Cause of complex dyskinesia remains elusive in some patients. A homozygous missense variant leading to drastic decrease of PDE2A enzymatic activity was reported in one patient with childhood-onset ...choreodystonia preceded by paroxysmal dyskinesia and associated with cognitive impairment and interictal EEG abnormalities. Here, we report three new cases with biallelic PDE2A variants identified by trio whole-exome sequencing. Mitochondria network was analyzed after Mitotracker™ Red staining in control and mutated primary fibroblasts. Analysis of retrospective video of patients' movement disorder and refinement of phenotype was carried out. We identified a homozygous gain of stop codon variant c.1180C>T; p.(Gln394*) in PDE2A in siblings and compound heterozygous variants in young adult: a missense c.446C>T; p.(Pro149Leu) and splice-site variant c.1922+5G>A predicted and shown to produce an out of frame transcript lacking exon 22. All three patients had cognitive impairment or developmental delay. The phenotype of the two oldest patients, aged 9 and 26, was characterized by childhood-onset refractory paroxysmal dyskinesia initially misdiagnosed as epilepsy due to interictal EEG abnormalities. The youngest patient showed a proven epilepsy at the age of 4 months and no paroxysmal dyskinesia at 15 months. Interestingly, analysis of the fibroblasts with the biallelic variants in PDE2A variants revealed mitochondria network morphology changes. Together with previously reported case, our three patients confirm that biallelic PDE2A variants are a cause of childhood-onset refractory paroxysmal dyskinesia with cognitive impairment, sometimes associated with choreodystonia and interictal baseline EEG abnormalities or epilepsy.
DYRK1A syndrome is among the most frequent monogenic forms of intellectual disability (ID). We refined the molecular and clinical description of this disorder and developed tools to improve ...interpretation of missense variants, which remains a major challenge in human genetics.
We reported clinical and molecular data for 50 individuals with ID harboring DYRK1A variants and developed (1) a specific DYRK1A clinical score; (2) amino acid conservation data generated from 100 DYRK1A sequences across different taxa; (3) in vitro overexpression assays to study level, cellular localization, and kinase activity of DYRK1A mutant proteins; and (4) a specific blood DNA methylation signature.
This integrative approach was successful to reclassify several variants as pathogenic. However, we questioned the involvement of some others, such as p.Thr588Asn, still reported as likely pathogenic, and showed it does not cause an obvious phenotype in mice.
Our study demonstrated the need for caution when interpreting variants in DYRK1A, even those occurring de novo. The tools developed will be useful to interpret accurately the variants identified in the future in this gene.
In this study, we describe the phenotype and genotype of the largest cohort of patients with Joubert syndrome (JS) carrying pathogenic variants on one of the most frequent causative genes,
.
We ...selected 53 patients with pathogenic variants on
, compiled and analysed their clinical, neuroimaging and genetic information and compared it to previous literature.
Developmental delay (motor and language) was nearly constant but patients had normal intellectual efficiency in 74% of cases (20/27 patients) and 68% followed mainstream schooling despite learning difficulties. Epilepsy was found in only 13% of cases. Only three patients had kidney cysts, only three had genuine retinal dystrophy and no subject had liver fibrosis or polydactyly. Brain MRIs showed typical signs of JS with rare additional features. Genotype-phenotype correlation findings demonstrate a homozygous truncating variant p.Arg950* linked to a more severe phenotype.
This study contradicts previous literature stating an association between
-related JS and ventriculomegaly. Our study implies that
-related JS is linked to positive neurodevelopmental outcome and low rate of other organ defects except for homozygous pathogenic variant p.Arg950*. This information will help modulate patient follow-up and provide families with accurate genetic counselling.
The phenotypic spectrum of STXBP1-related encephalopathy ranges from infantile epileptic encephalopathy to intellectual disability with nonsyndromic or absent epilepsy. Although being frequently ...reported, the tremor associated with STXBP1 has not been fully characterized to date. The aim of our study was to describe it. We recruited patients with intellectual disability due to STXBP1 variants, regardless of their epileptic phenotype, who had tremor at examination and who underwent neurophysiological testing including polymyographic registration of upper limbs muscles activity at rest, during posture maintenance and action. Six patients met the inclusion criteria over four years. Clinically, all had a postural and action distal tremor increased by emotions. Neurophysiological recordings showed a specific myoclonus pattern and were highly suggestive of a subcortical generator. The tremor-like observed in STXBP1 encephalopathy is due to a subcortical pseudo-rhythmic myoclonus.
•The phenotypic spectrum of STXBP1-related encephalopathy ranges from infantile epileptic encephalopathies to intellectual disability with non-syndromic or absent epilepsy. Although being frequently reported, the tremor associated with STXBP1 has not been fully described yet. We aimed at describing this tremor clinically and at addressing the question of its nature and origin.•To reach this goal, we recruited over four years six patients with STXBP1-related intellectual deficiency and tremor, regardless of their epileptic phenotype. All patients underwent polymyographic recording of upper limbs muscles activity at rest, during posture maintenance and action, completed with cortical recording.•We found that all patients displayed a distal or proximo-distal tremor-like irregular rhythmic myoclonus during posture maintenance and action, with a very likely subcortical generator.•Thus, we show for the first time that the “tremor” reported in many patients with STXBP1 encephalopathy is actually a pseudo-rhythmic subcortical myoclonus.•This result is of particular interest for the readers of European Journal of Paediatric Neurology since 1) the nature of the pseudo-tremor of STXBP1 encephalopathy was ignored, 2) its subcortical origin has therapeutic consequences.
Autosomal recessive microcephaly or microcephaly primary hereditary (MCPH) is a genetically heterogeneous neurodevelopmental disorder characterized by a reduction in brain volume, indirectly measured ...by an occipitofrontal circumference (OFC) 2 standard deviations or more below the age‐ and sex‐matched mean (−2SD) at birth and −3SD after 6 months, and leading to intellectual disability of variable severity. The abnormal spindle‐like microcephaly gene (ASPM), the human ortholog of the Drosophila melanogaster “abnormal spindle” gene (asp), encodes ASPM, a protein localized at the centrosome of apical neuroprogenitor cells and involved in spindle pole positioning during neurogenesis. Loss‐of‐function mutations in ASPM cause MCPH5, which affects the majority of all MCPH patients worldwide. Here, we report 47 unpublished patients from 39 families carrying 28 new ASPM mutations, and conduct an exhaustive review of the molecular, clinical, neuroradiological, and neuropsychological features of the 282 families previously reported (with 161 distinct ASPM mutations). Furthermore, we show that ASPM‐related microcephaly is not systematically associated with intellectual deficiency and discuss the association between the structural brain defects (strong reduction in cortical volume and surface area) that modify the cortical map of these patients and their cognitive abilities.
Loss‐of‐function mutations in the Abnormal SPindle‐like Microcephaly gene (ASPM) cause MicroCephaly Primary Hereditary (MCPH) type 5, defined by reduced brain volumes associated with intellectual disability. We compiled the molecular, clinical, neuroradiological and neuropsychological features of 47 patients (39 families, 28 novel mutations), and reviewed those of 282 previously reported families. We report that ASPM‐related microcephaly is not systematically associated with intellectual deficiency and discuss the association between structural brain defects (strongly reduced cortical volume and surface area) and cognitive abilities.
TCF4 haploinsufficiency by deletions, truncating variants or loss‐of‐function missense variants within the DNA‐binding and protein interacting bHLH domain causes Pitt‐Hopkins syndrome (PTHS). This ...neurodevelopmental disorder (NDD) is characterized by severe intellectual disability (ID), epilepsy, hyperbreathing and a typical facial gestalt. Only few aberrations of the N‐terminus of TCF4 were associated with milder or atypical phenotypes. By personal communication and searching databases we assembled six cases with the novel, recurrent, de novo missense variant c.1165C > T, p.(Arg389Cys) in TCF4. This variant was identified by diagnostic exome or panel sequencing and is located upstream of the bHLH domain. All six individuals presented with moderate to severe ID with language impairment. Microcephaly occurred in two individuals, epilepsy only in one, and no breathing anomalies or myopia were reported. Facial gestalt showed some aspects of PTHS but was rather non‐specific in most individuals. Interestingly, the variant is located within the AD2 activation domain next to a highly conserved coactivator‐recruitment motif and might alter interaction with coactivator proteins independently from the bHLH domain. Our findings of a recurrent missense variant outside the bHLH domain in six individuals with an ID phenotype overlapping with but not typical for PTHS delineate a novel genotype–phenotype correlation for TCF4‐related NDDs.
Objective
WWOX is an autosomal recessive cause of early infantile developmental and epileptic encephalopathy (WWOX‐DEE), also known as WOREE (WWOX‐related epileptic encephalopathy). We analyzed the ...epileptology and imaging features of WWOX‐DEE, and investigated genotype–phenotype correlations, particularly with regard to survival.
Methods
We studied 13 patients from 12 families with WWOX‐DEE. Information regarding seizure semiology, comorbidities, facial dysmorphisms, and disease outcome were collected. Electroencephalographic (EEG) and brain magnetic resonance imaging (MRI) data were analyzed. Pathogenic WWOX variants from our cohort and the literature were coded as either null or missense, allowing individuals to be classified into one of three genotype classes: (1) null/null, (2) null/missense, (3) missense/missense. Differences in survival outcome were estimated using the Kaplan–Meier method.
Results
All patients experienced multiple seizure types (median onset = 5 weeks, range = 1 day–10 months), the most frequent being focal (85%), epileptic spasms (77%), and tonic seizures (69%). Ictal EEG recordings in six of 13 patients showed tonic (n = 5), myoclonic (n = 2), epileptic spasms (n = 2), focal (n = 1), and migrating focal (n = 1) seizures. Interictal EEGs demonstrated slow background activity with multifocal discharges, predominantly over frontal or temporo‐occipital regions. Eleven of 13 patients had a movement disorder, most frequently dystonia. Brain MRIs revealed severe frontotemporal, hippocampal, and optic atrophy, thin corpus callosum, and white matter signal abnormalities. Pathogenic variants were located throughout WWOX and comprised both missense and null changes including five copy number variants (four deletions, one duplication). Survival analyses showed that patients with two null variants are at higher mortality risk (p‐value = .0085, log‐rank test).
Significance
Biallelic WWOX pathogenic variants cause an early infantile developmental and epileptic encephalopathy syndrome. The most common seizure types are focal seizures and epileptic spasms. Mortality risk is associated with mutation type; patients with biallelic null WWOX pathogenic variants have significantly lower survival probability compared to those carrying at least one presumed hypomorphic missense pathogenic variant.
Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences.
We collected the ...data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms.
IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments.
This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.
Summary
Objective
Mutations in the syntaxin binding protein 1 gene (STXBP1) have been associated mostly with early onset epileptic encephalopathies (EOEEs) and Ohtahara syndrome, with a mutation ...detection rate of approximately 10%, depending on the criteria of selection of patients. The aim of this study was to retrospectively describe clinical and electroencephalography (EEG) features associated with STXBP1‐related epilepsies to orient molecular screening.
Methods
We screened STXBP1 in a cohort of 284 patients with epilepsy associated with a developmental delay/intellectual disability and brain magnetic resonance imaging (MRI) without any obvious structural abnormality. We reported on patients with a mutation and a microdeletion involving STXBP1 found using array comparative genomic hybridization (CGH).
Results
We found a mutation of STXBP1 in 22 patients and included 2 additional patients with a deletion including STXBP1. In 22 of them, epilepsy onset was before 3 months of age. EEG at onset was abnormal in all patients, suppression‐burst and multifocal abnormalities being the most common patterns. The rate of patients carrying a mutation ranged from 25% in Ohtahara syndrome to <5% in patients with an epilepsy beginning after 3 months of age. Epilepsy improved over time for most patients, with an evolution to West syndrome in half. Patients had moderate to severe developmental delay with normal head growth. Cerebellar syndrome with ataxic gait and/or tremor was present in 60%.
Significance
Our data confirm that STXBP1 mutations are associated with neonatal‐infantile epileptic encephalopathies. The initial key features highlighted in the cohort of early epileptic patients are motor seizures either focal or generalized, abnormal initial interictal EEG, and normal head growth. In addition, we constantly found an ongoing moderate to severe developmental delay with normal head growth. Patients often had ongoing ataxic gait with trembling gestures. Altogether these features should help the clinician to consider STXBP1 molecular screening.
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