Neurologic complications of thiamine (B1) deficiency following bariatric surgery in adolescents

BACKGROUND

The prevalence of obesity among children and adolescents is rising and poses a major health concern. Bariatric surgery is well established in adults and has become an option for adolescents. Thiamine (B1) deficiency is common following bariatric surgery in adults. It may present as Beri-Beri, Wernicke encephalopathy, or Korsakoff psychosis.

OBJECTIVE

Our aim was to describe the clinical features, diagnosis, and treatment of adolescents who presented with B1 deficiency after bariatric surgery at one center, and to summarize the data from the literature.

PATIENTS

Three adolescents with morbid obesity (two boys and one girl, aged 15.5 to- 17-years-old), presented at Schneider Children's Medical Center of Israel with progressive lower limb pain and weakness 2-3 month following a bariatric procedure (sleeve gastrectomy or narrowing of a bariatric band). The girl also had upper limb involvement and cerebellar signs. All three were non-compliant with micronutrient supplementation. After admission, they received intravenous B1 and oral multivitamin supplementation, and their symptoms improved considerably.

CONCLUSIONS

Micronutrient supplementation following bariatric surgery is crucial to prevent deficiencies. In adolescents, compliance with micronutrient supplementation should be assessed before and after such surgery. Thiamine deficiency may cause polyneuropathy, among other symptoms. Treatment reduces the severity of neurological complications.

BRAT1-related disorders: phenotypic spectrum and phenotype-genotype correlations from 97 patients

BRAT1 biallelic variants are associated with rigidity and multifocal seizure syndrome, lethal neonatal (RMFSL), and neurodevelopmental disorder associating cerebellar atrophy with or without seizures syndrome (NEDCAS). To date, forty individuals have been reported in the literature. We collected clinical and molecular data from 57 additional cases allowing us to study a large cohort of 97 individuals and draw phenotype-genotype correlations. Fifty-nine individuals presented with BRAT1-related RMFSL phenotype. Most of them had no psychomotor acquisition (100%), epilepsy (100%), microcephaly (91%), limb rigidity (93%), and died prematurely (93%). Thirty-eight individuals presented a non-lethal phenotype of BRAT1-related NEDCAS phenotype. Seventy-six percent of the patients in this group were able to walk and 68% were able to say at least a few words. Most of them had cerebellar ataxia (82%), axial hypotonia (79%) and cerebellar atrophy (100%). Genotype-phenotype correlations in our cohort revealed that biallelic nonsense, frameshift or inframe deletion/insertion variants result in the severe BRAT1-related RMFSL phenotype (46/46; 100%). In contrast, genotypes with at least one missense were more likely associated with NEDCAS (28/34; 82%). The phenotype of patients carrying splice variants was variable: 41% presented with RMFSL (7/17) and 59% with NEDCAS (10/17).

Infant Botulism, Israel, 2007-2021

Infant botulism (IB) is an intestinal toxemia that manifests as descending paralysis, constipation, and, in some cases, respiratory failure. Laboratory-confirmed IB cases are rare, and recent data in Israel are lacking. We conducted a national multicenter retrospective study of laboratory-confirmed IB cases reported in Israel during 2007-2021. A total of 8 cases were reported during the study period. During 2019-2021, incidence may have increased because of a cluster of 5 cases. Infant median age for diagnosis was 6.5 months, older than previously reported (3 months). Most cases occurred during March-July. Honey consumption was reported in 1 case, and possible environmental risk factors (living nearby rural or construction areas, dust exposure, and having a father who works as a farmer) were reported in 6 cases. Although IB is rare, its incidence in Israel may have increased over recent years, and its epidemiology and risk factors differ from cases reported previously in Israel.

Clinical improvement of a toddler with COVID-19 focal cerebral arteriopathy possibly due to intra-arterial nimodipine

Pediatric stroke is considered an infrequent complication of COVID-19. Focal cerebral arteriopathy (FCA) is one of the most common causes of arterial ischemic stroke in a previously healthy child. The present report describes a toddler with FCA most likely induced by SARS-CoV-2 infection who showed significant clinical improvement that may be related to injection of intra-arterial nimodipine. To our knowledge, this is the first reported use of nimodipine in this setting.

Rheumatic fever in a developed country - is it still relevant? A retrospective, 25 years follow-up

BACKGROUND

Our aims were to clinically and epidemiologically characterize rheumatic fever (RF) in the current era in Israel. Although there has been a steady decline in the incidence of RF in the western world, evidence of disease resurgence in developed countries continues to be published. The paucity of recent epidemiological data prompted our study.

METHODS

Medical files were retrospectively reviewed for all children with RF in our tertiary pediatric university-affiliated hospital from 1993 to 2017. Main outcome measures were patients and disease related characteristics, incidence trends, risk factors, disease course, relapse rates and secondary prophylaxis.

RESULTS

The cohort included 307 children. Sixty-four percent presented with arthritis, interestingly including hips and small joints of hands and feet at presentation, 52% presented with carditis. Severe carditis developed in 31 patients (19.5%), of whom 21 (13.2% of all carditis patients) acquired heart failure, 5 required intensive care monitoring, with one recent death. The percentage of patients with acute carditis of the overall RF patients remained relatively stable. Thirty-two patients (10% of patients with RF) relapsed, including 11 with a cardiac relapse (3.6% of all cardiac patients). The recurrence rate of RF continued to rise up to 9 years from the initial episode. One of 147 patients (< 0.7%) with a non-cardiac initial presentation had carditis at relapse.

CONCLUSION

RF and rheumatic heart disease remain an important cause of morbidity and mortality including developed countries, with relapse rate continuing after 9 years of prophylaxis. Presentation of small joints as well as hips, although uncommon, should not exclude the diagnosis.

The phenotype of homozygous EMC10 variant: A new syndrome with intellectual disability and language impairment

AIM

To explore the cognitive and behavioral phenotype associated with a recently reported variant in endoplasmic reticulum membrane complex EMC10 c.287delG (Gly96Alafs∗9), suggested to cause a novel syndromic neurodevelopmental disorder.

METHODS

Homozygous EMC10 variant identified by a combination of autozygosity mapping and exome sequencing was found in five children (aged 7-18) from a large extended family. Their functioning was compared to normative data as well as to that of age-matched relatives (siblings/cousins), sharing similar familial and demographic characteristics. Neuropsychological, behavioral, and daily functioning were assessed.

RESULTS

Performance of all participants with EMC10 variant on both cognitive functioning and adaptive skills was lower than the normal range fulfilling diagnostic criteria for intellectual disability. Their functioning was also lower than that of their matched relatives on most areas of functioning, except visual memory that was found higher, in the low average range. Language difficulty was apparent in all participants with EMC10, and a discrepancy within participants' phenotype was found, with lower verbal abilities compared to visuospatial ability. More behavioral problems were found, although not in all participants with EMC10.

CONCLUSION

Homozygous EMC10 variant was found associated with a phenotype of intellectual disability and language deficits.

A recurrent, homozygous EMC10 frameshift variant is associated with a syndrome of developmental delay with variable seizures and dysmorphic features

PURPOSE

The endoplasmic reticulum membrane complex (EMC) is a highly conserved, multifunctional 10-protein complex related to membrane protein biology. In seven families, we identified 13 individuals with highly overlapping phenotypes who harbor a single identical homozygous frameshift variant in EMC10.

METHODS

Using exome, genome, and Sanger sequencing, a recurrent frameshift EMC10 variant was identified in affected individuals in an international cohort of consanguineous families. Multiple families were independently identified and connected via Matchmaker Exchange and internal databases. We assessed the effect of the frameshift variant on EMC10 RNA and protein expression and evaluated EMC10 expression in normal human brain tissue using immunohistochemistry.

RESULTS

A homozygous variant EMC10 c.287delG (Refseq NM_206538.3, p.Gly96Alafs*9) segregated with affected individuals in each family, who exhibited a phenotypic spectrum of intellectual disability (ID) and global developmental delay (GDD), variable seizures and variable dysmorphic features (elongated face, curly hair, cubitus valgus, and arachnodactyly). The variant arose on two founder haplotypes and results in significantly reduced EMC10 RNA expression and an unstable truncated EMC10 protein.

CONCLUSION

We propose that a homozygous loss-of-function variant in EMC10 causes a novel syndromic neurodevelopmental phenotype. Remarkably, the recurrent variant is likely the result of a hypermutable site and arose on distinct founder haplotypes.

The murine ortholog of Kaufman oculocerebrofacial syndrome protein Ube3b regulates synapse number by ubiquitinating Ppp3cc

Kaufman oculocerebrofacial syndrome (KOS) is a severe autosomal recessive disorder characterized by intellectual disability, developmental delays, microcephaly, and characteristic dysmorphisms. Biallelic mutations of UBE3B, encoding for a ubiquitin ligase E3B are causative for KOS. In this report, we characterize neuronal functions of its murine ortholog Ube3b and show that Ube3b regulates dendritic branching in a cell-autonomous manner. Moreover, Ube3b knockout (KO) neurons exhibit increased density and aberrant morphology of dendritic spines, altered synaptic physiology, and changes in hippocampal circuit activity. Dorsal forebrain-specific Ube3b KO animals show impaired spatial learning, altered social interactions, and repetitive behaviors. We further demonstrate that Ube3b ubiquitinates the catalytic γ-subunit of calcineurin, Ppp3cc, the overexpression of which phenocopies Ube3b loss with regard to dendritic spine density. This work provides insights into the molecular pathologies underlying intellectual disability-like phenotypes in a genetically engineered mouse model.

A New Mechanism in THRA Resistance: The First Disease-Associated Variant Leading to an Increased Inhibitory Function of THRA2

The nuclear thyroid hormone receptors (THRs) are key mediators of thyroid hormone function on the cellular level via modulation of gene expression. Two different genes encode THRs (THRA and THRB), and are pleiotropically involved in development, metabolism, and growth. The THRA1 and THRA2 isoforms, which result from alternative splicing of THRA, differ in their C-terminal ligand-binding domain (LBD). Most published disease-associated THRA variants are located in the LBD of THRA1 and impede triiodothyronine (T3) binding. This keeps the nuclear receptor in an inactive state and inhibits target gene expression. Here, we investigated a new dominant THRA variant (chr17:g.38,241,010A > G, GRCh37.13 | c.518A > G, NM_199334 | p.(E173G), NP_955366), which is located between the DNA- and ligand-binding domains and affects both splicing isoforms. Patients presented partially with hypothyroid (intellectual disability, motor developmental delay, brain atrophy, and constipation) and partially with hyperthyroid symptoms (tachycardia and behavioral abnormalities) to varying degrees. Functional characterization of THRA1p.(E173G) by reporter gene assays revealed increased transcriptional activity in contrast to THRA1(WT), unexpectedly revealing the first gain-of-function mutation found in THRA1. The THRA2 isoform does not bind T3 and antagonizes THRA1 action. Introduction of p.(E173G) into THRA2 increased its inhibitory effect on THRA1, which helps to explain the hypothyroid symptoms seen in our patients. We used protein structure models to investigate possible underlying pathomechanisms of this variant with a gain-of-antagonistic function and suggest that the p.(E173G) variant may have an influence on the dimerization domain of the nuclear receptor.

Association of pediatric idiopathic intracranial hypertension with olfactory performance

OBJECTIVE

To assess the association between pediatric Idiopathic intracranial hypertension (IIH) and olfactory performance.

METHODS

A cross-sectional comparative study was conducted including 17 patients under 18 years diagnosed with IIH at a tertiary hospital and 17 healthy age- and sex-matched subjects. All participants underwent the semi-objective chemosensory Sniffin' Sticks test for evaluation of odor threshold (OT), indicative of peripheral olfactory function, and odor identification (OI), reflecting higher cognitive olfactory processing. Scores were compared and referred to the updated normative values. Demographic, clinical, and neuroimaging data were collected from the medical files. The patients with IIH were reassessed for olfactory function and clinical state at the subsequent follow-up, under treatment.

RESULTS

Compared to controls, the IIH group had a significantly lower mean OT score (6.41 ± 3.43 vs 10.21 ± 2.79, p = 0.001) and higher rate of OT score below the 10th percentile for age and sex according to the normative values (47.1% vs 0%, p = 0.001). There was no significant between-group difference in mean OI scores (9.82 ± 1.63, vs 10.59 ± 1.84, p = 0.290). OT scores were not associated with sex, age, body mass index, neuroimaging abnormalities, or lumbar puncture opening pressure. At the follow-up assessment, the OT scores were improved (9.36 ± 4.17 vs 6.7 ± 3.32, p = 0.027) whereas the OI scores were unchanged (9.88 ± 2.5 vs 9.69 ± 1.58, p = 0.432).

CONCLUSIONS

As reported in adults, children and adolescents with IIH appear to have a selective reversible deficit in olfactory detection threshold, which may imply a reduction in peripheral olfactory perceptual ability. Future studies should examine the predictive value of olfactory function for IIH.

Evolution of EEG Findings in Pontocerebellar Hypoplasia Type 2A: Normal EEG in the First Few Months followed by Abnormal Tracing over the Years

Pontocerebellar hypoplasia (PCH) is an autosomal recessive neurodevelopmental and neurodegenerative disorder characterized by cerebellar and pontine hypoplasia, progressive microcephaly, and developmental delay. Ten types of PCH have been described; PCH type 2A (PCH2A) due to a mutation in TSEN54 is the most frequent. Seizures have been reported in the large majority of patients. The probability of epilepsy developing increases with age, along with difficulties in differentiating seizures from dyskinetic movements. The aim of the present report was to describe the clinical symptoms and electroencephalogram (EEG) changes over time in three patients of Israeli Arab origin with PCH2A. All three, including two siblings and their first cousin, were homozygous for the TSEN54 p.A304S mutation. The patients demonstrated profound psychomotor retardation, severe spasticity and contractures, choreoathetoid movements, and seizures. The magnetic resonance imaging (MRI) scans and EEGs were reviewed by an experienced neuroradiologist and epileptologist, respectively. The MRI scans revealed a dragonfly-like cerebellar pattern in all patients. Despite the normal early EEG findings, all patients had characteristic features of epilepsy, with tonic seizures starting in the first days to months followed by focal to bilateral tonic-clonic seizures in early childhood which continued to adolescence. In conclusion, patients with PCH2A due to the missense mutation p.A304S in TSEN54 exhibit profound psychomotor delay, movement disorders, and intractable epilepsy. An evolution of EEG abnormalities and seizure semiology occurs over time. Similar to several other genetic epileptic encephalopathies, the normal early EEG tracing does not rule out the later occurrence of epilepsy.

Variants in SCAF4 Cause a Neurodevelopmental Disorder and Are Associated with Impaired mRNA Processing

RNA polymerase II interacts with various other complexes and factors to ensure correct initiation, elongation, and termination of mRNA transcription. One of these proteins is SR-related CTD-associated factor 4 (SCAF4), which is important for correct usage of polyA sites for mRNA termination. Using exome sequencing and international matchmaking, we identified nine likely pathogenic germline variants in SCAF4 including two splice-site and seven truncating variants, all residing in the N-terminal two thirds of the protein. Eight of these variants occurred de novo, and one was inherited. Affected individuals demonstrated a variable neurodevelopmental disorder characterized by mild intellectual disability, seizures, behavioral abnormalities, and various skeletal and structural anomalies. Paired-end RNA sequencing on blood lymphocytes of SCAF4-deficient individuals revealed a broad deregulation of more than 9,000 genes and significant differential splicing of more than 2,900 genes, indicating an important role of SCAF4 in mRNA processing. Knockdown of the SCAF4 ortholog CG4266 in the model organism Drosophila melanogaster resulted in impaired locomotor function, learning, and short-term memory. Furthermore, we observed an increased number of active zones in larval neuromuscular junctions, representing large glutamatergic synapses. These observations indicate a role of CG4266 in nervous system development and function and support the implication of SCAF4 in neurodevelopmental phenotypes. In summary, our data show that heterozygous, likely gene-disrupting variants in SCAF4 are causative for a variable neurodevelopmental disorder associated with impaired mRNA processing.

A new homozygous HERC1 gain-of-function variant in MDFPMR syndrome leads to mTORC1 hyperactivation and reduced autophagy during cell catabolism

The giant 532 kDa HERC1 protein is a ubiquitin ligase that interacts with tuberous sclerosis complex subunit 2 (TSC2), a negative upstream regulator of the mammalian target of rapamycin complex 1 (mTORC1). TSC2 regulates anabolic cell growth through its influence on protein synthesis, cell growth, proliferation, autophagy, and differentiation. TSC subunit 1 (TSC1) stabilizes TSC2 by inhibiting the interaction between TSC2 and HERC1, forming a TSC1-TSC2 complex that negatively regulates mTORC1. HERC1-TSC2 interaction destabilizes and degrades TSC2. Recessive mutations in HERC1 have been reported in patients with intellectual disability. Some patients exhibit epilepsy, macrocephaly, somatic overgrowth, and dysmorphic facial features as well. Here we describe two sisters from a consanguineous marriage with a novel homozygous missense variant in the C-terminal HECT domain of HERC1 [chr15:g63,907,989C>G GRCh37.p11 | c.14,072G>C NM_003922 | p.(Arg4,691Pro)]. Symptoms compris global developmental delay, macrocephaly, somatic overgrowth, intellectual disability, seizures, schizoaffective disorder, and pyramidal tract signs. We functionally assessed the HERC1 mutation by investigation of patient and control fibroblasts under normal and nutrient starving conditions. During catabolic state, mTORC1 activity remained high in patient fibroblasts, which stands in stark contrast to its downregulation in controls. This was corroborated by an abnormally high phosphorylation of S6K1-kinase, a direct downstream target of mTORC1, in patients. Moreover, autophagy, usually enhanced in catabolic states, was down-regulated in patient fibroblasts. These data confirm that the missense variant found in both patients results in a gain-of-function for the mutant HERC1 protein.

Bi-allelic ADARB1 Variants Associated with Microcephaly, Intellectual Disability, and Seizures

The RNA editing enzyme ADAR2 is essential for the recoding of brain transcripts. Impaired ADAR2 editing leads to early-onset epilepsy and premature death in a mouse model. Here, we report bi-allelic variants in ADARB1, the gene encoding ADAR2, in four unrelated individuals with microcephaly, intellectual disability, and epilepsy. In one individual, a homozygous variant in one of the double-stranded RNA-binding domains (dsRBDs) was identified. In the others, variants were situated in or around the deaminase domain. To evaluate the effects of these variants on ADAR2 enzymatic activity, we performed in vitro assays with recombinant proteins in HEK293T cells and ex vivo assays with fibroblasts derived from one of the individuals. We demonstrate that these ADAR2 variants lead to reduced editing activity on a known ADAR2 substrate. We also demonstrate that one variant leads to changes in splicing of ADARB1 transcript isoforms. These findings reinforce the importance of RNA editing in brain development and introduce ADARB1 as a genetic etiology in individuals with intellectual disability, microcephaly, and epilepsy.

Intronic ATTTC repeat expansions in STARD7 in familial adult myoclonic epilepsy linked to chromosome 2

Familial Adult Myoclonic Epilepsy (FAME) is characterised by cortical myoclonic tremor usually from the second decade of life and overt myoclonic or generalised tonic-clonic seizures. Four independent loci have been implicated in FAME on chromosomes (chr) 2, 3, 5 and 8. Using whole genome sequencing and repeat primed PCR, we provide evidence that chr2-linked FAME (FAME2) is caused by an expansion of an ATTTC pentamer within the first intron of STARD7. The ATTTC expansions segregate in 158/158 individuals typically affected by FAME from 22 pedigrees including 16 previously reported families recruited worldwide. RNA sequencing from patient derived fibroblasts shows no accumulation of the AUUUU or AUUUC repeat sequences and STARD7 gene expression is not affected. These data, in combination with other genes bearing similar mutations that have been implicated in FAME, suggest ATTTC expansions may cause this disorder, irrespective of the genomic locus involved.

Clinical, Biomarker, and Molecular Delineations and Genotype-Phenotype Correlations of Ataxia With Oculomotor Apraxia Type 1

Importance

Ataxia with oculomotor apraxia type 1 (AOA1) is an autosomal recessive cerebellar ataxia due to mutations in the aprataxin gene (APTX) that is characterized by early-onset cerebellar ataxia, oculomotor apraxia, axonal motor neuropathy, and eventual decrease of albumin serum levels.

Objectives

To improve the clinical, biomarker, and molecular delineation of AOA1 and provide genotype-phenotype correlations.

Design, Setting, and Participants

This retrospective analysis included the clinical, biological (especially regarding biomarkers of the disease), electrophysiologic, imaging, and molecular data of all patients consecutively diagnosed with AOA1 in a single genetics laboratory from January 1, 2002, through December 31, 2014. Data were analyzed from January 1, 2015, through January 31, 2016.

Main Outcomes and Measures

The clinical, biological, and molecular spectrum of AOA1 and genotype-phenotype correlations.

Results

The diagnosis of AOA1 was confirmed in 80 patients (46 men [58%] and 34 women [42%]; mean [SD] age at onset, 7.7 [7.4] years) from 51 families, including 57 new (with 8 new mutations) and 23 previously described patients. Elevated levels of α-fetoprotein (AFP) were found in 33 patients (41%); hypoalbuminemia, in 50 (63%). Median AFP level was higher in patients with AOA1 (6.0 ng/mL; range, 1.1-17.0 ng/mL) than in patients without ataxia (3.4 ng/mL; range, 0.8-17.2 ng/mL; P < .01). Decreased albumin levels (ρ = -0.532) and elevated AFP levels (ρ = 0.637) were correlated with disease duration. The p.Trp279* mutation, initially reported as restricted to the Portuguese founder haplotype, was discovered in 53 patients with AOA1 (66%) with broad white racial origins. Oculomotor apraxia was found in 49 patients (61%); polyneuropathy, in 74 (93%); and cerebellar atrophy, in 78 (98%). Oculomotor apraxia correlated with the severity of ataxia and mutation type, being more frequent with deletion or truncating mutations (83%) than with presence of at least 1 missense variant (17%; P < .01). Mean (SD) age at onset was higher for patients with at least 1 missense mutation (17.7 [11.4] vs 5.2 [2.6] years; P < .001).

Conclusions and Relevance

The AFP level, slightly elevated in a substantial fraction of patients, may constitute a new biomarker for AOA1. Oculomotor apraxia may be an optional finding in AOA1 and correlates with more severe disease. The p.Trp279* mutation is the most frequent APTX mutation in the white population. APTX missense mutations may be associated with a milder phenotype.

DEGS1 variant causes neurological disorder

Sphingolipidoses are monogenic lipid storage diseases caused by variants in enzymes of lipid synthesis and metabolism. We describe an autosomal recessive complex neurological disorder affecting consanguineous kindred. All four affected individuals, born at term following normal pregnancies, had mild to severe intellectual disability, spastic quadriplegia, scoliosis and epilepsy in most, with no dysmorphic features. Brain MRI findings were suggestive of leukodystrophy, with abnormal hyperintense signal in the periventricular perioccipital region and thinning of the body of corpus callosum. Notably, all affected individuals were asymptomatic at early infancy and developed normally until the age of 8-18 months, when deterioration ensued. Homozygosity mapping identified a single 8.7 Mb disease-associated locus on chromosome 1q41-1q42.13 between rs1511695 and rs537250 (two-point LOD score 2.1). Whole exome sequencing, validated through Sanger sequencing, identified within this locus a single disease-associated homozygous variant in DEGS1, encoding C4-dihydroceramide desaturase, an enzyme of the ceramide synthesis pathway. The missense variant, segregating within the family as expected for recessive heredity, affects an evolutionary-conserved amino acid of all isoforms of DEGS1 (c.656A>G, c.764A>G; p.(N219S), p.(N255S)) and was not found in a homozygous state in ExAC and gnomAD databases or in 300 ethnically matched individuals. Lipidomcs analysis of whole blood of affected individuals demonstrated augmented levels of dihydroceramides, dihydrosphingosine, dihydrosphingosine-1-phosphate and dihydrosphingomyelins with reduced levels of ceramide, sphingosine, sphingosine-1-phosphate and monohexosylceramides, as expected in malfunction of C4-dihydroceramide desaturase. Thus, we describe a sphingolipidosis causing a severe regressive neurological disease.

PIK3CA-associated developmental disorders exhibit distinct classes of mutations with variable expression and tissue distribution

Mosaicism is increasingly recognized as a cause of developmental disorders with the advent of next-generation sequencing (NGS). Mosaic mutations of PIK3CA have been associated with the widest spectrum of phenotypes associated with overgrowth and vascular malformations. We performed targeted NGS using 2 independent deep-coverage methods that utilize molecular inversion probes and amplicon sequencing in a cohort of 241 samples from 181 individuals with brain and/or body overgrowth. We identified PIK3CA mutations in 60 individuals. Several other individuals (n = 12) were identified separately to have mutations in PIK3CA by clinical targeted-panel testing (n = 6), whole-exome sequencing (n = 5), or Sanger sequencing (n = 1). Based on the clinical and molecular features, this cohort segregated into three distinct groups: (a) severe focal overgrowth due to low-level but highly activating (hotspot) mutations, (b) predominantly brain overgrowth and less severe somatic overgrowth due to less-activating mutations, and (c) intermediate phenotypes (capillary malformations with overgrowth) with intermediately activating mutations. Sixteen of 29 PIK3CA mutations were novel. We also identified constitutional PIK3CA mutations in 10 patients. Our molecular data, combined with review of the literature, show that PIK3CA-related overgrowth disorders comprise a discontinuous spectrum of disorders that correlate with the severity and distribution of mutations.

The clinical and molecular spectrum of PIK3CA-related developmental disorders are correlated with types of mutations, tissue distributions, and levels of mosaicism with the clinical phenotype.

A de novo GABRA2 missense mutation in severe early-onset epileptic encephalopathy with a choreiform movement disorder

BACKGROUND

Early-onset epileptic encephalopathy (EOEE) is a severe convulsive disorder with a poor developmental prognosis. Although it has been associated with mutations in a number of genes, the fact that there is a large proportion of patients who remain undiagnosed suggests that there are many more still-unknown genetic causes of EOEE. Achieving a genetic diagnosis is important for understanding the biological basis of the disease, with its implications for treatment and family planning.

METHODS

Whole-exome sequencing was performed in a family of Ashkenazi Jewish origin in which a male infant was diagnosed with EOEE. There was no family history of a similar neurologic disease. The patient had extreme hypotonia, neonatal hypothermia, choreiform movements, and vision impairment in addition to the convulsive disorder.

RESULTS

A de novo heterozygous missense mutation, c.1003A > C, p.Asn335His, was identified in a conserved domain of GABRA2. GABRA2 encodes the α2 subunit of the GABA_A receptor.

CONCLUSIONS

In the context of previous reports of an association of de novo mutations in genes encoding different subunits of the GABA_A receptor (GABRB1, GABRA1, GABRG2, GABRB3) with autosomal dominant epileptic disorders, we conclude that a de novo mutation in GABRA2 is likely to cause autosomal dominant EOEE accompanied by a movement disorder and vision impairment.

Novel RRM2B Mutation and Severe Mitochondrial DNA Depletion: Report of 2 Cases and Review of the Literature

Purpose To describe the clinical presentation and implications of mitochondrial DNA depletion disorder of two siblings with early fatal encephalomyopathy and a novel mutation in the RRM2B gene. The relevant literature is reviewed. Methods We describe two brothers aged 2.5 months and 1 month, respectively, who were hospitalized in a tertiary pediatric medical center for evaluation of focal seizures, hypotonia, poor feeding, failure to thrive, lactic acidosis, and developmental delay. The older brother also had seizures, and the younger had severe bilateral neurosensory deafness. Results Genetic sequencing of the RRM2B gene revealed the same novel mutation in both the siblings. Both children died due to respiratory failure at ages 3 and 2.5 months, respectively. Conclusion The combination of neonatal hypotonia, developmental delay, and lactic acidosis should raise a clinician's suspicion of a mitochondrial depletion disorder and prompt further genetic studies.

A homozygous PIGO mutation associated with severe infantile epileptic encephalopathy and corpus callosum hypoplasia, but normal alkaline phosphatase levels

We describe two sisters from a consanguineous Arab family with global developmental delay, dystrophy, axial hypotonia, epileptic encephalopathy dominated by intractable complex partial seizures that were resistant to various anti-epileptic treatments. Dysmorphic features comprised low set ears, hypertelorism, upslanting palpebral fissures, a broad nasal bridge, and blue sclera with elongated eyelashes. Brain MRI in both children showed a corpus callosum hypoplasia that was evident already in utero and evolving cortical atrophy. Autozygosity mapping in combination with Whole Exome Sequencing revealed a homozygous missense mutation in the PIGO gene [c.765G > A, NM_032634.3] that affected a highly conserved methionine in the alkaline phosphatase-like core domain of the protein [p.(Met255Ile), NP_116023.2]. PIGO encodes the GPI-ethanolamine phosphate transferase 3, which is crucial for the final synthetic step of the glycosylphosphatidylinositol-anchor that attaches many enzymes to their cell surfaces, such as the alkaline phosphatase and granulocyte surface markers. Interestingly, measurement of serum alkaline phosphatase activities in both children was normal or only slightly elevated. Quantification of granulocyte surface antigens CD16/24/59 yielded reduced levels only for CD59. Phenotype analysis of our and other published patients with PIGO mutations reveals a more severe affectation and predominantly neurological presentation in individuals carrying a mutation in the alkaline phosphatase-like core domain thereby hinting towards a genotype-phenotype relation for PIGO gene mutations.

Novel homozygous missense mutation in NT5C2 underlying hereditary spastic paraplegia SPG45

SPG45 is a rare form of autosomal recessive spastic paraplegia associated with mental retardation. Detailed phenotyping and mutation analysis was undertaken in three individuals with SPG45 from a consanguineous family of Arab Muslim origin. Using whole-exome sequencing, we identified a novel homozygous missense mutation in NT5C2 (c.1379T>C; p.Leu460Pro). Our data expand the molecular basis of SPG45, adding the first missense mutation to the current database of nonsense, frameshift, and splice site mutations. NT5C2 mutations seem to have a broad clinical spectrum and should be sought in patients manifesting either as uncomplicated or complicated HSP.

Myoclonus epilepsy and ataxia due to KCNC1 mutation: Analysis of 20 cases and K+ channel properties

OBJECTIVE

To comprehensively describe the new syndrome of myoclonus epilepsy and ataxia due to potassium channel mutation (MEAK), including cellular electrophysiological characterization of observed clinical improvement with fever.

METHODS

We analyzed clinical, electroclinical, and neuroimaging data for 20 patients with MEAK due to recurrent KCNC1 p.R320H mutation. In vitro electrophysiological studies were conducted using whole cell patch-clamp to explore biophysical properties of wild-type and mutant K_V 3.1 channels.

RESULTS

Symptoms began at between 3 and 15 years of age (median = 9.5), with progressively severe myoclonus and rare tonic-clonic seizures. Ataxia was present early, but quickly became overshadowed by myoclonus; 10 patients were wheelchair-bound by their late teenage years. Mild cognitive decline occurred in half. Early death was not observed. Electroencephalogram (EEG) showed generalized spike and polyspike wave discharges, with documented photosensitivity in most. Polygraphic EEG-electromyographic studies demonstrated a cortical origin for myoclonus and striking coactivation of agonist and antagonist muscles. Magnetic resonance imaging revealed symmetrical cerebellar atrophy, which appeared progressive, and a prominent corpus callosum. Unexpectedly, transient clinical improvement with fever was noted in 6 patients. To explore this, we performed high-temperature in vitro recordings. At elevated temperatures, there was a robust leftward shift in activation of wild-type K_V 3.1, increasing channel availability.

INTERPRETATION

MEAK has a relatively homogeneous presentation, resembling Unverricht-Lundborg disease, despite the genetic and biological basis being quite different. A remarkable improvement with fever may be explained by the temperature-dependent leftward shift in activation of wild-type K_V 3.1 subunit-containing channels, which would counter the loss of function observed for mutant channels, highlighting KCNC1 as a potential target for precision therapeutics. Ann Neurol 2017;81:677-689.

De novo GRIN1 mutations: An emerging cause of severe early infantile encephalopathy

De novo GRIN1 mutations have recently been shown to cause severe intellectual disability, hypotonia, hyperkinetic and stereotyped movements, and epilepsy. We report two new cases of severe early onset encephalopathy associated with hyperkinetic and oculogyric-like movements, caused by mutations in the GRIN1 gene; both were identified by whole exome sequencing. One of the patients harbored the novel mutation p.Ser688Tyr and the other patient harbored the p.Gly827Arg mutation, which was previously reported in three patients. In silico studies suggested that the p.Se688Tyr mutation results in disruption of NMDA ligand binding and the p.Gly827Arg mutation results in disrupted gating of the ion channel. Our study highlights the importance of GRIN1 mutations in the etiology of isolated cases of early onset encephalopathy, and the valuable role of whole exome sequencing in identifying these mutations.