Paroxysmal kinesigenic dyskinesia in a patient with a PRRT2 mutation and centrotemporal spike discharges on electroencephalogram: case report of a 10-year-old girl

Exploring epileptic phenotypes in PRRT2-related disorders: A report of two cases and literature appraisal

BACKGROUND

The proline-rich transmembrane protein 2 (PRRT2) is a synaptic protein involved in neurotransmitter vesicle release. PRRT2 protein is highly expressed in the cerebellum, cerebral cortex, basal ganglia, and hippocampus. Variants in PRRT2 have been identified as a cause of several neurological disorders, including epilepsy, movement disorders, and headache.

METHODS

We report two families carrying two distinct PRRT2 mutations showing childhood onset of movement disorders, headache, and epilepsy. Demographics, clinical, EEG, neuroimaging, and genetic sequencing study data were collected. A systematic review of the literature was also performed to dissect the most frequently reported PRRT2-associated epileptic phenotypes.

RESULTS

two variants in PRRT2 gene (NM_145239.3:c718C>T, p.Arg240Ter; c.649dupC, p.Arg217Profs*8) were identified. The two variants altered the same extracellular domain of PRRT2. The de novo PRRT2 mutation (c718C>T, p.Arg240Ter) was related to multi-drug-resistant epilepsy. According to the literature, homozygous, biallelic variants and 16p11.2 deletions lead to PRRT2 haploinsufficiency and a more severe phenotype.

CONCLUSIONS

PRRT2 mutations can be associated with several epileptic phenotypes ranging from benign ASM-responsive form to more severe epileptic encephalopathies. Identifying PRRT2 variants in epilepsy patients may help achieve more personalized treatment approaches. However, phenotype-genotype correlations remain a challenge.

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.

Case Report: A Case of Concomitant Paroxysmal Kinesigenic Dyskinesia and Epilepsy: Can We Treat Two Birds With One Stone?

Background

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent episodes of movement-induced motor attacks. PKD patients may have concomitant epilepsy. Differentiation between the two disorders and effective control of both diseases remain challenging.

Case Presentation

We present a Chinese girl with typical manifestations of PKD, who also suffered from generalized tonic-clonic seizure attacks at the same time. Genetic testing confirmed a PRRT2 mutation (c.649dupC). Oxcarbazepine was initially used, but withdrawn due to a hypersensitivity reaction. Levetiracetam was initiated afterwards, which was effective for seizures but failed to control her PKD symptoms. The addition of lacosamide (LCM) completely controlled her PKD symptoms.

Conclusion

This is the first case reporting the effectiveness of LCM for concomitant PKD and epilepsy. Our case proposes a novel alternative for such patients who are resistant or cannot tolerate conventional anti-sodium antiepileptics.

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.

A Child Who Suddenly Freezes While Trying to Cross Crosswalks-Unique Clinical Manifestation of Paroxysmal Kinesigenic Dyskinesia: A Case Report

(1) Background: We report the case of a patient with a unique clinical presentation of inability to cross crosswalks due to paroxysmal kinesigenic dyskinesia (PKD). (2) Case presentation: A 14-year-old boy presented with the inability to move his right leg at gait initiation from the standing position. This episode lasted for approximately 20–30 s and manifested 1–3 times a day. The difficulty in gait initiation usually occurred when the patient tried to cross crosswalks when the traffic light turned from red to blue. His right arm stiffened occasionally while trying to write with a pencil and eat food with a spoon or chopsticks. Other neurological manifestations and pain were absent during these episodes. No neurological symptoms were observed between the attacks. Brain magnetic resonance imaging did not reveal any abnormalities. A next-generation sequencing study revealed a pathological variant in the proline-rich transmembrane protein 2 (PRRT2) gene. The patient was diagnosed with PKD. His symptoms disappeared completely after treatment with carbamazepine (100 mg/day). (3) Conclusions: The symptoms of PKD can be successfully controlled using antiepileptic medications. Therefore, clinicians should be aware of the clinical manifestations of PKD to provide appropriate treatment.

PRRT2 gene variant in a child with dysmorphic features, congenital microcephaly, and severe epileptic seizures: genotype-phenotype correlation?

Background

Mutations in Proline-rich Transmembrane Protein 2 (PRRT2) have been primarily associated with individuals presenting with infantile epilepsy, including benign familial infantile epilepsy, benign infantile epilepsy, and benign myoclonus of early infancy, and/or with dyskinetic paroxysms such as paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, and exercise-induced dyskinesia. However, the clinical manifestations of this disorder vary widely. PRRT2 encodes a protein expressed in the central nervous system that is mainly localized in the pre-synaptic neurons and is involved in the modulation of synaptic neurotransmitter release. The anomalous function of this gene has been proposed to cause dysregulation of neuronal excitability and cerebral disorders.

Case presentation

We hereby report on a young child followed-up for three years who presents with a spectrum of clinical manifestations such as congenital microcephaly, dysmorphic features, severe intellectual disability, and drug-resistant epileptic encephalopathy in association with a synonymous variant in PRRT2 gene (c.501C > T; p.Thr167Ile) of unknown clinical significance variant (VUS) revealed by diagnostic exome sequencing.

Conclusion

Several hypotheses have been advanced on the specific role that PRRT2 gene mutations play to cause the clinical features of affected patients. To our knowledge, the severe phenotype seen in this case has never been reported in association with any clinically actionable variant, as the missense substitution detected in PRRT2 gene. Intriguingly, the same mutation was reported in the healthy father: the action of modifying factors in the affected child may be hypothesized. The report of similar observations could extend the spectrum of clinical manifestations linked to this mutation.

Paroxysmal movement disorders - practical update on diagnosis and management

Introduction: Paroxysmal dyskinesias and episodic ataxias are often caused by mutations in genes related to cell membrane and synaptic function. Despite the exponential increase in publications of genetically confirmed cases, management remains largely clinical based on non-systematic evidence. Areas covered: The authors provide a historical and clinical review of the main types of paroxysmal dyskinesias and episodic ataxias, with recommendations for diagnosis and management of patients suffering from these conditions. Expert opinion: After secondary paroxysmal dyskinesias, the most common paroxysmal movement disorders are likely to be PRRT2-associated paroxysmal kinesigenic dyskinesias, which respond well to small doses of carbamazepine, and episodic ataxia type 2, which often responds to acetazolamide. Familial paroxysmal non-kinesigenic dyskinesias are largely caused by mutations in PNKD and have poor response to therapy but improve with age. Exercise-induced dyskinesias are genetically heterogeneous, caused by disorders of glucose transport, mitochondrial function, dopaminergic pathways or neurodegenerative conditions amongst others. GNAO1 and ADCY5 mutations can also cause paroxysmal movement disorders, often in the context of ongoing motor symptoms. Although a therapeutic trial is justified for classic cases and in limited resource settings, genetic testing may help direct initial or rescue therapy. Deep brain stimulation may be an option for severe cases.

PRRT2 mutations in a cohort of Chinese families with paroxysmal kinesigenic dyskinesia and genotype-phenotype correlation reanalysis in literatures

PURPOSE OF THE STUDY

Though rare, children are susceptible to paroxysmal dyskinesias such as paroxysmal kinesigenic dyskinesia, and infantile convulsions and choreoathetosis. Recent studies showed that the cause of paroxysmal kinesigenic dyskinesia or infantile convulsions and choreoathetosis could be proline-rich transmembrane protein 2 (PRRT2) gene mutations.

MATERIAL AND METHODS

This study analysed PRRT2 gene mutations in 51 families with paroxysmal kinesigenic dyskinesia or infantile convulsions and choreoathetosis by direct sequencing. In particular, we characterize the genotype-phenotype correlation between age at onset and the types of PRRT2 mutations in all published cases.

RESULTS

Direct sequencing showed that 12 out of the 51 families had three different pathogenic mutations (c.649dupC, c.776dupG, c.649C>T) in the PRRT2 gene. No significant difference of age at onset between the patients with and without PRRT2 mutations was found in this cohort of patients. A total of 97 different PRRT2 mutations have been reported in 87 studies till now. The PRRT2 mutation classes are wide, and most mutations are frameshift mutations but the most common mutation remains c.649dupC. Comparisons of the age at onset in paroxysmal kinesigenic dyskinesia or infantile convulsions patients with different types of mutations showed no significant difference.

CONCLUSIONS

This study expands the clinical and genetic spectrums of Chinese patients with paroxysmal kinesigenic dyskinesia and infantile convulsions and choreoathetosis. No clear genotype-phenotype correlation between the age at onset and the types of mutations has been determined.