WWOX developmental and epileptic encephalopathy: Understanding the epileptology and the mortality risk.

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.

New insights into -related Joubert syndrome.

Purpose: 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, .

Methods: We selected 53 patients with pathogenic variants on , compiled and analysed their clinical, neuroimaging and genetic information and compared it to previous literature.

Results: 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.

The recurrent TCF4 missense variant p.(Arg389Cys) causes a neurodevelopmental disorder overlapping with but not typical for Pitt-Hopkins syndrome.

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.

Tremor-like subcortical myoclonus in STXBP1 encephalopathy.

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.

Biallelic PDE2A variants: a new cause of syndromic paroxysmal dyskinesia.

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.

IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Purpose: 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.

Methods: 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.

Epileptic patients with de novo STXBP1 mutations: Key clinical features based on 24 cases.

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.

Validation of high-resolution DNA melting analysis for mutation scanning of the CDKL5 gene: identification of novel mutations.

Mutations in the cyclin-dependent kinase-like 5 gene (CDKL5) have been predominantly described in epileptic encephalopathies of female, including infantile spasms with Rett-like features. Up to now, detection of mutations in this gene was made by laborious, expensive and/or time consuming methods. Here, we decided to validate high-resolution melting analysis (HRMA) for mutation scanning of the CDKL5 gene.