Different experiences of two PRRT2-associated self-limited familial infantile epilepsy

Levetiracetam may be an unsuitable choice for patients with PRRT2-associated self-limited infantile epilepsy

INTRODUCTION

Self-limited infantile epilepsy (SeLIE) is a benign epilepsy. Previous studies have shown that monotherapy with most antiseizure medications can effectively relieve seizures in patients with SeLIE, but the efficacy of levetiracetam has not been investigated.

OBJECTIVE

This study aimed to investigate the efficacy of levetiracetam in the treatment of SeLIE patients with PRRT2 mutations.

METHODS

The clinical data of 39 SeLIE patients (21 males and 18 females, aged 4.79 ± 1.60 months) with pathogenic variants in PRRT2 or 16p11.2 microdeletion were retrospectively analyzed. Based on the use of initial antiseizure medication (ASM), the patients were classified into two groups: Levetiracetam group (LEG) and Other ASMs group (OAG). The difference of efficacy between the two groups was compared.

RESULTS

Among the 39 SeLIE patients, 16 were LEG (10 males and 6 females, aged 5.25 ± 2.07 months), with whom two obtained a seizure-free status (12.50%) and 14 ineffective or even deteriorated (87.50%). Among the 14 ineffective or deteriorated cases, 13 were seizure-controlled after replacing levetiracetam with other ASMs including topiramate, oxcarbazepine, lamotrigine, and valproate, and the remaining one finally achieved remission at age 3. Of the 39 patients, 23 were OAG (11 males and 12 females; aged 4.48 ± 1.12 months), of whom 22 achieved seizure remission, except for one patient who was ineffective with topiramate initially and relieved by oxcarbazepine instead. Although there were no significant differences in gender and age of onset between the two groups, the effective rate was significantly different (12.50% in LEG vs. 95.65% in OAG) (P < 0.01).

CONCLUSION

The findings showed that patients with SeLIE caused by the PRRT2 mutations did not benefit from the use of levetiracetam, but could benefit from other ASMs.

Clinical and genetic analysis of benign familial infantile epilepsy caused by PRRT2 gene variant

Objective

This study presents the clinical phenotypes and genetic analysis of seven patients with benign familial infantile epilepsy (BFIE) diagnosed by whole-exome sequencing.

Methods

The clinical data of seven children with BFIE diagnosed at the Department of Neurology, Children's Hospital Affiliated to Zhengzhou University between December 2017 and April 2022 were retrospectively analyzed. Whole-exome sequencing was used to identify the genetic causes, and the variants were verified by Sanger sequencing in other family members.

Results

The seven patients with BFIE included two males and five females ranging in age between 3 and 7 months old. The main clinical phenotype of the seven affected children was the presence of focal or generalized tonic-clonic seizures, which was well controlled by anti-seizure medication. Cases 1 and 5 exhibited predominantly generalized tonic-clonic seizures accompanied by focal seizures while cases 2, 3, and 7 displayed generalized tonic-clonic seizures, and cases 4 and 6 had focal seizures. The grandmother and father of cases 2, 6, and 7 had histories of seizures. However, there was no family history of seizures in the remaining cases. Case 1 carried a de novo frameshift variant c.397delG (p.E133Nfs*43) in the proline-rich transmembrane protein 2 (PRRT2) gene while case 2 had a nonsense variant c.46G > T (p.Glu16*) inherited from the father, and cases 3-7 carried a heterozygous frameshift variant c.649dup (p.R217Pfs*8) in the same gene. In cases 3 and 4, the frameshift variant was de novo, while in cases 5-7, the variant was paternally inherited. The c.397delG (p.E133Nfs*43) variant is previously unreported.

Conclusion

This study demonstrated the effectiveness of whole-exome sequencing in the diagnosis of BFIE. Moreover, our findings revealed a novel pathogenic variant c.397delG (p.E133Nfs*43) in the PRRT2 gene that causes BFIE, expanding the mutation spectrum of PRRT2.

Efficacy, Tolerability, and Retention of Antiseizure Medications in PRRT2-Associated Infantile Epilepsy

Background and Objectives

Pathogenic variants in PRRT2, encoding for the proline-rich transmembrane protein 2, were identified as the main cause of self-limiting sporadic and familial infantile epilepsy. Reported data on treatment response to antiseizure medications (ASMs) in defined monogenic epilepsies are limited. The aim of this study was to evaluate the treatment response of ASMs in children with monogenic PRRT2-associated infantile epilepsy.

Methods

A multicenter, retrospective, cross-sectional cohort study was conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology criteria. Inclusion criteria were occurrence of infantile seizures and genetic diagnosis of likely pathogenic/pathogenic PRRT2 variants.

Results

Treatment response data from 52 individuals with PRRT2-associated infantile epilepsy with a total of 79 treatments (defined as each use of an ASM in an individual) were analyzed. Ninety-six percent (50/52) of all individuals received ASMs. Levetiracetam (LEV), oxcarbazepine (OXC), valproate (VPA), and phenobarbital (PB) were most frequently administered. Sodium channel blockers were used in 22 individuals and resulted in seizure freedom in all but 1 child, who showed a reduction of more than 50% in seizure frequency. By contrast, treatment with LEV was associated with worsening of seizure activity in 2/25 (8%) treatments and no effect in 10/25 (40%) of treatments. LEV was rated significantly less effective also compared with VPA and PB. The retention rate for LEV was significantly lower compared with all aforementioned ASMs. No severe adverse events were reported, and no discontinuation of treatment was reported because of side effects.

Discussion

In conclusion, a favorable effect of most ASMs, especially sodium channel blockers such as carbamezepine and OXC, was observed, whereas the efficacy and the retention rate of LEV was lower in PRRT2-associated childhood epilepsy. Tolerability in these young children was good for all ASMs reported in the cohort.

Classification of Evidence

This study provides Class IV evidence that in individuals with PRRT2-associated infantile epilepsy, sodium channel blockers are associated with reduced seizure frequency but levetiracetam is not.

Exploring the genetic etiology of drug-resistant epilepsy: incorporation of exome sequencing into practice

BACKGROUND

By affecting about 50 million people worldwide, epilepsy is considered a global concern in neurology. Intolerable enough, up to ¼ of all patients do not respond to antiepileptic drugs and have recurring seizures. Therefore, revealing the underlying etiology is quite demanding in a clinical context to improve diagnosis and disease management.

METHODS

Initially, 85 patients suspected of epilepsy underwent thorough clinical and paraclinical evaluation and 24 individuals with drug-resistant epilepsy entered the study. Using whole-exome sequencing, the genetic etiology of drug-resistant epilepsy was investigated and discerned whether this method could facilitate the management of drug-resistant epilepsy through personalized medicine. Eventually, functional annotation was performed and drug-gene interaction networks were constructed to find potential therapeutic targets.

RESULTS

We found eleven novel variants in various genes including IRF2BPL, ST3GAL3, and GPAA1, for which a few epilepsy-related variants are available in public databases. The overall diagnostic yield for likely pathogenic and pathogenic variants and the detection rate of novel variants were 25% and 84.6%, respectively. Based on the results, two patients were considered potential candidates for personalized medicine. The highest number of interaction with drugs was demonstrated for SCN1A, SCN2A, and GRIN2A genes.

CONCLUSIONS

This study highlighted the importance of consanguineous marriage in drug-resistant epilepsy and suggested the possibility of reduced penetrance and variable expressivity in some of the autosomal dominant cases. We also suggest that whole-exome sequencing could facilitate personalized management of drug-resistant epilepsy. Regarding drug-gene interactions, some genes such as SCN1A and SCN2A might serve as therapeutic targets in drug-resistant epilepsy.

Effectiveness and Safety of Oxcarbazepine vs. Levetiracetam as Monotherapy for Infantile Focal Epilepsy: A Longitudinal Cohort Study

Objective

This study aimed to compare the effectiveness and safety of oxcarbazepine (OXC) vs. levetiracetam (LEV) for treating infantile focal epilepsy in a longitudinal cohort study.

Methods

We enrolled 187 consecutive patients aged 2–24 months who received OXC or LEV as initial monotherapy; 161 patients completed the study. The longitudinal analysis involved anti-seizure medication (ASM) responsiveness, safety, the establishment of epilepsy syndrome, and etiology over a median follow-up of 2 years (interquartile range [IQR] 1.6–2.4). The relative efficacy and retention rates of OXC vs. LEV were evaluated using generalized linear regression models and the Cox proportional hazards model.

Results

The 161 patients who completed the study had comparable baseline demographics and clinical variables between the OXC group (n = 83) and LEV group (n = 78). Overall, the mean age at onset was 6 months (IQR 4.3–9). The most common epilepsy syndrome was self-limited familial/non-familial infantile epilepsy (54.7%). Epilepsy was related to genetic and unknown causes in 34.2 and 52.2% of the patients, respectively. OXC achieved significantly higher responses than LEV for seizure freedom (risk ratio [RR] = 1.71, 95% confidence interval [CI] = 1.28–2.73, P &lt; 0.001) and 12-month retention rate after onset (hazard ratio [HR] = 1.84, 95% CI = 1.15–2.95, P = 0.007). Moreover, OXC showed more obvious effects for patients aged &lt; 1 year diagnosed with self-limited familial/non-familial infantile epilepsy and non-syndromic epilepsy with genetic or unknown causes. The adverse events related to both OXC and LEV were well-tolerated.

Significance

OXC could be an alternative to LEV for treating infantile focal epilepsy. OXC monotherapy can be considered first-line treatment for patients aged &lt;12 months and those with epilepsy without developmental and epileptic encephalopathy.

Clinical characteristics and genetics of ten Chinese children with PRRT2-associated neurological diseases

BACKGROUND

Proline-rich transmembrane protein 2 (PRRT2) plays an important role in the central nervous system and mutations in the gene are implicated in a variety of neurological disorders. This study aimed to summarize the clinical characteristics and gene expression analysis of neurological diseases related to the PRRT2 gene and explore the clinical characteristics, therapeutic effects, and possible pathogenic mechanisms of related diseases.

METHODS

We enrolled 10 children with PRRT2 mutation-related neurological diseases who visited the Children's Hospital affiliated with the Shanghai Jiaotong University School of Medicine/Shanghai Children's Hospital between May 2017 and February 2022. Video electroencephalography (VEEG), cranial imaging, treatment regimens, gene results, and gene expression were analyzed. Genetic testing involved targeted sequencing or whole-exome genome sequencing (WES). We further analyzed the expression and mutation conservation of PRRT2 and synaptosome-associated protein 25 (SNAP25) in blood samples using quantitative polymerase chain reaction (qPCR) and predicted the protein structure. Summary analysis of the reported gene maps and domains was also performed.

RESULTS

Ten children with PRRT2 gene mutations were analyzed, and 4 mutations were identified, consisting of 2 new (c.518A > C, p.Glu173 Ala; c.879 + 112G > A, p.?) and two known (c. 649 dup, p. Arg217Profs * 8; c. 649 del, p. Arg217Glufs * 12) mutations. Among these mutations, one was de novo(P6), and three could not be determined because one parent refused genetic testing. The clinical phenotypes were paroxysmal kinesigenic dyskinesia (PKD), benign familial infantile epilepsy (BFIE), epilepsy, infantile spasms, and intellectual disability. The qPCR results showed that PRRT2 gene expression levels were significantly lower in children and parent carriers than the control group. The SNAP25 gene expression level of affected children was significantly lower (P ≤ 0.001) than that of the control group. The mutation sites reported in this study are highly conserved in different species. Among the various drugs used, oxcarbazepine and sodium valproate were the most effective. All 10 children had a good disease prognosis, and 8 were completely controlled with no recurrence, whereas 2 had less severe and fewer seizures.

CONCLUSION

Mutation of PRRT2 led to a significant decrease in its protein expression level and that of SNAP25, suggesting that the mutant protein may lead to the loss of its function and that of related proteins. This mutation site is highly conserved in most species, and there was no significant correlation between specific PRRT2 genotypes and clinical phenotypes. Asymptomatic carriers also have decreased gene expression levels, suggesting that more factors are involved.

Monogenic Epilepsies: Disease Mechanisms, Clinical Phenotypes, and Targeted Therapies

A monogenic etiology can be identified in up to 40% of people with severe epilepsy. To address earlier and more appropriate treatment strategies, clinicians are required to know the implications that specific genetic causes might have on pathophysiology, natural history, comorbidities, and treatment choices. In this narrative review, we summarize concepts on the genetic epilepsies based on the underlying pathophysiologic mechanisms and present the current knowledge on treatment options based on evidence provided by controlled trials or studies with lower classification of evidence. Overall, evidence robust enough to guide antiseizure medication (ASM) choices in genetic epilepsies remains limited to the more frequent conditions for which controlled trials and observational studies have been possible. Most monogenic disorders are very rare and ASM choices for them are still based on inferences drawn from observational studies and early, often anecdotal, experiences with precision therapies. Precision medicine remains applicable to only a narrow number of patients with monogenic epilepsies and may target only part of the actual functional defects. Phenotypic heterogeneity is remarkable, and some genetic mutations activate epileptogenesis through their developmental effects, which may not be reversed postnatally. Other genes seem to have pure functional consequences on excitability, acting through either loss- or gain-of-function effects, and these may have opposite treatment implications. In addition, the functional consequences of missense mutations may be difficult to predict, making precision treatment approaches considerably more complex than estimated by deterministic interpretations. Knowledge of genetic etiologies can influence the approach to surgical treatment of focal epilepsies. Identification of germline mutations in specific genes contraindicates surgery while mutations in other genes do not. Identification, quantification, and functional characterization of specific somatic mutations before surgery using CSF liquid biopsy or after surgery in brain specimens will likely be integrated in planning surgical strategies and reintervention after a first unsuccessful surgery as initial evidence suggests that mutational load may correlate with the epileptogenic zone. Promising future directions include gene manipulation by DNA or mRNA targeting; although most are still far from clinical use, some are in early phase clinical development.

Sodium channel blockers are effective for benign infantile epilepsy

OBJECTIVE

To examine the efficacy and tolerance of the antiseizure medications lacosamide (LCM) and levetiracetam (LEV) in patients with benign infantile epilepsy (BIE).

METHODS

The clinical data of 24 children with BIE seen between 2014 and 2020 were collected retrospectively, and treatment, effectiveness, and adverse effects were examined. PRRT2 gene analysis was performed using Sanger sequencing.

RESULTS

Of the 24 children with BIE, 14 were treated with antiseizure medications. PRRT2 gene analysis was performed in 14 children, and mutations were identified in 4, including a pair of siblings. All five children treated with LCM became seizure-free, similar to those treated with carbamazepine. The LCM does was 2 mg/kg/day in all cases. There were no adverse effects in any patient treated with LCM. By contrast, both patients treated with LEV had seizure recurrence. In one patient, LEV was replaced with CBZ, resulting in seizure freedom.

CONCLUSIONS

Low-dose LCM was effective and well tolerated in patients with BIE, whereas LEV was insufficiently effective.

PRRT2 variants and effectiveness of various antiepileptic drugs in self-limited familial infantile epilepsy

PURPOSE

Self-limited familial infantile epilepsy (SFIE) is largely associated with variants in proline-rich transmembrane protein 2 (PRRT2). However, the detailed phenotype-genotype correlations are unclear, along with the efficacy of various antiepileptic drugs in the treatment of this epilepsy syndrome. In this study, we analysed the PRRT2 variants associated with SFIE in Chinese patients, and the efficacy of different antiepileptic drugs prescribed during follow-up.

METHODS

We retrospectively included 20 patients diagnosed with SFIE and reviewed their clinical characteristics, genetic variants, and treatment responses.

RESULTS

Eighteen of the 20 (90%) patients harboured the common heterozygous variant of PRRT2 c.649dupC p.(Arg217fs). One patient had two heterozygous variants of PRRT2, c.640G>C p.(Ala214Pro) and c.955G>T p.(Val319Leu), and the other patient harboured a novel c.606delA (p.Pro203Hisfs) variant. Nine patients who had first-line treatment of oxcarbazepine (OXC) became seizure-free. However, initial treatment with levetiracetam (LEV) or sodium valproate (VPA) in eight and three patients, respectively, was not effective even after increasing the dosage, and seizure-free status was only achieved after changing the treatment to OXC. The treatment responses suggested a significant difference (P < 0.001) between OXC and other anti-epileptic drugs.

CONCLUSION

OXC as a sodium channel blocker may have a better effect than LEV and VPA in the treatment of PRRT2-associated SFIE. PRRT2 variants may be used as a biomarker to help select antiepileptic drugs for SFIE.

PRRT2 Related Epilepsies: A Gene Review

PRRT2 encodes for proline-rich transmembrane protein 2 involved in synaptic vesicle fusion and presynaptic neurotransmitter release. Mutations in human PRRT2 have been related to paroxysmal kinesigenic dyskinesia (PKD), infantile convulsions with choreoathetosis, benign familial infantile epilepsies, and hemiplegic migraine. PRRT2 mutations cause neuronal hyperexcitability, which could be related to basal ganglia or cortical circuits dysfunction, leading to paroxysmal disorders. PRRT2 is expressed in the cerebral cortex, basal ganglia, and cerebellum. Approximately, 90% of pathogenic variants are inherited and 10% are de novo. Paroxysmal attacks in PKD are characterized by dystonia, choreoathetosis, and ballismus. In the benign familial infantile epilepsy (BFIE), seizures are usually focal with or without generalization, usually begin between 3 and 12 months of age and remit by 2 years of age. In 30% of cases of PRRT2-associated PKD, there is an association with BFIE, and this entity is referred to as PKD with infantile convulsions (PKD/IC). PRRT2 mutations are the cause of benign family childhood epilepsy and PKD/IC. On the other hand, PRRT2 mutations do not seem to correlate with other types of epilepsy. The increasing incidence of hemiplegic migraine in families with PRRT2-associated PKD or PKD/IC suggests a common disease pathway, and it is possible to assert that BFIE, paroxysmal kinesigenic dyskinesia, and PKD with IC belong to a continuous disease spectrum of PRRT2-associated diseases.

The Spectrum of PRRT2-Associated Disorders: Update on Clinical Features and Pathophysiology

Mutations in the PRRT2 (proline-rich transmembrane protein 2) gene have been identified as the main cause of an expanding spectrum of disorders, including paroxysmal kinesigenic dyskinesia and benign familial infantile epilepsy, which places this gene at the border between epilepsy and movement disorders. The clinical spectrum has largely expanded to include episodic ataxia, hemiplegic migraine, and complex neurodevelopmental disorders in cases with biallelic mutations. Prior to the discovery of PRRT2 as the causative gene for this spectrum of disorders, the sensitivity of paroxysmal kinesigenic dyskinesia to anticonvulsant drugs regulating ion channel function as well as the co-occurrence of epilepsy in some patients or families fostered the hypothesis this could represent a channelopathy. However, recent evidence implicates PRRT2 in synapse functioning, which disproves the "channel hypothesis" (although PRRT2 modulates ion channels at the presynaptic level), and justifies the classification of these conditions as synaptopathies, an emerging rubric of brain disorders. This review aims to provide an update of the clinical and pathophysiologic features of PRRT2-associated disorders.

The Genotype and Phenotype of Proline-Rich Transmembrane Protein 2 Associated Disorders in Chinese Children

Objectives: To study the genetic and clinical characteristics of Chinese children with pathogenic proline-rich transmembrane protein 2 (PRRT2) gene-associated disorders. Methods: Targeted next generation sequencing (NGS) was used to identify pathogenic PRRT2 variations in Chinese children with epilepsy and/or kinesigenic dyskinesia. Patients with confirmed PRRT2-associated disorders were monitored and their clinical data were analyzed. Results: Forty-four patients with pathogenic PRRT2 variants were recruited. Thirty-five of them (79.5%) had heterozygous mutations, including 30 frameshifts, three missenses, one nonsense, and one splice site variant. The c.649dupC was the most common variant (56.8%). Eight patients (18.2%) showed whole gene deletions, and one patient (2.3%) had 16p11.2 microdeletion. Thirty-four cases (97.1%) were inherited and one case (2.9%) was de novo. Forty patients were diagnosed with benign familial infantile epilepsy (BFIE), two patients had paroxysmal kinesigenic dyskinesia (PKD) and two had infantile convulsions and choreoathetosis (ICCA). Patients with whole gene deletions had a later remission than patients with heterozygous mutations (13.9 vs. 7.1 months, P = 0.001). Forty-two patients were treated with antiseizure medications (ASMs). At last follow-up, 35 patients, including one who did not receive therapy, were asymptomatic, and one patient without ASMs died of status epilepticus at 12 months of age. One patient developed autism, and one patient showed mild developmental delay/intellectual disability. Conclusion: Our data suggested that patients with whole gene deletions could have more severe manifestations in PRRT2-associated disorders. Conventional ASMs, especially Oxcarbazepine, showed a good treatment response.

Paroxysmal dyskinesia and epilepsy in pseudohypoparathyroidism

Background

Paroxysmal kinesigenic dyskinesia (PKD) and epilepsy share common pathogenic mechanisms but their pathophysiological connections remain unknown. Our study reports an individual with both disorders as a consequence of pseudohypoparathyroidism (PHP). This observation suggests potential shared pathophysiological mechanisms between PKD and epilepsy.

Methods

We report the case of a 15‐year‐old male with pre‐diagnosed PKD and symptomatic epilepsy. We recorded the symptoms and carried out comprehensive biochemical, genetic, imaging, and EEG analyses to examine the characteristics and potentially shared etiology of these conditions.

Results

In this case, the patient's PKD and symptomatic epilepsy were secondary to pseudohypoparathyroidism (PHP). The patient had a seven‐year history of intermittent, involuntary paroxysmal episodic movements, and a six‐year history of a loss of consciousness with convulsions. The electroencephalography results showed that the paroxysmal low and medium amplitude slow waves, isolated sharp waves, and sharp slow‐wave release occurred in the right prefrontal temporal cortex. Serum analysis indicated a calcium concentration of 1.91 mmol/L, a phosphorus concentration of 2.68 mmol/L, an alkaline phosphatase concentration of 114 IU/L, and a parathyroid hormone concentration of 109 pg/ml. Computerized tomography and magnetic resonance imaging results showed multiple calcifications in the bilateral frontal and parietal lobe cortex, bilateral thalamus, basal ganglia, and centrum semiovale. Furthermore, GNAS methylation abnormalities were discovered during methylation testing. There was no recurrence of abnormal movements or epileptic seizures, and calcium concentrations returned to healthy levels, following the pharmacological treatment of PHP.

Conclusion

In this case, PKD and symptomatic epilepsy were caused by PHP. This report underscores the importance of looking for biochemical abnormalities in PKD and symptomatic epilepsy patients. We suggest that all such intractable epilepsy seizure patients should be screened for PHP.