[Argentinean Consensus on the Diagnosis and Treatment of Niemann- Pick Disease Type C]. / Consenso argentino sobre diagnóstico y tratamiento de la enfermedad de Niemann-Pick Tipo C.

Niemann-Pick type C (NPC) is a disorder of the lysosomal metabolism due to biallelic pathogenic variants in NPC1 or NPC2. Intracellular deposit of lipids, mainly unesterified cholesterol, gives rise to oxidative damage in several tissues, mainly neurons, spleen and liver. This, in turn, is associated with a myriad of neurological / psychiatric and visceral symptoms, with wide variability in age of presentation, from prenatal / neonatal to adult-onset forms of the disease. The last few years have seen considerable progress in understanding this disease and its management. In this consensus, current approaches to the diagnosis, follow-up and treatment of NPC (including the use of miglustat, the only specific drug approved at the time) are discussed by an Argentinian panel of experts.

La enfermedad de Niemann-Pick tipo C (NPC) es un trastorno del metabolismo lisosomal que se debe a la presencia de variantes patogénicas bialélicas en los genes NPC1 o NPC2. El depósito intracelular de lípidos, especialmente colesterol no esterificado, provoca daño oxidativo en diversos tejidos, especialmente neuronas, bazo e hígado. Esto, a su vez, induce la aparición de un conjunto de síntomas neurológicos / psiquiátricos y viscerales, con una amplia variabilidad de edad de aparición, desde formas prenatales / neonatales hasta otras de aparición en la vida adulta. En los últimos años ha habido avances considerables en la comprensión sobre esta enfermedad y su manejo. En el presente consenso un grupo de expertos argentinos abordan los enfoques actuales de diagnóstico, seguimiento y tratamiento de NPC, incluyendo el uso de miglustat como única terapia específica aprobada en la actualidad.

Consenso Argentino sobre Diagnóstico y Tratamiento de la Enfermedad de Niemann-Pick tipo C / Argentinean Consensus on the Diagnosis and Treatment of Niemann-Pick Disease type C

Resumen La enfermedad de Niemann-Pick tipo C (NPC) es un trastorno del metabolismo lisosomal que se debe a la presencia de variantes patogénicas bialélicas en los genes NPC1 o NPC2. El depósito intracelular de lípidos, especialmente colesterol no esterificado, provoca daño oxidativo en diversos tejidos, especialmente neuronas, bazo e hígado. Esto, a su vez, induce la aparición de un conjunto de síntomas neurológicos/psiquiátricos y viscerales, con una amplia variabilidad de edad de apa rición, desde formas prenatales/neonatales hasta otras de aparición en la vida adulta. En los últimos años ha habido avances considerables en la comprensión sobre esta enfermedad y su manejo. En el presente consenso un grupo de expertos argentinos abordan los enfoques actuales de diagnóstico, seguimiento y tratamiento de NPC, incluyendo el uso de miglustat como única terapia específica aprobada en la actualidad.

Abstract Niemann-Pick type C (NPC) is a disorder of the lyso somal metabolism due to biallelic pathogenic variants in NPC1 or NPC2. Intracellular deposit of lipids, mainly unesterified cholesterol, gives rise to oxidative damage in several tissues, mainly neurons, spleen and liver. This, in turn, is associated with a myriad of neurologi cal/psychiatric and visceral symptoms, with wide vari ability in age of presentation, from prenatal/neonatal to adult-onset forms of the disease. The last few years have seen considerable progress in understanding this disease and its management. In this consensus, current approaches to the diagnosis, follow-up and treatment of NPC (including the use of miglustat, the only specific drug approved at the time) are discussed by an Argentin ian panel of experts.

Clinical, neuroradiological, and molecular characterization of mitochondrial threonyl-tRNA-synthetase (TARS2)-related disorder.

PURPOSE: Biallelic variants in TARS2, encoding the mitochondrial threonyl-tRNA-synthetase, have been reported in a small group of individuals displaying a neurodevelopmental phenotype but with limited neuroradiological data and insufficient evidence for causality of the variants. METHODS: Exome or genome sequencing was carried out in 15 families. Clinical and neuroradiological evaluation was performed for all affected individuals, including review of 10 previously reported individuals. The pathogenicity of TARS2 variants was evaluated using in vitro assays and a zebrafish model. RESULTS: We report 18 new individuals harboring biallelic TARS2 variants. Phenotypically, these individuals show developmental delay/intellectual disability, regression, cerebellar and cerebral atrophy, basal ganglia signal alterations, hypotonia, cerebellar signs, and increased blood lactate. In vitro studies showed that variants within the TARS2301-381 region had decreased binding to Rag GTPases, likely impairing mTORC1 activity. The zebrafish model recapitulated key features of the human phenotype and unraveled dysregulation of downstream targets of mTORC1 signaling. Functional testing of the variants confirmed the pathogenicity in a zebrafish model. CONCLUSION: We define the clinico-radiological spectrum of TARS2-related mitochondrial disease, unveil the likely involvement of the mTORC1 signaling pathway as a distinct molecular mechanism, and establish a TARS2 zebrafish model as an important tool to study variant pathogenicity.

CDKL5-associated developmental and epileptic encephalopathy: A long-term, longitudinal electroclinical study of 22 cases.

OBJECTIVE: The study was conducted to analyze the possible diagnostic value of the electroclinical semiology of the epileptic seizures. METHODS: We evaluated the medical records of 17 females and 5 males with CDKL5 deficiency disorder (CDD) considering the long-term evolution, including the polygraphic video-EEG recordings. RESULTS: We recognized three disease phases. We found that the seizure semiology was already recognizable in the first phase of the syndrome. In the short-term evolution, all patients had focal motor and 12/21 hypermotor seizures. Both epileptic spasms and myoclonic seizures were already present in more than half of the cases in the first 2 months after onset. In the second phase, the intermediate period, the polymorphic pattern was maintained, but in eight patients the electroclinical pattern of epileptic encephalopathy with hypsarrhythmia appeared. In the long-term period, the seizure polymorphism continued but myoclonic and epileptic spasms diminished. Tonic seizures appeared in the last 2 phases. Progressively, with the aggravation of seizures and paroxysmal EEG abnormalities impairment of the neurocognitive status was observed. Severe behavioral disturbances were seen in eight and autistic-like features in 14. CONCLUSION: CDD is a true developmental and epileptic encephalopathy with a specific etiology characterized by the early appearance of epileptic seizures that quickly become polymorphic and drug resistant in infants that are most often female and already have neurological impairment. Polygraphic video-EEG recordings are important to recognize ictal events of the association of hypermotor seizures, epileptic spasms in clusters, and massive myoclonic jerks, already present at onset.

Deficiencia del transportador de glucosa tipo 1: aspectos clínicos, diagnóstico y terapéutica / Glucose transporter type 1 deficiency syndrome: clinical aspects, diagnosis, and treatment

El síndrome de deficiencia del transportador de glucosa tipo 1 es una enfermedad de causa genética, que involucra el gen SLC2A1. En general, se presenta durante los primeros años de vida con retraso en la adquisición de pautas madurativas, epilepsia farmacorresistente y desórdenes del movimiento. La clínica y la disminución de glucosa en líquido cefalorraquídeo permiten sospechar el diagnóstico, el cual debe ser confirmado mediante el estudio molecular del gen SLC2A1. Debido a que se trata de una enfermedad poco frecuente y de expresión clínica variable, el diagnóstico precoz suele representar un desafío para los equipos de salud. Este es importante, ya que la implementación de la terapia cetogénica logra controlar las manifestaciones clínicas y mejora el pronóstico a largo plazo. Presentamos una revisión sobre el déficit del transportador de glucosa tipo 1, que abarca sus características clínicas, bioquímicas, moleculares y terapéuticas.

Glucose transporter type 1 deficiency with a typical onset is a genetic disorder associated with the SLC2A1 gene. Usually appears during the first years of life with severe developmental delay, drugresistant epilepsy, and movement disorders. Diagnosis is suspected based on clinical manifestations and a low glucose level in cerebrospinal fluid, and should be confirmed by the molecular genetic study of the SLC2A1 gene. As it is a rare disease with variable clinical expression, early diagnosis is often challenging for the healthcare team. Nevertheless, this is important because early implementation of ketogenic therapy will lead to control of the clinical manifestations and a better long-term prognosis. Here we review the glucose transporter type 1 deficiency syndrome focusing on its clinical, biochemical, molecular, and therapeutic characteristics.

Glucose transporter type 1 deficiency syndrome: clinical aspects, diagnosis, and treatment. / Deficiencia del transportador de glucosa tipo 1: aspectos clínicos, diagnóstico y terapéutica.

Glucose transporter type 1 deficiency with a typical onset is a genetic disorder associated with the SLC2A1 gene. Usually appears during the first years of life with severe developmental delay, drugresistant epilepsy, and movement disorders. Diagnosis is suspected based on clinical manifestations and a low glucose level in cerebrospinal fluid,and should be confirmed by the molecular genetic study of the SLC2A1 gene. As it is a rare disease with variable clinical expression, early diagnosis is often challenging for the healthcare team. Nevertheless, this is important because early implementation of ketogenic therapy will lead to control of the clinical manifestations and a better long-term prognosis. Here we review the glucose transporter type 1 deficiency syndrome focusing on its clinical, biochemical, molecular, and therapeutic characteristics.

El síndrome de deficiencia del transportador de glucosa tipo 1 es una enfermedad de causa genética, que involucra el gen SLC2A1. En general, se presenta durante los primeros años de vida con retraso en la adquisición de pautas madurativas, epilepsia farmacorresistente y desórdenes del movimiento. La clínica y la disminución de glucosa en líquido cefalorraquídeo permiten sospechar el diagnóstico, el cual debe ser confirmado mediante el estudio molecular del gen SLC2A1. Debido a que se trata de una enfermedad poco frecuente y de expresión clínica variable, el diagnóstico precoz suele representar un desafío para los equipos de salud. Este es importante, ya que la implementación de la terapia cetogénica logra controlar las manifestaciones clínicas y mejora el pronóstico a largo plazo. Presentamos una revisión sobre el déficit del transportador de glucosa tipo 1, que abarca sus características clínicas, bioquímicas, moleculares y terapéuticas.

Clinical and genetic study of developmental and epileptic encephalopathy in Argentinean pediatric patients.

INTRODUCTION: The aim of this study was to extend our knowledge of the genetic background of Argentinean pediatric patients with developmental and epileptic encephalopathy (DEE) applying a next generation sequencing (NGS) panel. METHODS: Thirty one patients with DEE were studied, including these phenotypes: Dravet syndrome (n:7), Dravet like syndrome (n:3), West syndrome (WS) (n:6), WS that evolved to Lennox-Gastaut syndrome (LGS) (n:4), epilepsy of infancy with migrating focal seizures (n:2), continuous spikes and waves during slow sleep evolving to LGS (n:1), LGS (n:1), myoclonic status in non-progressive encephalopathy (n:1), myoclonic atonic epilepsy (n:1), epileptic encephalopathy with multifocal spikes (n:1) and unclassified epileptic encephalopathy (n:4). Fifty-two genes frequently associated with DEE were studied by NGS in genomic DNA from peripheral blood. RESULTS: Relevant variants were detected in 12 cases; 6 novel pathogenic or likely pathogenic variants, 6 previously reported as pathogenic and 1 variant of unknown significance. Single-nucleotide heterozygous variants were identified in the SCN1A (5), GABRG2 (1), STXBP1 (2) genes, a mosaic variant in SCN2A (1) and a homozygous variant in SCN1B (1). Additionally, a heterozygous deletion involving the SCN1A, SCN2A and SCN3A genes (1), and the most frequent triplet repeat expansion in the ARX gene (1) were detected. DISCUSSION: Genetic diagnosis was made in 39% of patients. We emphasize the importance of considering mosaic variants, copy number variants and hereditary forms when designing and interpreting molecular studies, to optimize diagnosis and management of patients. Approximately 42% of the detected variants were novel, expanding the knowledge of the molecular basis of DEEs in Latin-American patients.

Introducción: El objetivo del estudio fue ampliar el conocimiento de las bases moleculares de las encefalopatías epilépticas y del desarrollo (EED) en pacientes pediátricos argentinos aplicando un panel de secuenciación de nueva generación (NGS). Métodos: Se analizaron 31 pacientes con los fenotipos clínicos de síndrome de Dravet (n:7), síndrome símil Dravet (n:3), síndrome de West (SW) (n:6), SW que evoluciona a síndrome de Lennox Gastaut (SLG)(N:4), epilepsia de la infancia con crisis focales migratorias (n:2), actividad de punta onda continua durante el sueño que evolucionan a SLG (n:1), SLG (n:1), encefalopatía no progresiva con estatus mioclónico (n:1), epilepsia mioclónica atónica (n:1), encefalopatía epiléptica con espigas multifocales (n:1) y encefalopatía epiléptica indeterminada (n:4). Se estudiaron los 52 genes más frecuentemente asociados a EED a través de NGS, en ADN extraído de sangre periférica. Resultados: Se identificaron variantes relevantes en 12 casos, de las cuales 5 fueron nuevas y 6 previamente reportadas como patogénicas o posiblemente patogénicas, mientras que una variante fue clasificada como de significado incierto. Variantes heterocigotas, de nucleótido único, se identificaron en los genes SCN1A (5), GABRG2 (1), STXBP1 (2), una variante en mosaico en SCN2A (1) y otra homocigota en SCN1B (1). Además, se detectó una deleción que involucra a los genes SCN1A, SCN2A y SCN3A (1) y la expansión de repeticiones de tripletes más frecuente en el gen ARX (1). Discusión: Se alcanzó el diagnóstico molecular en el 39% de los pacientes. Remarcamos la importancia de considerar variantes en mosaico, variantes en el número de copias y formas heredadas al momento de diseñar e interpretar los estudios moleculares, de tal forma de optimizar el diagnóstico y seguimiento de los pacientes con EED. Cabe destacar, que el 42% de las variantes detectadas fueron nuevas, ampliando nuestro conocimiento sobre las bases moleculares de las EED en población latino americana.

Clinical and genetic study of developmental and epileptic encephalopathy in argentinean pediatric patients / Estudio clínico y genético de encefalopatía epiléptica y del desarrollo en pacientes pediátricos argentinos

Abstract Introduction: The aim of this study was to extend our knowledge of the genetic background of Argentinean pediatric patients with developmental and epileptic encephalopathy (DEE) applying a next generation sequencing (NGS) panel. Methods: Thirty one patients with DEE were studied, including these phenotypes: Dravet syndrome (n:7), Dravet like syndrome (n:3), West syndrome (WS) (n:6), WS that evolved to Lennox-Gastaut syndrome (LGS) (n:4), epilepsy of infancy with migrating focal seizures (n:2), continuous spikes and waves during slow sleep evolving to LGS (n:1), LGS (n:1), myoclonic status in non-progressive encephalopathy (n:1), myoclonic atonic epilepsy (n:1), epileptic encephalopathy with multifocal spikes (n:1) and unclassified epileptic encephalopathy (n:4). Fifty-two genes frequently associated with DEE were studied by NGS in genomic DNA from peripheral blood. Results: Relevant variants were detected in 12 cases; 6 novel pathogenic or likely pathogenic variants, 6 previously reported as pathogenic and 1 variant of unknown sig nificance. Single-nucleotide heterozygous variants were identified in the SCN1A (5), GABRG2 (1), STXBP1 (2) genes, a mosaic variant in SCN2A (1) and a homozygous variant in SCN1B (1). Additionally, a heterozygous deletion involving the SCN1A, SCN2A and SCN3A genes (1), and the most frequent triplet repeat expansion in the ARX gene (1) were detected. Discussion: Genetic diagnosis was made in 39% of patients. We emphasize the importance of considering mosaic variants, copy number variants and hereditary forms when designing and interpreting molecular studies, to optimize diagnosis and management of patients. Approximately 42% of the de tected variants were novel, expanding the knowledge of the molecular basis of DEEs in Latin-American patients.

Resumen Introducción: El objetivo del estudio fue ampliar el conocimiento de las bases moleculares de las encefalopatías epilépticas y del desarrollo (EED) en pacientes pediátricos argentinos aplicando un panel de secuenciación de nueva generación (NGS). Métodos: Se analizaron 31 pacientes con los fenotipos clínicos de síndrome de Dra vet (n:7), síndrome símil Dravet (n:3), síndrome de West (SW) (n:6), SW que evoluciona a síndrome de Lennox Gastaut (SLG)(N:4), epilepsia de la infancia con crisis focales migratorias (n:2), actividad de punta onda continua durante el sueño que evolucionan a SLG (n:1), SLG (n:1), encefalopatía no progresiva con estatus mioclónico (n:1), epilepsia mioclónica atónica (n:1), encefalopatía epiléptica con espigas multifocales (n:1) y encefalopatía epiléptica indeterminada (n:4). Se estudiaron los 52 genes más frecuentemente asociados a EED a través de NGS, en ADN extraído de sangre periférica. Resultados: Se identificaron variantes relevantes en 12 casos, de las cuales 5 fueron nuevas y 6 previamente reportadas como patogénicas o posiblemente patogénicas, mien tras que una variante fue clasificada como de significado incierto. Variantes heterocigotas, de nucleótido único, se identificaron en los genes SCN1A (5), GABRG2 (1), STXBP1 (2), una variante en mosaico en SCN2A (1) y otra homocigota en SCN1B (1). Además, se detectó una deleción que involucra a los genes SCN1A, SCN2A y SCN3A (1) y la expansión de repeticiones de tripletes más frecuente en el gen ARX (1). Discusión: Se alcanzó el diagnóstico molecular en el 39% de los pacientes. Remarcamos la importancia de considerar variantes en mosaico, variantes en el número de copias y formas heredadas al momento de diseñar e interpretar los estudios moleculares, de tal forma de optimizar el diagnóstico y seguimiento de los pacientes con EED. Cabe destacar, que el 42% de las variantes detectadas fueron nuevas, ampliando nuestro conocimiento sobre las bases mole culares de las EED en población latino americana.

Clinical and molecular characterization of mitochondrial DNA disorders in a group of Argentinian pediatric patients.

OBJECTIVE: To describe the clinical and molecular features of a group of Argentinian pediatric patients with mitochondrial DNA (mtDNA) disorders, and to evaluate the results of the implementation of a classical approach for the molecular diagnosis of mitochondrial diseases. METHODS: Clinical data from 27 patients with confirmed mtDNA pathogenic variants were obtained from a database of 89 patients with suspected mitochondrial disease, registered from 2014 to 2020. Clinical data, biochemical analysis, neuroimaging findings, muscle biopsy and molecular studies were analyzed. RESULTS: Patients were 18 females and 9 males, with ages at onset ranging from 1 week to 14 years (median = 4 years). The clinical phenotypes were: mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome (n = 11), Leigh syndrome (n = 5), Kearns-Sayre syndrome (n = 3), Chronic Progressive External Ophthalmoplegia (n = 2), Leber hereditary optic neuropathy (n = 2), myoclonic epilepsy associated with ragged-red fibers (n = 1) and reversible infantile myopathy with cytochrome-C oxidase deficiency (n = 3). Most of the patients harbored pathogenic single nucleotide variants, mainly involving mt-tRNA genes, such as MT-TL1, MT-TE and MT-TK. Other point variants were found in complex I subunits, like MT-ND6, MT-ND4, MT-ND5; or in MT-ATP6. The m.13513G > A variant in MT-ND5 and the m.9185 T > C variant in MT-ATP6 were apparently de novo. The rest of the patients presented large scale-rearrangements, either the "common" deletion or a larger deletion. CONCLUSIONS: This study highlights the clinical and genetic heterogeneity of pediatric mtDNA disorders. All the cases presented with classical phenotypes, being MELAS the most frequent. Applying classical molecular methods, it was possible to achieve a genetic diagnosis in 30% of the cases, suggesting that this is an effective first approach, especially for those centers from low-middle income countries, leaving NGS studies for those patients with inconclusive results.

Molecular diagnosis of epileptic encephalopathy of the first year of life applying a customized gene panel in a group of Argentinean patients.

OBJECTIVE: The aim of this study was to perform a molecular characterization of 17 Argentinean pediatric patients with diagnosis of having epileptic encephalopathies (EEs) of the first year of life without known etiology, applying next-generation sequencing (NGS). METHODS: We included 17 patients with EE with age of onset under 12 months without known etiology after ruling out structural abnormalities, metabolic disorders, and large chromosomal abnormalities. They presented with the following clinical phenotypes: Dravet syndrome (DS; n: 7), epilepsy of infancy with migrating focal seizures (EIMFS; n: 3), West syndrome (WS; n: 2), and undetermined epileptic encephalopathy (UEE; n: 5). Neurologic examinations, seizure semiology, brain magnetic resonance imaging, and standard electroencephalography (EEG) or video-EEG studies were performed in all cases. Using a custom amplicon strategy, we designed an NGS panel to study 47 genes associated with EEs. RESULTS: Pathogenic variants were detected in 8 cases (47%), including seven novel pathogenic variants and one previously reported as being pathogenic. The pathogenic variants were identified in 6 patients with DS (SCN1A gene), one with EIMFS (SCN2A gene), and one with UEE (SLC2A1 gene). Nonrelevant variants were identified in the patients with WS. CONCLUSION: We demonstrated the feasibility of an NGS-gene panel approach for the analysis of patients with EE in our setting. A genetic diagnosis was achieved in nearly 50% of patients, 87% of them presenting with nonpreviously reported variants. The early identification of the underlying causative genetic alteration will be a valuable tool for providing prognostic information and genetic counselling and also to improve therapeutic decisions in Argentinean patients.

Mitochondrial stress triggers a pro-survival response through epigenetic modifications of nuclear DNA.

Mitochondrial dysfunction represents an important cellular stressor and when intense and persistent cells must unleash an adaptive response to prevent their extinction. Furthermore, mitochondria can induce nuclear transcriptional changes and DNA methylation can modulate cellular responses to stress. We hypothesized that mitochondrial dysfunction could trigger an epigenetically mediated adaptive response through a distinct DNA methylation patterning. We studied cellular stress responses (i.e., apoptosis and autophagy) in mitochondrial dysfunction models. In addition, we explored nuclear DNA methylation in response to this stressor and its relevance in cell survival. Experiments in cultured human myoblasts revealed that intense mitochondrial dysfunction triggered a methylation-dependent pro-survival response. Assays done on mitochondrial disease patient tissues showed increased autophagy and enhanced DNA methylation of tumor suppressor genes and pathways involved in cell survival regulation. In conclusion, mitochondrial dysfunction leads to a "pro-survival" adaptive state that seems to be triggered by the differential methylation of nuclear genes.

Late-onset childhood neuronal ceroid lipofuscinosis: Early clinical and electroencephalographic markers.

PURPOSE: The objective of the study was to describe the initial clinical and electroencephalographic findings in children with late-infantile neuronal ceroid lipofuscinosis (LINCL). METHOD: The clinical charts of 35 patients seen between 1990 and 2016 were reviewed. The patients were divided into two groups: Group 1 (G1) consisting of 12 patients with NCL type 2 (CLN2) disease confirmed by enzymatic activity in dried blood spots on filter paper and/or genetic studies, and Group 2 (G2) consisting of 23 patients with a diagnosis of LINCL based on pathology studies by muscle biopsy. RESULTS: Mean age at symptom onset was 3 years in G1 and 3.4 years in G2. Symptoms at onset were epilepsy in 58%, language delay in 34%, and gait disturbances in 8% of patients in G1 and epilepsy in 52.1%, language delay in 26%, gait disturbances in 17.4%, and loss of visual acuity in 4.5% in G2. The most common seizure types in G1 patients were myoclonic in 3/7, generalized tonic-clonic in 2/7, focal motor in 1/7, and febrile seizures in 1/7; in G2 patients they were myoclonic in 5/12, generalized tonic-clonic in 3/12, myoclonic-atonic in 2/12, and febrile seizures in 2/12. A photoparoxysmal response to intermittent photic stimulation (IPS) was found in the initial EEG in 9/12 patients in G1 (mean age 3.8 years) and in 10/13 patients in G2 (mean age 3.9 years). CONCLUSIONS: There were no significant differences between both groups. Seizures, especially myoclonic, are the most common symptom at onset followed by language delay and gait disturbances. Low-frequency IPS is a useful study that may help facilitate the diagnosis of the disease.

Retrospective natural history of thymidine kinase 2 deficiency.

BACKGROUND: Thymine kinase 2 (TK2) is a mitochondrial matrix protein encoded in nuclear DNA and phosphorylates the pyrimidine nucleosides: thymidine and deoxycytidine. Autosomal recessive TK2 mutations cause a spectrum of disease from infantile onset to adult onset manifesting primarily as myopathy. OBJECTIVE: To perform a retrospective natural history study of a large cohort of patients with TK2 deficiency. METHODS: The study was conducted by 42 investigators across 31 academic medical centres. RESULTS: We identified 92 patients with genetically confirmed diagnoses of TK2 deficiency: 67 from literature review and 25 unreported cases. Based on clinical and molecular genetics findings, we recognised three phenotypes with divergent survival: (1) infantile-onset myopathy (42.4%) with severe mitochondrial DNA (mtDNA) depletion, frequent neurological involvement and rapid progression to early mortality (median post-onset survival (POS) 1.00, CI 0.58 to 2.33 years); (2) childhood-onset myopathy (40.2%) with mtDNA depletion, moderate-to-severe progression of generalised weakness and median POS at least 13 years; and (3) late-onset myopathy (17.4%) with mild limb weakness at onset and slow progression to respiratory insufficiency with median POS of 23 years. Ophthalmoparesis and facial weakness are frequent in adults. Muscle biopsies show multiple mtDNA deletions often with mtDNA depletion. CONCLUSIONS: In TK2 deficiency, age at onset, rate of weakness progression and POS are important variables that define three clinical subtypes. Nervous system involvement often complicates the clinical course of the infantile-onset form while extraocular muscle and facial involvement are characteristic of the late-onset form. Our observations provide essential information for planning future clinical trials in this disorder.

Mitochondrial DNA deletions detected by Multiplex Ligation-dependent Probe Amplification.

The genetic diagnosis algorithm for mitochondrial (mt) diseases starts looking for deletions and common mutations in mtDNA. MtDNA's special features, such as large and variable genome copies, heteroplasmy, polymorphisms, and its duplication in the nuclear genome as pseudogenes (NUMTs), make it vulnerable to diagnostic misleading interpretations. Multiplex Ligation-dependent Probe Amplification (MLPA) is used to detect copy number variations in nuclear genes and its application on mtDNA has not been widely spread. We report three Kearns Sayre Syndrome patients and one Chronic Progressive External Ophthalmoplegia adult, whose diagnostic mtDNA deletions were detected by MLPA using a very low amount of DNA. This managed to "dilute" the NUMT interference as well as enhance MLPA's efficiency. By this report, we conclude that when MLPA is performed upon a reduced amount of DNA, it can detect effectively mtDNA deletions. We propose MLPA as a possible first step method in the diagnosis of mt diseases.

[Acute encephalitis anti-ionotropic glutamate receptor activated N-methyl-D-aspartate (NMDAR): analysis of eleven pediatric cases in Argentina (Benito Yelín Award)]. / Encefalitis aguda mediada por anticuerpos contra el receptor ionotrópico de glutamato activado por N-metil-D-aspartato (NMDAR): análisis de once casos pediátricos en Argentina (Premio Benito Yelín).

Encephalitis are an inflammatory processes of various origin, among which include autoimmune origin. The identification of antibodies against the N-methyl-D- aspartate, allowed clinical immunological characterization of an entity susceptible to immunomodulatory therapy. Originally described in young women associated with ovarian teratoma, is now a recognized entity in children even in the absence of detectable tumors. The aim of the study was conducted through review of medical records, was to describe the clinical, developmental and findings in further studies of eleven children with confirmed diagnosis of this entity through identification of specific antibodies. All debuted with psychiatric symptoms in nine associating seizures, and two extrapyramidal movements. In the evolution of language all had commitment nine severe autonomic symptoms, one with hypoventilation and requirements of ARM. Brain MRI was abnormal in three. Eight had voltage EEG asymmetry and / or amplitude, three of them had spikes. Six had CSF pleocytosis and three of seven positive oligoclonal bands. Five IgM serology for mycoplasma were positive. CPK increase occurred in conjunction with antisychotics in five. With immunomodulatory treatment, five had complete recovery three behavioral disorders / cognitive deficits and one severe. A patient's clinical picture resolved without treatment. In any associated tumor was detected. We conclude that in front of a child with acute encephalopathy and clinical support this entity after infectious cause were ruled out, immunomodulatory therapy should be started early, avoid the use of antipsychotic drugs and search for possible hidden tumors.

Encefalitis aguda mediada por anticuerpos contra el receptor ionotrópico de glutamato activado por N-metil-D-aspartato (NMDAR): análisis de once casos pediátricos en Argentina (Premio Benito Yelín) / [Acute encephalitis anti-ionotropic glutamate receptor activated N-methyl-D-aspartate (NMDAR): analysis of eleven pediatric cases in Argentina (Benito Yelín Award)].

Encephalitis are an inflammatory processes of various origin, among which include autoimmune origin. The identification of antibodies against the N-methyl-D- aspartate, allowed clinical immunological characterization of an entity susceptible to immunomodulatory therapy. Originally described in young women associated with ovarian teratoma, is now a recognized entity in children even in the absence of detectable tumors. The aim of the study was conducted through review of medical records, was to describe the clinical, developmental and findings in further studies of eleven children with confirmed diagnosis of this entity through identification of specific antibodies. All debuted with psychiatric symptoms in nine associating seizures, and two extrapyramidal movements. In the evolution of language all had commitment nine severe autonomic symptoms, one with hypoventilation and requirements of ARM. Brain MRI was abnormal in three. Eight had voltage EEG asymmetry and / or amplitude, three of them had spikes. Six had CSF pleocytosis and three of seven positive oligoclonal bands. Five IgM serology for mycoplasma were positive. CPK increase occurred in conjunction with antisychotics in five. With immunomodulatory treatment, five had complete recovery three behavioral disorders / cognitive deficits and one severe. A patient’s clinical picture resolved without treatment. In any associated tumor was detected. We conclude that in front of a child with acute encephalopathy and clinical support this entity after infectious cause were ruled out, immunomodulatory therapy should be started early, avoid the use of antipsychotic drugs and search for possible hidden tumors.