1 of the 9 cases from group 3 presented a slight CoQ deficiency. Significantly positive correlation was observed between CI + III and CII + III activities with CoQ concentrations in the 36 muscle homogenates from patients (r = 0.555; p = 0.001; and r = 0.460; p = 0.005, respectively). In conclusion, measurement of MRC enzyme activities is a useful tool for the detection of CoQ deficiency, which should be confirmed by CoQ quantification.

[Inborn errors of metabolism with neurological symptomathology in the neonatal period]. / Errores congénitos del metabolismo con manifestaciones neurológicas de presentación neonatal.

INTRODUCTION: Congenital metabolic diseases are considered as rare diseases because of their low incidence and their clinical symptoms at onset. Sometimes they can just begin in the neonatal period. Their progressive knowledge and the availability of specific and sensitive biochemical procedures allow us to diagnose many congenital metabolic diseases, which were not recognized some years ago. PATIENTS AND METHODS: We reviewed the 52 patients with congenital metabolic diseases diagnosed for the last 25 years in our centre, evaluating the clinical presentation, neurological symptoms, complementary exams and clinical evolution. RESULTS: The mean age at onset of symptoms was 5 days and the mean age at diagnosis was 88 days of age. We considered a first group of 36 patients with inborn errors of intermediary metabolism, in whom hypotonia, weight loss and seizures are the main symptoms. The second group was composed of 8 patients with defective energy metabolism, who showed abnormal respiratory rhythm and hypotonia. Finally, we considered 8 patients with diseases of the complex molecules, who presented with hypotonia and cataracts as common symptoms at onset. The more common neurological symptoms in this period were hypotonia (60%), sensorial deficit (35%) and refractory seizures (23%). The complementary laboratory tests in the first phases of the diseases allowed us to suspect a congenital metabolic disease especially among intermediary and energy defects. EEG registration and CSF samples were important to diagnose some inborn errors of intermediary metabolism. In the first steps, the neuroimaging was less orientative, even if it allow the exclusion of other diseases. More than half of the patients with inborn errors of metabolism with onset in the neonatal period died within the first year of life. CONCLUSION: It is really important to suspect these diseases in the neonatal period so as to achieve an early diagnosis and therapy which may reduce the morbimortality.