Broadening the clinical spectrum: molecular mechanisms and new phenotypes of ANO3-dystonia.

Anoctamin 3 (ANO3) belongs to a family of transmembrane proteins that form phospholipid scramblases and ion channels. A large number of ANO3 variants were identified as the cause of craniocervical dystonia, but the underlying pathogenic mechanisms remain obscure. It was suggested that ANO3 variants may dysregulate intracellular Ca2+ signalling, as variants in other Ca2+ regulating proteins like hippocalcin were also identified as a cause of dystonia. In this study, we conducted a comprehensive evaluation of the clinical, radiological, and molecular characteristics of four individuals from four families who carried heterozygous variants in ANO3. The median age at follow-up was 6.6 years (ranging from 3.8 to 8.7 years). Three individuals presented with hypotonia and motor developmental delay. Two patients exhibited generalized progressive dystonia, while one patient presented with paroxysmal dystonia. Additionally, another patient exhibited early dyskinetic encephalopathy. One patient underwent bipallidal deep brain stimulation (DBS) and showed a mild but noteworthy response, while another patient is currently being considered for DBS treatment. Neuroimaging analysis of brain MRI studies did not reveal any specific abnormalities. The molecular spectrum included two novel ANO3 variants (V561L and S116L) and two previously reported ANO3 variants (A599D and S651N). As anoctamins are suggested to affect intracellular Ca2+ signals, we compared Ca2+ signalling and activation of ion channels in cells expressing wild type ANO3 and cells expressing ANO variants. Novel V561L and S116L variants were compared with previously reported A599D and S651N variants and with wtANO3 expressed in fibroblasts isolated from patients or when overexpressed in HEK293 cells. We identified ANO3 as a Ca2+-activated phospholipid scramblase that also conducts ions. Impaired Ca2+ signalling and compromised activation of Ca2+ dependent K+ channels were detected in cells expressing ANO3 variants. In the brain striatal cells of affected patients, impaired activation of KCa3.1 channels due to compromised Ca2+ signals may lead to depolarized membrane voltage and neuronal hyperexcitability and may also lead to reduced cellular viability, as shown in the present study. In conclusion, our study reveals the association between ANO3 variants and paroxysmal dystonia, representing the first reported link between these variants and this specific dystonic phenotype. We demonstrate that ANO3 functions as a Ca2+-activated phospholipid scramblase and ion channel; cells expressing ANO3 variants exhibit impaired Ca2+ signalling and compromised activation of Ca2+-dependent K+ channels. These findings provide a mechanism for the observed clinical manifestations and highlight the importance of ANO3 for neuronal excitability and cellular viability.

Crisis neonatales y evolución a epilepsia en un hospital de tercer nivel / Neonatal seizures and progression to epilepsy in a tertiary hospital

Introducción Las convulsiones neonatales son un reto diagnóstico, dada la inmadurez del recién nacido. La mayoría son secundarias a un evento agudo. Un pequeño porcentaje constituye el inicio de una epilepsia. Objetivos Analizar a los neonatos ingresados en un hospital de tercer nivel con diagnóstico de crisis entre noviembre de 2009 y mayo de 2021, y su evolución posterior a epilepsia. Material y métodos. Se ha realizado un estudio observacional retrospectivo utilizando la base de datos del hospital. Se ha recogido la información de los neonatos con diagnóstico en el alta de ‘convulsiones’ o ‘encefalopatía hipóxico-isquémica moderada o grave’. Se analizaron distintas variables: etiología de las crisis, tipo, persistencia temporal, tratamiento y correlato electroclínico. Resultados De 165 pacientes, 55 presentaron crisis neonatales. En cuanto a la etiología, 43 pacientes (78%) tuvieron crisis secundarias a un evento agudo, de las cuales 19 (34%) fueron encefalopatías hipóxico-isquémicas, y 22 (40%), otras alteraciones agudas. En seis (11%) se encontró alteración genética. Trece pacientes (24%) evolucionaron a una epilepsia posterior, de los cuales siete presentaron una epilepsia sintomática, con un período de latencia tras el evento agudo en dos pacientes. Seis pacientes tuvieron epilepsia neonatal con crisis no provocadas. Veintidós (62%) mostraron correlato electroclínico. El 100% de las crisis confirmadas fueron focales. Todas las crisis se trataron. El fármaco de elección fue el fenobarbital. Conclusiones El diagnóstico de convulsiones neonatales requiere una alta sospecha clínica y una confirmación electroclínica. La mayoría tiene evolución favorable, pero un porcentaje constituye el inicio de una epilepsia, cuya identificación determinará su manejo terapéutico. (AU)

INTRODUCTION Given the immaturity of the newborn, neonatal seizures are a diagnostic challenge. Most of them are secondary to an acute event. A small percentage constitute the onset of epilepsy. AIMS. The aim was to analyse neonates with a diagnosis of seizures admitted to a tertiary hospital between November 2009 and May 2021, and their subsequent progression to epilepsy. Material and methods. A retrospective observational study was carried out using the hospital database. Information was collected on neonates with a discharge diagnosis of ‘seizures’ or ‘moderate or severe hypoxic-ischaemic encephalopathy’. Different variables were analysed: aetiology of the seizures, type, persistence over time, treatment and electroclinical correlates. RESULTS Of 165 patients, 55 presented neonatal seizures. As regards aetiology, 43 patients (78%) had seizures secondary to an acute event, of which 19 (34%) were hypoxic-ischaemic encephalopathies, and 22 (40%) had other acute disorders. Genetic alteration was found in six of them (11%). Thirteen patients (24%) progressed to subsequent epilepsy, of whom seven had symptomatic epilepsy, with a period of latency after the acute event in two patients. Six patients had neonatal epilepsy with unprovoked seizures. Twenty-two (62%) showed electroclinical correlates. All of the confirmed crises (100%) were focal. All the seizures were treated. The drug of choice was phenobarbital. CONCLUSIONS Diagnosis of neonatal seizures requires high clinical suspicion and electroclinical confirmation. Most of them progress favourably, but a percentage constitute the onset of epilepsy, the identification of which will determine their therapeutic management. (AU)

Expanding the phenotypic spectrum of TRAPPC11-related muscular dystrophy: 25 Roma individuals carrying a founder variant.

BACKGROUND: Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetically determined muscle disorders. TRAPPC11-related LGMD is an autosomal-recessive condition characterised by muscle weakness and intellectual disability. METHODS: A clinical and histopathological characterisation of 25 Roma individuals with LGMD R18 caused by the homozygous TRAPPC11 c.1287+5G>A variant is reported. Functional effects of the variant on mitochondrial function were investigated. RESULTS: The c.1287+5G>A variant leads to a phenotype characterised by early onset muscle weakness, movement disorder, intellectual disability and elevated serum creatine kinase, which is similar to other series. As novel clinical findings, we found that microcephaly is almost universal and that infections in the first years of life seem to act as triggers for a psychomotor regression and onset of seizures in several individuals with TRAPPC11 variants, who showed pseudometabolic crises triggered by infections. Our functional studies expanded the role of TRAPPC11 deficiency in mitochondrial function, as a decreased mitochondrial ATP production capacity and alterations in the mitochondrial network architecture were detected. CONCLUSION: We provide a comprehensive phenotypic characterisation of the pathogenic variant TRAPPC11 c.1287+5G>A, which is founder in the Roma population. Our observations indicate that some typical features of golgipathies, such as microcephaly and clinical decompensation associated with infections, are prevalent in individuals with LGMD R18.

PLA2G6-associated neurodegeneration: New insights into brain abnormalities and disease progression.

INTRODUCTION: PLA2G6-associated neurodegeneration (PLAN) comprises a continuum of three phenotypes with overlapping clinical and radiologic features. METHODS: Observational clinical study in a cohort of infantile and childhood onset PLAN patients and genetic analysis of the PLA2G6 gene. We analysed chronological evolution in terms of age at onset and disease course through a 66-item questionnaire. We performed qualitative and quantitative assessment of MRI abnormalities and searched for clinical and radiological phenotype and genotype correlations. RESULTS: Sixteen PLAN patients (mean age: 10.2 years, range 3-33) were evaluated, with a median onset (years) of signs/symptoms as follows: neurological regression (1.5), oculomotor abnormalities (1.5), hypotonia (1.8), gait loss (2.2), pyramidal signs (3.0), axonal neuropathy (3.0), dysphagia (4.0), optic atrophy (4.0), psychiatric symptoms (4.0), seizures (5.9), joint contractures (6.0), dystonia (8.0), bladder dysfunction (13.0) and parkinsonism (15.0). MRI assessment identified cerebellar atrophy (19/19), brain iron deposition (10/19), clava hypertrophy (8/19) and T2/FLAIR hyperintensity of the cerebellar cortex (6/19). The mid-sagittal vermis relative diameter (MVRD) correlated with age at onset of clinical variants, meaning that the earlier the onset, the more severe the cerebellar atrophy. All patients harboured missense, nonsense and frameshift mutations in PLA2G6, including four novel variants. CONCLUSIONS: Cerebellar atrophy was a universal radiological sign in infantile and childhood onset PLAN, and correlated with the severity of the phenotype. Iron accumulation within the globus pallidum and substantia nigra was also a common and strikingly uniform feature regardless of the phenotype.

Alteraciones reversibles en la neuroimagen asociadas al tratamiento con vigabatrina en lactantes con espasmos epilépticos / Reversible alterations in the neuroimages associated with vigabatrine treatment in infants with epileptic spasms

Introducción. La vigabatrina (VGB) es un fármaco de primera línea para el tratamiento de espasmos infantiles. Diversos estudios han hallado anomalías en la resonancia magnética (RM) cerebral, que afectaban particularmente a los ganglios de la base, y especialmente en secuencias de difusión, en lactantes con espasmos que recibían VGB en altas dosis (> 100 mg/kg/día), y se ha observado la desaparición de las lesiones tras la retirada de dicho tratamiento. Casos clínicos. Se presentan dos casos clínicos con inicio de una encefalopatía epiléptica en el primer año de vida y crisis en forma de espasmos infantiles. Ambos recibieron tratamiento con distintos fármacos, entre ellos VGB hasta dosis de 200 mg/kg/día. Con 11 y 28 meses de vida, respectivamente, aparecían imágenes en la RM cerebral con una marcada hiperintensidad de señal en secuencias ponderadas en T2 en ambos pálidos, tálamos, porción posterior del tronco encefálico y núcleos dentados, que asociaban restricción en secuencias de difusión. Ambos disponían de estudios previos de RM, sin alteraciones. Tras excluir una metabolopatía subyacente, se decidió la retirada de la VGB y tres meses después, en una RM de control, se apreció la total reversibilidad de dichas lesiones. Conclusiones. Deben evaluarse con cautela los hallazgos de la RM cerebral en lactantes que reciban VGB en altas dosis para el tratamiento de espasmos. Su aparente efecto citotóxico sobre los ganglios de la base podría simular metabolopatías/ enfermedades mitocondriales. Conocer este efecto de la VGB y sus características típicas en la RM puede evitar pruebas innecesarias, como una biopsia muscular o un nuevo cribado metabólico (AU)

Introduction. Vigabatrin (VGB) is a first-line drug for the treatment of infantile spasms. Recently, several reports claim the existence of abnormalities in magnetic resonance imaging (MRI) (particularly affecting basal ganglia, and visible in T2 and diffusion sequences) in infants with spasms that were receiving high doses of VGB (> 100 mg/kg/day), which appear to be reversible after withdrawal of treatment. Case reports. We present two cases with an epileptic encephalopathy in the first year of life and seizures consisting of infantile spasms. Both were treated with several antiepileptic drugs, including VGB up to a maximum dosage of 200 mg/ kg/day. At the age of 11 and 28 months, respectively, MRI images showed marked signal hyperintensities on T2-sequences on bilateral globus pallidus, thalamus, posterior portion of the brainstem and dentate nuclei, also visible on diffusion sequences. Both had previous unaltered MRI studies. After excluding an underlying metabolic disease, VGB withdrawal is decided, appreciating the reversibility of those lesions in a prospective MRI study, three months later. Conclusions. We must consider and carefully evaluate findings on brain MRI in infants receiving VGB at high doses for treatment of spasms. The apparent cytotoxic effect on basal ganglia could simulate metabolic/mitochondrial diseases. By knowing this effect of VGB and its typical MRI features, unnecessary testing can be avoided in young infants with epileptic encephalopathies, including complex procedures like muscle biopsy or a new metabolic screening (AU)