Early clinical features and diagnosis of Dravet syndrome in 138 Chinese patients with SCN1A mutations

Objective: To summarize the early clinical features of Dravet syndrome (DS) patients with SCN1A gene mutations before the age of one. Methods: SCN1A gene mutation screening was performed by PCR–DNA sequencing and multiple ligation-dependent probe amplication (MLPA). The early clinical features of DS patients with SCN1A mutations were reviewed with attention to the seizures induced by fever and other precipitating factors before the first year of life. Results: The clinical data of 138 DS patients with SCN1A gene mutations were reviewed. The median seizure onset age was 5.3 months. Ninety-nine patients (71.7%) experienced seizures with duration more than 15 min in the first year of life. Two or more seizures induced by fever within 24 h or the same febrile illness were observed in 93 patients (67.4%). 111 patients (80.4%) had hemi-clonic and (or) focal seizures. Seizures had been triggered by fever of low degree (T < 38 °C) in 62.3% (86/138) before the first year of life. Vaccine-related seizures were observed in 34.8% (48/138). Seizures in 22.5% (31/138) of patients were triggered by hot bath. Carbamazepine, oxcarbazepine, lamotrigine, phenobarbital and phenytoin showed either no effect or exacerbating the seizures in our group. Conclusion: The seizure onset age in DS patients was earlier than that was in common febrile seizures. When a baby exhibits two or more features of complex febrile seizures in the first year of life, a diagnosis of DS should be considered, and SCN1A gene mutation screening should be performed as early as possible. Early diagnosis of DS will help clinicians more effectively prescribe antiepileptic drugs for stronger prognosis.     

A homozygous mutation of voltage‐gated sodium channel βI gene SCN1B in a patient with Dravet syndrome

Dravet syndrome is a severe form of epileptic encephalopathy characterized by early onset epileptic seizures followed by ataxia and cognitive decline. Approximately 80% of patients with Dravet syndrome have been associated with heterozygous mutations in SCN1A gene encoding voltage‐gated sodium channel (VGSC) α_I subunit, whereas a homozygous mutation (p.Arg125Cys) of SCN1B gene encoding VGSC β_I subunit was recently described in a patient with Dravet syndrome. To further examine the involvement of homozygous SCN1B mutations in the etiology of Dravet syndrome, we performed mutational analyses on SCN1B in 286 patients with epileptic disorders, including 67 patients with Dravet syndrome who have been negative for SCN1A and SCN2A mutations. In the cohort, we found one additional homozygous mutation (p.Ile106Phe) in a patient with Dravet syndrome. The identified homozygous SCN1B mutations indicate that SCN1B is an etiologic candidate underlying Dravet syndrome.     

A case of SUDEP in a patient with Dravet syndrome with SCN1A mutation

A boy with a clinical history of pharmacologically resistant Dravet syndrome died suddenly after falling asleep. The autopsy concluded that the cause of death was sudden unexpected death in epilepsy (SUDEP). Postmortem molecular analysis of the SCN1A gene by multiplex ligation‐dependent probe amplification (MLPA), high‐resolution melting curve analysis (HRMCA), and sequencing revealed a frameshift duplication of adenosine at position 504. The incidence of this mutation is discussed as a potential cause of SUDEP.     

Dravet syndrome or genetic (generalized) epilepsy with febrile seizures plus?

Dravet syndrome and genetic epilepsy with febrile seizures plus (GEFS+) can both arise due to mutations of SCN1A, the gene encoding the alpha 1 pore-forming subunit of the sodium channel. GEFS+ refers to a familial epilepsy syndrome where at least two family members have phenotypes that fit within the GEFS+ spectrum. The GEFS+ spectrum comprises a range of mild to severe phenotypes varying from classical febrile seizures to Dravet syndrome. Dravet syndrome is a severe infantile onset epilepsy syndrome with multiple seizure types, developmental slowing and poor outcome. More than 70% of patients with Dravet syndrome have mutations of SCN1A; these include both truncation and missense mutations. In contrast, only 10% of GEFS+ families have SCN1A mutations and these comprise missense mutations. GEFS+ has also been associated with mutations of genes encoding the sodium channel beta 1 subunit, SCN1B, and the GABA_A receptor gamma 2 subunit, GABRG2. The phenotypic heterogeneity that is characteristic of GEFS+ families is likely to be due to modifier genes. Interpretation of the significance of a SCN1A missense mutation requires a thorough understanding of the phenotypes in the GEFS+ spectrum whereas a de novo truncation mutation is likely to be associated with a severe phenotype. Early recognition of Dravet syndrome is important as aggressive control of seizures may improve developmental outcome.     

On the likelihood of SCN1A microdeletions or duplications in Dravet syndrome with missense mutation

This study examines whether microdeletions and duplications of the gene encoding α1 subunit of the sodium channel (SCN1A) are underlying causes in Dravet syndrome (DS) with SCN1A missense mutation. Multiple exonic deletions were identified in 8/84 patients without mutation and 0/41 patients with missense mutations. Our findings indicate that while microdeletions are not rare in SCN1A-negative patients, they are not likely to be present simultaneously with other SCN1A mutations.     

A screening test for the prediction of Dravet syndrome before one year of age

PURPOSE: Our aim was to develop a screening test to predict Dravet syndrome before the first birthday based on the clinical characteristics of infants and the SCN1A mutation analysis. METHODS: Ninety-six patients who experienced febrile seizures before the age of one were enrolled. The patients were divided into two groups-the Dravet syndrome group (n = 46) and the non-Dravet syndrome group (n = 50). We compared the clinical characteristics before one year of age of the two groups. We analyzed all coding exons of the SCN1A gene by the direct sequencing method. Scores from 0 to 3 were assigned to each risk factor based on the odds ratio and p-value. RESULTS: An age of onset of febrile seizure or= 5, and prolonged seizures lasting more than 10 min. were regarded as significant risk factors for Dravet syndrome. Other factors highly predictive of this syndrome were hemiconvulsions, partial seizures, myoclonic seizures, and hot water-induced seizures. A total clinical score of six or above was the cutoff value indicating a high risk of Dravet syndrome. SCN1A missense and truncated mutations were detected significantly more often in the Dravet syndrome group than in the non-Dravet syndrome group. DISCUSSION: This simple screening test was designed to be used by general pediatricians. It could help to predict Dravet syndrome before one year of age. If the sum of the clinical risk score is >or= 6, then the performance of an SCN1A mutation analysis is recommended.     

Somatic mosaicism for Y120X mutation in the MECP2 gene causes atypical Rett syndrome in a male

Rett Syndrome (RS; MIM_312750) is a severe and progressive neurodevelopmental disorder affecting principally females. Mutations in X-Linked MECP2 gene (methyl CpG-binding protein 2; MIM_300005) have been reported as being the major cause of RS. Mutations in this gene have been described as cause of wide spectrum of neurological disorders and mental retardation in males. In some cases, mutations in MECP2 in males produce clinical picture similar to RS.Here we report the identification of the novel truncating mutation Y120X in a 4-year-old child with atypical RS phenotype. Chromosome analysis showed a normal karyotype, and blood DNA and tissue DNA analysis reveal a mosaic for the mutation.Patient’s mother DNA analysis showed that this is a de novo mutation, that has never been described before in any female or male case of RS.     

Role of the sodium channel SCN9A in genetic epilepsy with febrile seizures plus and Dravet syndrome

Mutations of the SCN1A subunit of the sodium channel is a cause of genetic epilepsy with febrile seizures plus (GEFS⁺) in multiplex families and accounts for 70–80% of Dravet syndrome (DS). DS cases without SCN1A mutation inherited have predicted SCN9A susceptibility variants, which may contribute to complex inheritance for these unexplained cases of DS. Compared with controls, DS cases were significantly enriched for rare SCN9A genetic variants. None of the multiplex febrile seizure or GEFS⁺ families could be explained by highly penetrant SCN9A mutations.     

Lissencephaly with marked ventricular dilation,agenesis of corpus callosum,and cerebellar hypoplasia caused by TUBA1A mutation

We described the clinical course and pathological findings in a child with TUBA1A mutation. MRI revealed marked ventricular dilation with thin cortex, poorly differentiated basal ganglia, agenesis of corpus callosum, cerebellar hypoplasia with preserved vermis at 2 months of age. No gain of developmental milestones was observed until she died with respiratory failure at 23 months of age. A de novo missense mutation of c.1096G>A (G366R) was identified in TUBA1A gene. Pathological findings included a lack in lamination in the cerebral cortex, absent corpus callosum without Probst bundle, blurred demarcation among the striatum, internal capsule and globus pallidus in association with irregular running of myelinated fibers, cerebellar hypoplasia with irregular undulation in the dentate nucleus and inferior olivary nucleus, absent olfactory bulbs and tracts, and pyramidal tract hypoplasia. These findings are consistent with previous reports and will be a clue to diagnosis of TUBA1A mutation.     

Severe phenotypes of paralysis periodica paramyotonia are associated with the Met1592Val mutation in the voltage-gated sodium channel gene (SCN4A) in a Chinese family

Paralysis periodica paramyotonia (PPP) is caused by mutation of the adult skeletal muscle sodium channel gene’s alpha (??)-subunit (SCN4A). Here, we report four generations of a Chinese family affected by a remarkably severe form of PPP with progressive myopathy. Routine electromyograms (EMG) showed myotonic discharge and after a long exercise test, compound motor action potential amplitudes were markedly decreased by 40-55%. Muscle biopsy revealed obvious vacuolar changes. Moreover, genetic analysis revealed the Met1592Val mutation in the ??-subunit, SCN4A. The patients showed a striking clinical and electrophysiological improvement during treatment with acetazolamide. Thus, our findings showed that mutation of Met1592Val in the SCN4A gene is associated with aggressive development of PPP characterized by severe vacuolar myopathy.     

Comorbidities and predictors of health-related quality of life in Dravet syndrome

Purpose: Health‐related quality of life (HRQOL) has emerged as a widely accepted measure to evaluate how chronic disease impacts on an individual’s physical, social, and mental well‐being. There is a paucity of data focusing on HRQOL in specific epilepsy syndromes and their associated needs. In this study our aim was to describe the comorbidities and disease‐related predictors for HRQOL in Dravet syndrome, an epileptic encephalopathy, with defined genetic etiology. We anticipate that this will help us to better recognize and understand the needs of children and families and aid treatment planning in this severe epilepsy syndrome. Methods: One hundred sixty‐three individuals with Dravet syndrome and their families participated in the study. Detailed clinical and demographic information was available for each case. HRQOL was evaluated with two epilepsy‐specific instruments, the Impact of Pediatric Epilepsy Scale (IPES) and the Epilepsy & Learning Disabilities Quality of Life Questionnaire (ELDQOL); a generic HRQOL instrument; the Pediatric Quality of Life Inventory (PedsQL); and a behavioral screening tool, the Strength and Difficulties Questionnaire (SDQ). Key Findings: HRQOL was significantly lower for children with Dravet syndrome compared to normative data (p < 0.001). A cross‐sectional evaluation of measures across different age groups revealed that PedsQL generic core and cognitive function scales decreased in older age categories, indicating worse HRQOL (p < 0.001). Assessment of epilepsy severity demonstrated that symptoms were rated very severe in 10 (6%) of 162 cases, somewhat severe in 78 (48%) of 162, moderate in 51 (32%) of 162, and mild in 23 (14%) of 162 cases. The epilepsy severity correlated significantly with the IPES total impact score (r = 0.466, p < 0.001, n = 162). The IPES total impact scores in the Dravet group (n = 162) were significantly higher than scores measured in the original validation sample of epileptic children with and without learning difficulties (± SD) (21.0 ± 8.7 vs. 11.6 ± 5.4, t = 8.95, p < 0.001, n = 46). On the SDQ, 35% of children scored in the abnormal range for “conduct problems,” 66% for “hyperactivity/ inattention,” and 76% for “peer relationships.” Regression analysis revealed that young age at seizure onset (p = 0.019), presence of myoclonic seizures (p = 0.029), motor disorder (p = 0.048), learning difficulties (p = 0.002), epilepsy severity (p < 0.001), and behavioral difficulties (p < 0.001) each independently predicted poorer HRQOL. Behavioral problems such as hyperactivity/inattention were the strongest predictors of poorer HRQOL. Significance: This is the first comprehensive study of HRQOL in an etiologically well‐defined epilepsy syndrome. HRQOL in Dravet syndrome depends on a series of independent factors including seizure control, behavior, cognitive, and motor problems. Identification of specific comorbidities in Dravet syndrome will facilitate a distinct and multidisciplinary approach to management, addressing seizure control, behavior problems, cognitive difficulties, and motor impairment.     

Successful use of fenfluramine as an add-on treatment for Dravet syndrome

Purpose: Despite the development of new antiepileptic drugs, Dravet syndrome frequently remains therapy resistant and is a catastrophic epilepsy syndrome. Fenfluramine is an amphetamine‐like drug that has been used in the past as a part of antiobesity treatments. Because of the possible cardiac adverse effects (valve thickening, pulmonary hypertension) associated with use of fenfluramine, it was withdrawn from the market in 2001. In Belgium, a Royal Decree permitted examination of the potential anticonvulsive effects of fenfluramine in a clinical trial consisting of a small group of patients diagnosed with Dravet syndrome. Methods: Herein, we report 12 patients, 7 female and 5 male, with a genetically proven (11 of 12) diagnosis of Dravet syndrome who received fenfluramine as add‐on therapy. Key Findings: Their ages at their last evaluation ranged from 3–35 years. The mean dosage of fenfluramine was 0.34 (0.12–0.90) mg/kg/day. Exposure duration to fenfluramine ranged from 1–19 years. Seven of the patients who were still receiving the fenfluramine treatment at the time of the last visit had been seizure‐free for at least 1 year. In total, patients had been seizure‐free for a mean of 6 (1–19) years. In seven patients, the fenfluramine treatment was interrupted once during the follow‐up; seizures reappeared in three of the seizure‐free patients. Subsequent reintroduction of fenfluramine controlled the seizures in these three patients again. Only two patients exhibited a mild thickening of one or two cardiac valves without clinical significance. Significance: Compared with a recent long‐term follow‐up series in which a maximum of 16% of patients with Dravet syndrome were seizure‐free, our result of 70% of patients with Dravet syndrome remaining seizure‐free is noteworthy. Given the limitations of this observational study, a larger prospective study should be undertaken to confirm these promising results.     

Identification and characterization of novel sequence variations in MECP2 gene in Rett syndrome patients

Rett syndrome (RS) is a neurodevelopmental disorder caused by mutations in MECP2 gene. Exons 2, 3, and 4, in addition to intronic and 3′UTR adjacent regions, were sequenced in 80 patients with RS. Twenty-nine sequence variations were detected in 49 patients, 34 (69.4%) patients with the classic form of RS, and 15 (30.6%) patients with atypical forms of RS. Thirteen of the 29 detected mutations represent novel sequence variations. Missense mutation T158M was the most commonly observed mutation, detected in nine patients (11.2%). Six hotspot pathogenic mutations (R133C, T158M, R168X, R255X, R270X, and R294X) were responsible for the phenotype in 26/80 patients (32.5%).     

Five‐year extended follow‐up status of 10 patients with Dravet syndrome treated with fenfluramine

Dravet syndrome (DS) is a rare and therapy‐resistant epilepsy syndrome. A retrospective analysis of add‐on fenfluramine treatment in 12 patients with DS was published in 2012 and provided evidence of a meaningful long‐term response. Herein we present the results of a subsequent 5‐year prospective observation of this original cohort. Ten patients with a mean current age of 24 years were followed prospectively from 2010 until 2014. The mean current dose of fenfluramine was 0.27 mg/kg/day, with a mean treatment duration of 16.1 years. Seizure frequency was derived from a seizure diary. Cardiac examinations and assessments of clinical effectiveness and adverse events were performed at least annually. Three patients were seizure‐free for the entire 5 years, and an additional four patients experienced seizure‐free intervals of at least 2 years. Fenfluramine was generally well‐tolerated. Two patients had mild (stable) valve thickening on the last echocardiography that was deemed clinically insignificant. No patient had any clinical or echocardiographic signs of pulmonary hypertension. These findings support the long‐term control of convulsive seizures by low‐dose fenfluramine while being well tolerated in this cohort of patients with DS. After up to 27 years of treatment, no patient has developed any clinical signs or symptoms of cardiac valvulopathy or pulmonary hypertension.     

Molecular basis of severe myoclonic epilepsy in infancy

Severe myoclonic epilepsy (SMEI) or Dravet syndrome is caused by mutations of the SCN1A gene that encodes voltage-gated sodium channel alpha-1 subunit. Recently, we generated and characterized a knock-in (KI) mice with an SCN1A nonsense mutation that appeared in three independent SMEI patients. The SCN1A-KI mice well reproduced the SMEI disease phenotypes. Both homozygous and heterozygous knock-in mice developed epileptic seizures within the first postnatal month. In heterozygous knock-in mice, trains of evoked action potentials in inhibitory neurons exhibited pronounced spike amplitude decrement late in the burst but not in pyramidal neurons. We further showed that in wild-type mice the Nav1.1 protein is expressed dominantly in axons and moderately in somata of parbalbumin (PV) – positive inhibitory interneurons. Our immunohistochemical observations of the Nav1.1 are clearly distinct to the previous studies, and our findings has corrected the view of the Nav1.1 protein distribution. The data indicate that Nav1.1 plays critical roles in the spike output from PV interneurons and further, that the specifically altered function of these inhibitory circuits may contribute to epileptic seizures in the mice. These information should contribute to the understanding of molecular pathomechanism of SMEI and to develop its effective therapies.     

Clinical spectrum of SCN2A mutations

Mutations in SCN2A, the gene encoding α2 subunit of the neuronal sodium channel, are associated with a variety of epilepsies: benign familial neonatal-infantile seizures (BFNIS); genetic epilepsy with febrile seizures plus (GEFS+); Dravet syndrome (DS); and some intractable childhood epilepsies. More than 10 new mutations have been identified in BFNIS, all of them are missense. To date, only one nonsense mutation has been found in a patient with intractable childhood epilepsy and severe mental decline. Recently, microduplication of chromosome 2q24.3 (containing eight genes including SCN2A, SCN3A, and the 3' end of SCN1A) was reported in a family with dominantly inherited neonatal seizures and intellectual disability. Functional studies of SCN2A mutations show that they can cause divergent biophysical defects in Na(V)1.2 and impair cell surface expressions. There is no consistent relationship between genotype and phenotype.     

Mutations in the NKX2-5 gene in patients with stroke and patent foramen ovale

Objective

Patent foramen ovale (PFO) has been related to stroke but its existence has not been explained to date. NKX2-5 is the most implicated gene in fetal atrial septation. We studied NKX2-5 with respect to the presence or absence of PFO in stroke patients.

Methods

A prospective analysis of NKX2-5 regarding age, gender, PFO, right-to-left shunt (RLS) size and atrial septal aneurysm (ASA) was performed in consecutive stroke patients and in 50 controls. The entire coding region and intron–exon boundaries of NKX2-5 gene were analyzed by PCR and sequencing of DNA from peripheral lymphocytes.

Results

One hundred patients participated in the study (mean age 56.5 ± 12.4 years, 58% males) and PFO was diagnosed in 34% of them by transesophageal echocardiography. RLS was small (12%), moderate (2%) and large (20%). ASA was present in four patients. DNA revealed a novel c.2357G>A change in one PFO patient with cryptogenic stroke. Furthermore, c.182C>T, a mutation previously described in patients with cardiac defects, was detected in two non-PFO women with cryptogenic stroke. None of these changes were detected in our controls. The c.172A>G polymorphism was found in 21% of controls. It appeared more frequently in ASA patients (p = 0.084), in cryptogenic PFO stroke patients (p = 0.097) and in patients with known causes of stroke (p = 0.037). The c.2850C>A polymorphism was also detected in our series with no differences in PFO, RLS size or ASA.

Conclusion

Despite the fact that the NKX2-5 could account for the persistence of PFO, mutations of this gene in peripheral blood DNA were barely detected in our study.