Our knowledge of disease genes in neurological disorders is incomplete. With the aim of closing this gap, we performed whole-exome sequencing on 143 multiplex consanguineous families in whom known ...disease genes had been excluded by autozygosity mapping and candidate gene analysis. This prescreening step led to the identification of 69 recessive genes not previously associated with disease, of which 33 are here described (SPDL1, TUBA3E, INO80, NID1, TSEN15, DMBX1, CLHC1, C12orf4, WDR93, ST7, MATN4, SEC24D, PCDHB4, PTPN23, TAF6, TBCK, FAM177A1, KIAA1109, MTSS1L, XIRP1, KCTD3, CHAF1B, ARV1, ISCA2, PTRH2, GEMIN4, MYOCD, PDPR, DPH1, NUP107, TMEM92, EPB41L4A, and FAM120AOS). We also encountered instances in which the phenotype departed significantly from the established clinical presentation of a known disease gene. Overall, a likely causal mutation was identified in >73% of our cases. This study contributes to the global effort toward a full compendium of disease genes affecting brain function.
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•Multiplex consanguineous families are rich sources for novel gene discovery•Prescreening these families for known disease genes accelerates gene discovery•33 novel candidate genes are reported in this study
Using whole-exome sequencing on prescreened multiplex consanguineous families, Alazami et al. describe the identification of 33 novel candidate genes for various neurogenetic conditions. Such families are rich sources for novel gene discovery.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Mutations in PLA2G6 gene have variable phenotypic outcome including infantile neuroaxonal dystrophy, atypical neuroaxonal dystrophy, idiopathic neurodegeneration with brain iron accumulation and ...Karak syndrome. The cause of this phenotypic variation is so far unknown which impairs both genetic diagnosis and appropriate family counseling. We report detailed clinical, electrophysiological, neuroimaging, histologic, biochemical and genetic characterization of 11 patients, from 6 consanguineous families, who were followed for a period of up to 17 years. Cerebellar atrophy was constant and the earliest feature of the disease preceding brain iron accumulation, leading to the provisional diagnosis of a recessive progressive ataxia in these patients. Ultrastructural characterization of patients' muscle biopsies revealed focal accumulation of granular and membranous material possibly resulting from defective membrane homeostasis caused by disrupted PLA2G6 function. Enzyme studies in one of these muscle biopsies provided evidence for a relatively low mitochondrial content, which is compatible with the structural mitochondrial alterations seen by electron microscopy. Genetic characterization of 11 patients led to the identification of six underlying PLA2G6 gene mutations, five of which are novel. Importantly, by combining clinical and genetic data we have observed that while the phenotype of neurodegeneration associated with PLA2G6 mutations is variable in this cohort of patients belonging to the same ethnic background, it is partially influenced by the genotype, considering the age at onset and the functional disability criteria. Molecular testing for PLA2G6 mutations is, therefore, indicated in childhood-onset ataxia syndromes, if neuroimaging shows cerebellar atrophy with or without evidence of iron accumulation.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Klippel-Feil anomaly (KFA) can be seen in a number of syndromes. We describe an apparently novel syndromic association with KFA.
Clinical phenotyping of two consanguineous families followed by ...combined autozygome/exome analysis.
Two patients from two apparently unrelated families shared a strikingly similar phenotype characterised by KFA, myopathy, mild short stature, microcephaly, and distinctive facies. They shared a single founder autozygous interval in which whole exome sequencing revealed a truncating mutation in MYO18B. There was virtually complete loss of the transcript in peripheral blood, indicative of nonsense-mediated decay. Electron microscopy of muscle confirms abnormal myosin filaments with accompanying myopathic changes.
Deficiency of MYO18B is linked to a novel developmental disorder which combines KFA with myopathy. This suggests a widespread developmental role for this gene in humans, as observed for its murine ortholog.
Epileptic encephalopathy is a broad clinical category that is highly heterogeneous genetically.
To describe a multiplex extended consanguineous family that defines a molecularly novel subtype of ...early infantile epileptic encephalopathy.
Autozygosity mapping and exome sequencing for the identification of the causal mutation. This was followed by expression analysis of the candidate gene.
In an extended multigenerational family with six affected individuals, a single novel disease locus was identified on chromosome 12p13.31-p13.2. Within that locus, the only deleterious novel exomic variant was a homozygous truncating mutation in NECAP1, encoding a clathrin-accessory protein. The mutation was confirmed to trigger nonsense-mediated decay. Consistent with previous reports, we show that NECAP1 is highly enriched in the central nervous system.
NECAP1 is known to regulate clathrin-mediated endocytosis in synapses. The mutation we report here links for the first time this trafficking pathway in early infantile epileptic encephalopathy.
Brown-Vialetto-Van Laere (BVVL) syndrome is an extremely rare autosomal recessive progressive motoneuron disease that is caused by a defect in the riboflavin transporter genes SLC52A2 and SLC52A3. ...BVVL syndrome has a variable age of presentation, and it is characterized by progressive auditory neuropathy, bulbar palsy, stridor, muscle weakness, and respiratory compromise secondary to diaphragmatic and vocal cord paralysis. BVVL syndrome has a poor prognosis in the absence of treatment, including morbidity with quadriparesis and sensorineural hearing loss, with mortality in the younger age group. Early administration of riboflavin is associated with prolonged survival, low morbidity, and reversal of some clinical manifestations.
We describe an 18-month-old male infant with progressive pontobulbar palsy, loss of developmental milestones, and a clinical picture suggestive of chronic inflammatory demyelinating neuropathy. A nerve conduction study revealed axonal neuropathy, while molecular analysis revealed a homozygous mutation in one of the riboflavin transporter genes, SLC52A3, confirming BVVL syndrome. The patient needed long-term respiratory support and a gastrostomy tube to support feeding. With high-dose riboflavin supplementation, he experienced moderate recovery of motor function.
This report highlights the importance of considering BVVL syndrome in any patient who presents with the clinical phenotype of pontobulbar palsy and peripheral axonal neuropathy, as early riboflavin treatment may improve or halt disease progression, thus reducing the associated mortality and morbidity.
To evaluate the electro-clinical manifestations and outcomes of children with absence epilepsy at a tertiary center in Saudi Arabia.
This retrospective study reviewed the medical and EEG records of ...patients who were diagnosed to have CAE as per the International League Against Epilepsy (ILAE) definition for CAE. The study was conducted in the pediatric neurology clinic of King Khalid University Hospital, King Saud University Medical City, Riyadh, Saudi Arabia, between January 2000 and December 2019. Patients who did not meet (ILAE) criteria, lost follow-up, and those who did not receive treatment at KKUH were excluded. Data regarding the patient's disease, electro-clinical manifestations, anti-seizure medication response, and outcomes were collected.
A total of 35 patients, with an average age at diagnosis of 7 ± 2.1 y, were included in the study; among them, 51.4% were female and approximately 48.6% presented with a family history of epilepsy. Regarding clinical features, all patients experienced staring and altered awareness, 94.2% had less than 20 spells per day at the time of diagnosis, and 65.7% were provoked by the hyperventilation test. Regarding EEG findings, all patients had bilateral, symmetrical, and synchronous discharges in the form of regular 3 Hz spike-and-wave complexes, and 94.3% had a generalized initial ictal discharge. Also, 22.8% had eye fluttering with electrographic seizures. Ethosuximide (ESM) was used as the drug of choice in 45.7% of the patients. Regarding clinical outcomes, 94.3% had their disease clinically controlled, and 80% had a normalized EEG after few months of starting anti-seizure medication. Finally, 37.2% experienced complete remission of epilepsy after 3–5 y; however, one patient developed juvenile myoclonic epilepsy.
This study described the electro-clinical manifestations of patients with childhood absence epilepsy and outcomes. Furthermore, early diagnosis and prompt treatment of childhood absence epilepsy improve treatment outcomes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Abstract A significant etiological factor for upper respiratory tract infections and community-acquired pneumonia is Mycoplasma pneumoniae. The incidence of extrapulmonary neurological problems in ...infected patients has been shown to range from 0.1 to 7%, often manifesting within a timeframe of 2 to 14 days following the onset of respiratory symptoms. Acute disseminated encephalomyelitis, Guillain–Barré syndrome, and transverse myelitis are among the immune-mediated illnesses encompassed under the syndrome. A 3-year-old male child exhibited symptoms of acute encephalopathy and behavioral disruption subsequent to an infection caused by M. pneumoniae. He presented with irritability, sleep disturbance, slurred speech, increased appetite, episodes of unresponsiveness, moving in circles, staring, and laughing episodes lasting for up to 15 to 30 minutes over a week. He lost his previous toilet training. Abnormal jerks were noted while awake and asleep. Symptoms were preceded by exposure to vague febrile illness 3 weeks prior to presentation. The patient's brain magnetic resonance imaging was normal. Electroencephalography showed a slow background with no epileptiform discharges. Cerebrospinal fluid analysis and polymerase chain reaction for viruses were negative. The workup for autoimmune encephalitis was negative. Mycoplasma serology IgM was detected. Marked improvement was noted after methylprednisolone pulse therapy, intravenous immunoglobulin, valproic acid, and azithromycin. In conclusion, our report serves as a reminder that M. pneumoniae infection is a possible cause of encephalopathy and behavioral disturbance in children. Early recognition and promotion of immunomodulatory and antimicrobial treatment can prevent the affected child from experiencing different levels of long-lasting impairments in cognitive, physical, or visual abilities.
Background:
Acute necrotizing encephalopathy of childhood (ANEC) is a rapidly progressing encephalopathy characterized by fever, depressed level of consciousness, and seizures. Diagnosis depends on ...clinical presentation and characteristic neuroimaging findings of abnormal signal intensity involving the thalami as well as the supra and infra-tentorial areas. Treatment modalities are not well-established; empirical treatment with antibiotics and antiviral agents is the initial step, followed by steroids and immunoglobulin, as well as supportive care. Patients with ANEC have a variable prognosis, but mortality is very high.
Methods:
A retrospective chart review of patients diagnosed with ANEC in five tertiary centers from January 2015 to October 2018 was performed. Clinical and radiological findings, as well as the therapeutic approach and outcomes, were described.
Results:
Twelve children were included ranging in age from 10 months to 6 years. All patients presented with preceding febrile illness, altered level of consciousness, and seizure. Radiological features showed abnormal signals in the thalami, and five patients (41.7%) had brainstem involvement. All patients received empirical treatment with antibiotics and antiviral agents. Ten patients (83.3%) received intravenous immunoglobulin (IVIG) and IV Methylprednisolone therapy. Outcomes were variable ranging from good outcomes with minimal neurological deficits to poor outcomes and death in 25% of cases.
Conclusion:
ANEC is a rare fulminant disease in children. The treatment is challenging. Early interventions with the use of IVIG and IV Methylprednisolone may change the outcome; however, further studies are needed to establish a consensus guideline for the management.
To investigate seizure characteristics, types, and define the etiology of epilepsy in children aged ≤2 years using the 2017 ILAE classification.
A retrospective chart review was conducted at King ...Khalid University Hospital, King Saud University Medical City, Riyadh, Kingdom of Saudi Arabia for children below 2 years of age diagnosed with epilepsy, and on anti-seizure medications from January 2017 - December 2018. The collected data involved detailed information on the patients' seizure, electroclinical, neuroimaging, laboratory evaluations, and underlying etiology.
One- hundred and fifty patients were included in the study and classified according to etiology into: genetic (43, 28.7%), structural (41, 27.3%), metabolic (10, 6.7%), infectious (8, 5.3%), immune-mediated (1, 0.7%) and unknown (47, 31.3%) groups. The most common seizure types were generalized epilepsy, among which generalized tonic-clonic seizures occurred in 56 (37%) patients, followed by tonic seizures in 31 (21%), infantile spasm in 19 (13%), myoclonic seizures in 4 (2.7%), atonic seizures in 6 (4%), and focal seizures in 33 (22%) patients. Global developmental delay and abnormalities in both neurologic exam and neuroimaging were more common in the structural and genetic groups. Electroencephalography was abnormal in 82 (55%) patients, including the majority of the structural group (26, 63.4%).
The etiology of epilepsy in this cohort remains undetermined (unknown) in a large proportion of cases, followed by genetic and structural causes. This result added to the published international data about epilepsy in the first 2-years of life.
Molecular karyotyping has rapidly become the test of choice in patients with neurocognitive phenotypes, but studies of its clinical utility have largely been limited to outbred populations. In ...consanguineous populations, single-gene recessive causes of neurocognitive phenotypes are expected to account for a relatively high percentage of cases, thus diminishing the yield of molecular karyotyping. The aim of this study was to test the clinical yield of molecular karyotyping in the highly consanguineous population of Saudi Arabia.
We have reviewed the data of 584 patients with neurocognitive phenotypes (mainly referred from pediatric neurology clinics), all evaluated by a single clinical geneticist.
At least 21% of tested cases had chromosomal aberrations that are likely disease-causing. These changes include both known and novel deletion syndromes. The higher yield of molecular karyotyping in this study as compared with the commonly cited 11% can be explained by our ability to efficiently identify single-gene disorders, thus enriching the samples that underwent molecular karyotyping for de novo chromosomal aberrations. We show that we were able to identify a causal mutation in 37% of cases on a clinical basis with the help of autozygome analysis, thus bypassing the need for molecular karyotyping.
Our study confirms the clinical utility of molecular karyotyping even in highly consanguineous populations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
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