Fragile Females: Case Series of Epilepsy in Girls With FMR1 Disruption

Sulthiame use in children with pharmacoresistant epilepsies: A retrospective study

OBJECTIVE

This retrospective study aimed to assess the efficacy and tolerability of sulthiame as an add-on treatment in children with pharmacoresistant epilepsies.

METHODS

All patients with epilepsy who received sulthiame at Montreal Children's Hospital over an 11-year period were included. Medical charts were reviewed, and extracted data included patient age and sex, seizure types, epilepsy syndrome, electroencephalography (EEG) reports, brain imaging reports, antiseizure treatments trialed, starting and final dose of sulthiame, duration of sulthiame treatment, adverse events attributed to sulthiame, and seizure frequency before and after sulthiame treatment. EEG studies were also analyzed and spike-wave index (SWI) in the first 10 min of sleep was calculated.

RESULTS

Sixteen patients were included, all of whom had pharmacoresistant epilepsies (mean of 9.9 trials of other antiseizure treatments). Six had genetic diagnoses, four had in utero/perinatal acquired brain injury, one had a suspected focal cortical dysplasia, and five were idiopathic. Ten patients had developmental and epileptic encephalopathy with spike-wave activation in sleep, three had Lennox-Gastaut syndrome, and one each had sleep-related hyperkinetic epilepsy, self-limited epilepsy with centrotemporal spikes, and mixed generalized and multifocal epilepsy. Of the 12 patients with uncontrolled seizures at the time of sulthiame initiation, 4 had improvement in seizure frequency, including 2 who became seizure free. Eight patients had EEG data available that allowed calculation of sleep SWI; from this group, SWI decreased from 81.1% +/- 17.6% to 45.1% +/- 36.5% (p = .007). The most common adverse events reported were somnolence/drowsiness, aggression, and increased seizure frequency. Of the patients with genetic etiologies, significant positive responses were seen in patients with pathogenic variants in NDUFS1 and SATB1.

SIGNIFICANCE

These data demonstrate the therapeutic potential of sulthiame, even in patients with highly pharmacoresistant epilepsy. Improvements may be seen in both seizure frequency and sleep SWI.

De Novo Large Deletion Leading to Fragile X Syndrome

Fragile X syndrome (FXS) is the most frequent cause of X-linked inherited intellectual disabilities (ID) and the most frequent monogenic form of autism spectrum disorders. It is caused by an expansion of a CGG trinucleotide repeat located in the 5'UTR of the FMR1 gene, resulting in the absence of the fragile X mental retardation protein, FMRP. Other mechanisms such as deletions or point mutations of the FMR1 gene have been described and account for approximately 1% of individuals with FXS. Here, we report a 7-year-old boy with FXS with a de novo deletion of approximately 1.1 Mb encompassing several genes, including the FMR1 and the ASFMR1 genes, and several miRNAs, whose lack of function could result in the observed proband phenotypes. In addition, we also demonstrate that FMR4 completely overlaps with ASFMR1, and there are no sequencing differences between both transcripts (i.e., ASFMR1/FMR4 throughout the article).

GC-rich repeat expansions: associated disorders and mechanisms

Noncoding repeat expansions are a well-known cause of genetic disorders mainly affecting the central nervous system. Missed by most standard technologies used in routine diagnosis, pathogenic noncoding repeat expansions have to be searched for using specific techniques such as repeat-primed PCR or specific bioinformatics tools applied to genome data, such as ExpansionHunter. In this review, we focus on GC-rich repeat expansions, which represent at least one third of all noncoding repeat expansions described so far. GC-rich expansions are mainly located in regulatory regions (promoter, 5' untranslated region, first intron) of genes and can lead to either a toxic gain-of-function mediated by RNA toxicity and/or repeat-associated non-AUG (RAN) translation, or a loss-of-function of the associated gene, depending on their size and their methylation status. We herein review the clinical and molecular characteristics of disorders associated with these difficult-to-detect expansions.

Beyond Trinucleotide Repeat Expansion in Fragile X Syndrome: Rare Coding and Noncoding Variants in FMR1 and Associated Phenotypes

FMR1 (FMRP translational regulator 1) variants other than repeat expansion are known to cause disease phenotypes but can be overlooked if they are not accounted for in genetic testing strategies. We collected and reanalyzed the evidence for pathogenicity of FMR1 coding, noncoding, and copy number variants published to date. There is a spectrum of disease-causing FMR1 variation, with clinical and functional evidence supporting pathogenicity of five splicing, five missense, one in-frame deletion, one nonsense, and four frameshift variants. In addition, FMR1 deletions occur in both mosaic full mutation patients and as constitutional pathogenic alleles. De novo deletions arise not only from full mutation alleles but also alleles with normal-sized CGG repeats in several patients, suggesting that the CGG repeat region may be prone to genomic instability even in the absence of repeat expansion. We conclude that clinical tests for potentially FMR1-related indications such as intellectual disability should include methods capable of detecting small coding, noncoding, and copy number variants.

Genetic diagnosis of infantile-onset epilepsy in the clinic: Application of whole-exome sequencing following epilepsy gene panel testing

This study aimed to evaluate the clinical utility of whole-exome sequencing in a group of infantile-onset epilepsy patients who tested negative for epilepsy using a gene panel test. Whole-exome sequencing was performed on 59 patients who tested negative on customized epilepsy gene panel testing. We identified eight pathogenic or likely pathogenic sequence variants in eight different genes (FARS2, YWHAG, KCNC1, DYRK1A, SMC1A, PIGA, OGT, and FGF12), one pathogenic structural variant (8.6 Mb-sized deletion on chromosome X [140 994 419-149 630 805]), and three putative low-frequency mosaic variants from three different genes (GABBR2, MTOR, and CUX1). Subsequent whole-exome sequencing revealed an additional 8% of diagnostic yield with genetic confirmation of epilepsy in 55.4% (62/112) of our cohort. Three genes (YWHAG, KCNC1, and FGF12) were identified as epilepsy-causing genes after the original gene panel was designed. The others were initially linked with mitochondrial encephalopathy or different neurodevelopmental disorders, although an epilepsy phenotype was listed as one of the clinical features. Application of whole-exome sequencing following epilepsy gene panel testing provided 8% of additional diagnostic yield in an infantile-onset epilepsy cohort. Whole-exome sequencing could provide an opportunity to reanalyze newly recognized epilepsy-linked genes without updating the gene panel design.

Seizures in Fragile X Syndrome: Associations and Longitudinal Analysis of a Large Clinic-Based Cohort

Fragile X syndrome (FXS), the most common inherited cause of intellectual disability, learning disability, and autism spectrum disorder, is associated with an increased prevalence of certain medical conditions including seizures. The goal of this study was to better understand seizures in individuals with FXS using the Fragile X Online Registry with Accessible Research Database, a multisite observational study initiated in 2012 involving FXS clinics in the Fragile X Clinic and Research Consortium. Seizure data were available for 1,607 participants, mostly male (77%) and white (74.5%). The overall prevalence of at least one seizure was 12%, with this rate being significantly higher in males than females (13.7 vs. 6.2%, p < 0.001). As compared to individuals with FXS without seizures, those with seizures were more likely to have autism spectrum disorder, current sleep apnea, later acquisition of expressive language, more severe intellectual disability, hyperactivity, irritability, and stereotyped movements. The mean age of seizure onset was 6.4 (SD 6.1) years of age with the great majority (>80%) having onset of seizures which was before 10. For those with epilepsy, about half (52%) had seizures for more than 3 years. This group was found to have greater cognitive and language impairment, but not behavioral disruptions, compared with those with seizures for <3 years. Antiepileptic drugs were more often used in males (60.6%) than females (34.8%), and females more often required more than one medication. The most commonly used anticonvulsants were oxcarbazepine, valproic acid, lamotrigine, and levetiracetam. The current study is the largest and first longitudinal study ever conducted to describe seizures in FXS. Overall, this study confirms previous reports of seizures in FXS and extends previous findings by further defining the cognitive and behavioral phenotype of those with epilepsy in FXS. Future studies should further investigate the natural history of seizures in FXS and the characteristics of seizures in FXS in adulthood.