Diagnostic yield of chromosomal microarray and trio whole exome sequencing in cryptogenic cerebral palsy.

OBJECTIVE: To determine the yield of genetic diagnoses using chromosomal microarray (CMA) and trio whole exome sequencing (WES), separately and combined, among patients with cryptogenic cerebral palsy (CP). METHODS: Trio WES of patients with prior CMA analysis for cryptogenic CP, defined as disabling, non-progressive motor symptoms beginning before the age of 3 years without known cause. RESULTS: Given both CMA analysis and trio WES, clinically significant genetic findings were identified for 58% of patients (26 of 45). Diagnoses were eight large CNVs detected by CMA and 18 point mutations detected by trio WES. None had more than one severe mutation. Approximately half of events (14 of 26) were de novo. Yield was significantly higher in patients with CP with comorbidities (69%, 22 of 32) than in those with pure motor CP (31%, 4 of 13; p=0.02). Among patients with genetic diagnoses, CNVs were more frequent than point mutations among patients with congenital anomalies (OR 7.8, 95% CI 1.2 to 52.4) or major dysmorphic features (OR 10.5, 95% CI 1.4 to 73.7). Clinically significant mutations were identified in 18 different genes: 14 with known involvement in CP-related disorders and 4 responsible for other neurodevelopmental conditions. Three possible new candidate genes for CP were ARGEF10, RTF1 and TAOK3. CONCLUSIONS: Cryptogenic CP is genetically highly heterogeneous. Genomic analysis has a high yield and is warranted in all these patients. Trio WES has higher yield than CMA, except in patients with congenital anomalies or major dysmorphic features, but these methods are complementary. Patients with negative results with one approach should also be tested by the other.

Expanding the ß-III Spectrin-Associated Phenotypes toward Non-Progressive Congenital Ataxias with Neurodegeneration.

(1) Background: A non-progressive congenital ataxia (NPCA) phenotype caused by ß-III spectrin (SPTBN2) mutations has emerged, mimicking spinocerebellar ataxia, autosomal recessive type 14 (SCAR14). The pattern of inheritance, however, resembles that of autosomal dominant classical spinocerebellar ataxia type 5 (SCA5). (2) Methods: In-depth phenotyping of two boys studied by a customized gene panel. Candidate variants were sought by structural modeling and protein expression. An extensive review of the literature was conducted in order to better characterize the SPTBN2-associated NPCA. (3) Results: Patients exhibited an NPCA with hypotonia, developmental delay, cerebellar syndrome, and cognitive deficits. Both probands presented with progressive global cerebellar volume loss in consecutive cerebral magnetic resonance imaging studies, characterized by decreasing midsagittal vermis relative diameter measurements. Cortical hyperintensities were observed on fluid-attenuated inversion recovery (FLAIR) images, suggesting a neurodegenerative process. Each patient carried a novel de novo SPTBN2 substitution: c.193A > G (p.K65E) or c.764A > G (p.D255G). Modeling and protein expression revealed that both mutations might be deleterious. (4) Conclusions: The reported findings contribute to a better understanding of the SPTBN2-associated phenotype. The mutations may preclude proper structural organization of the actin spectrin-based membrane skeleton, which, in turn, is responsible for the underlying disease mechanism.

Expanding the phenotype of IBA57 mutations: related leukodystrophy can remain asymptomatic.

Biallelic mutations in IBA57 cause a mitochondrial disorder with a broad phenotypic spectrum that ranges from severe intellectual disability to adolescent-onset spastic paraplegia. Only 21 IBA57 mutations have been reported, therefore the phenotypic spectrum of IBA57-related mitochondrial disease has not yet been fully elucidated. In this study, we performed whole-exome sequencing on a Sepharadi Jewish and Japanese family with leukodystrophy. We identified four novel biallelic variants in IBA57 in the two families: one frameshift insertion and three missense variants. The three missense variants were predicted to be disease-causing by multiple in silico tools. The 29-year-old Sepharadi Jewish male had infantile-onset optic atrophy with clinically asymptomatic leukodystrophy involving periventricular white matter. The 19-year-old younger brother, with the same compound heterozygous IBA57 variants, had a similar clinical course until 7 years of age. However, he then developed a rapidly progressive spastic paraparesis following a febrile illness. A 7-year-old Japanese girl had developmental regression, spastic quadriplegia, and abnormal periventricular white matter signal on brain magnetic resonance imaging performed at 8 months of age. She had febrile convulsions at the age of 18 months and later developed epilepsy. In summary, we have identified four novel IBA57 mutations in two unrelated families. Consequently, we describe a patient with infantile-onset optic atrophy and asymptomatic white matter involvement, thus broadening the phenotypic spectrum of biallelic IBA57 mutations.

Hypomyelination with atrophy of the basal ganglia and cerebellum: further delineation of the phenotype and genotype-phenotype correlation.

Hypomyelination with atrophy of the basal ganglia and cerebellum is a rare leukoencephalopathy that was identified using magnetic resonance imaging in 2002. In 2013, whole exome sequencing of 11 patients with the disease revealed that they all had the same de novo mutation in TUBB4A, which encodes tubulin ß-4A. We investigated the mutation spectrum in a cohort of 42 patients and the relationship between genotype and phenotype. Patients were selected on the basis of clinical and magnetic resonance imaging abnormalities that are indicative of hypomyelination with atrophy of the basal ganglia and cerebellum. Genetic testing and a clinical inventory were performed, and sequential magnetic resonance images were evaluated using a standard protocol. The heterozygous TUBB4A mutation observed in the first 11 patients was the most common (25 patients). Additionally, 13 other heterozygous mutations were identified, located in different structural domains of tubulin ß-4A. We confirmed that the mutations were de novo in all but three patients. In two of these three cases we lacked parental DNA and in one the mutation was also found in the mother, most likely due to mosaicism. Patients showed a phenotypic continuum ranging from neonatal to childhood disease onset, normal to delayed early development and slow to more rapid neurological deterioration. Neurological symptomatology consisted of extrapyramidal movement abnormalities, spasticity, ataxia, cognitive deficit and sometimes epilepsy. Three patients died and the oldest living patient was 29 years of age. The patients' magnetic resonance images showed an absent or disappearing putamen, variable cerebellar atrophy and highly variable cerebral atrophy. Apart from hypomyelination, myelin loss was evident in several cases. Three severely affected patients had similar, somewhat atypical magnetic resonance image abnormalities. The study results were strongly suggestive of a genotype-phenotype correlation. The 25 patients with the common c.745G>A mutation generally had a less rapidly progressive disease course than the 17 cases with other TUBB4A mutations. Overall, this work demonstrates that the distinctive magnetic resonance imaging pattern for hypomyelination with atrophy of the basal ganglia and cerebellum defines a homogeneous clinical phenotype of variable severity. Patients almost invariably have prominent extrapyramidal movement abnormalities, which are rarely seen in patients with hypomyelination of different origin. A dominant TUBB4A mutation is also associated with dystonia type 4, in which magnetic resonance images of the brain seem normal. It is highly likely that there is a disease continuum associated with TUBB4A mutations, of which hypomyelination with atrophy of the basal ganglia and cerebellum and dystonia type 4 are the extremes. This would indicate that extrapyramidal movement abnormalities constitute the core feature of the disease spectrum related to dominant TUBB4A mutations and that all other features are variable.

Progressive cerebello-cerebral atrophy and progressive encephalopathy with edema, hypsarrhythmia and optic atrophy may be allelic syndromes.

In 2003, a new syndrome was described in the Sephardi Jewish population, named progressive cerebello-cerebral atrophy (PCCA) based on the typical neuroradiological findings. Following the identification of the causal genes in 2010 and 2014, two types were defined: PCCA type 1 due to SEPSECS mutations and PCCA type 2 due to VPS53 mutations. Progressive encephalopathy with edema, hypsarrhythmia and optic atrophy (PEHO) was described in 1991 in Finland. The clinical and radiological phenotype resembles PCCA. The genetic background has been elusive for many years. Recently, mutations in multiple genes including SEPSECS have been described in patients with a PEHO-like syndrome. In 2007 two siblings of Moroccan-Jewish origin were diagnosed as having PEHO due to a severe developmental encephalopathy, limb and facial edema, intractable epilepsy, optic atrophy in one sibling and dysmorphic features. Six years ago an extensive workup, including whole exome sequencing, did not reveal the cause. Recently, a clinical reevaluation of the siblings suggested the possibility that they suffer from PCCA. A reanalysis of the exome data from 2014 revealed that the siblings indeed carried the two VPS53 mutations (exon 19 c.2084A>G p.(Gln695Arg) and c.1556 + 5G>A) and the parents were found to be carriers. The discovery that mutations in both VPS53 and SEPSECS can present with a PEHO-like phenotype, place PCCA and PEHO on the same clinical spectrum and suggest they may be allelic syndromes.

Copy number variations in cryptogenic cerebral palsy.

OBJECTIVE: To determine the prevalence and characteristics of copy number variations (CNVs) in children with cerebral palsy (CP) of unknown etiology, comprising approximately 20% of the CP population. METHODS: Fifty-two participants (age 10.5 ± 7.8 years; Gross Motor Function Classification System scale 2.8 ± 1.3) with nonprogressive pyramidal and/or extrapyramidal signs since infancy and no identified etiology were enrolled. Individuals with evidence of acquired causes were excluded. Participants underwent neurologic and clinical genetic examinations before the genomic testing. Chromosomal microarray analysis to detect CNVs was performed using the Affymetrix platform. CNVs identified were classified as pathogenic, likely pathogenic, likely benign, or benign. Only pathogenic and likely pathogenic CNVs were defined as clinically significant. RESULTS: Thirty-nine CNVs were found in 25 of 52 participants (48%). Sixteen participants (31%) had clinically significant CNVs: 10 pathogenic and 6 likely pathogenic, of which 7 were not previously associated with motor disability. Nine participants had likely benign CNVs. Clinically significant CNVs were more frequently de novo (12/16; p < 0.001) including in 5 of 8 individuals who had a first- or second-degree relative with a major neurologic disorder. Dysmorphic features and nonmotor comorbidities were more prevalent in individuals with clinically significant CNVs (p < 0.05 for both). CONCLUSION: CNVs, most frequently de novo, are common in individuals with cryptogenic CP. We recommend CNV testing in individuals with CP of unknown etiology.

De novo mutations in KIF1A cause progressive encephalopathy and brain atrophy.

OBJECTIVE: To determine the cause and course of a novel syndrome with progressive encephalopathy and brain atrophy in children. METHODS: Clinical whole-exome sequencing was performed for global developmental delay and intellectual disability; some patients also had spastic paraparesis and evidence of clinical regression. Six patients were identified with de novo missense mutations in the kinesin gene KIF1A. The predicted functional disruption of these mutations was assessed in silico to compare the calculated conformational flexibility and estimated efficiency of ATP binding to kinesin motor domains of wild-type (WT) versus mutant alleles. Additionally, an in vitro microtubule gliding assay was performed to assess the effects of de novo dominant, inherited recessive, and polymorphic variants on KIF1A motor function. RESULTS: All six subjects had severe developmental delay, hypotonia, and varying degrees of hyperreflexia and spastic paraparesis. Microcephaly, cortical visual impairment, optic neuropathy, peripheral neuropathy, ataxia, epilepsy, and movement disorders were also observed. All six patients had a degenerative neurologic course with progressive cerebral and cerebellar atrophy seen on sequential magnetic resonance imaging scans. Computational modeling of mutant protein structures when compared to WT kinesin showed substantial differences in conformational flexibility and ATP-binding efficiency. The de novo KIF1A mutants were nonmotile in the microtubule gliding assay. INTERPRETATION: De novo mutations in KIF1A cause a degenerative neurologic syndrome with brain atrophy. Computational and in vitro assays differentiate the severity of dominant de novo heterozygous versus inherited recessive KIF1A mutations. The profound effect de novo mutations have on axonal transport is likely related to the cause of progressive neurologic impairment in these patients.

[Ketogenic diet as antiepileptic therapy: a description of the clinical experience and the multidisciplinary approach at the metabolic-neurogenetic clinic at the Wolfson Medical Center].

UNLABELLED: The ketogenic diet, built on a menu that includes a high fat content and low protein and carbohydrate percentages, constitutes an alternative therapy for children with refractory epilepsy. This study describes our clinical experience with the diet, its efficacy, and the adverse effects associated with this treatment modality, which is mainly indicated in patients who do not respond to conventional antiepileptic drugs (AEDs). We place particular emphasis on our multidisciplinary approach, which includes physicians, nurses, social workers, and dieticians. A chart review was performed on all pediatric patients who received the diet in our clinic between 1998 and 2003. We recorded the patients' demographic data, the age at epilepsy onset, the age of the patient at the time the diet was started, the characteristics of the epilepsy, the seizure frequency, the AEDs prior to and during the diet, the patient and family compliance, and the adverse effects. RESULTS: Ten patients were treated. The youngest patient was 8 months old and the oldest was 19 years old at the onset of the diet. Eight children suffered from a well-defined epileptic syndrome. All children had frequent seizures and received between 2 and 9 AEDs prior to the diet. The duration of the diet ranged between 6 weeks and two and a half years. Seven patients experienced over 50% seizure reduction while on the diet. However, total seizure control was not attained in any patient. Adverse effects were minimal. All the patients complied with this rigid diet in a good or excellent manner. Furthermore, we also observed an improvement in the degree of alertness, learning skills, and developmental milestones in most of the children. The diet failed to provide satisfactory seizure control or improvement in the well-being of 3 patients. In conclusion, the ketogenic diet is an effective therapeutic alternative for children with refractory epilepsy, irrespective of the patient's age, gender or disease duration. We attribute our therapeutic success with the diet to the multidisciplinary approach carried out in our clinic.