Re-evaluation of PRRT2 mutations in paroxysmal disorders

Mutations in PRRT2 have recently been identified as the major cause of autosomal dominant benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis syndrome (ICCA), and paroxysmal kinesigenic dyskinesia (PKD). Other paroxysmal disorders like febrile seizures, migraine, paroxysmal exercise-induced dyskinesia, and paroxysmal non-kinesigenic dyskinesia have also been shown to be associated with this gene. We re-evaluated PRRT2 mutations and genetic–clinical correlations in additional cases with PKD/ICCA and other paroxysmal disorders. Two novel mutations in PRRT2 were revealed in PKD/ICCA cases, while no mutations were detected in other diseases, which suggests BFIE and PKD are still core phenotypes of PRRT2-related spectrum disorders.     

Familial PRRT2 mutation with heterogeneous paroxysmal disorders including paroxysmal torticollis and hemiplegic migraine

PRRT2 is the gene recently associated with paroxysmal kinesigenic dyskinesia (PKD), benign familial infantile epilepsy, and choreoathetosis infantile convulsions. We report four family members with PRRT2 mutations who had heterogeneous paroxysmal disorders. The index patient had transient infantile paroxysmal torticollis, then benign infantile epilepsy that responded to carbamazepine. The index patient's father had PKD and migraine with aphasia, and his two brothers had hemiplegic migraine with onset in childhood. All four family members had the same PRRT2 c.649dupC mutation. We conclude that heterogeneous paroxysmal disorders are associated with PRRT2 mutations and include paroxysmal torticollis and hemiplegic migraine. We propose that PRRT2 is a new gene for hemiplegic migraine.     

Missense mutations of the proline-rich transmembrane protein 2 gene cosegregate with mild paroxysmal kinesigenic dyskinesia and infantile convulsions in a Chinese pedigree

Paroxysmal kinesigenic dyskinesia is an autosomal dominant dystonia induced by sudden voluntary movements. Recently, proline-rich transmembrane protein 2 (PRRT2) gene mutations, especially frameshift mutations, were described for PKD. In our study, we have collected a three-generation paroxysmal kinesigenic dyskinesia-infantile convulsions pedigree in Tianjin, North China. The symptoms of six patients varied; age of onset decreased in each generation. Mutations in the PRRT2 gene in nine PKD family members were screened by PCR sequencing of genomic DNA samples. Missense mutations of the PRRT2 gene were found in all four PKD patients and two children with infantile convulsions. All six individuals carried heterozygous codon 138 (Pro/Ala) and codon 306 (Ala/Asp) mutations. Missense mutations of the PRRT2 gene other than truncate and frameshift mutations were account for PKD and/or infantile convulsions. Age of onset and symptoms were not necessarily associated with PRRT2 mutations.     

Acute-Onset Ataxia and Transient Cerebellar Diffusion Restriction Associated with a PRRT2 Mutation

PRRT2 gene mutations cause paroxysmal kinesigenic dyskinesia (PKD), infantile convulsions, hemiplegic migraine, and episodic ataxia. A 21-year-old woman reported an episode of dizziness and ataxic gait occurring after swimming. Brain MRI showed a hyperintense cerebellar lesion on diffusion-weighted imaging (DWI) with decreased apparent diffusion coefficient. The clinical course was favorable. Both clinical and MRI abnormalities regressed. Her brother had presented PKD since adulthood. A C.649dupC PRRT2 truncating mutation was identified in both patients. To our knowledge, this is the first case of an acute cerebellar ataxia associated with heterozygous PRRT2 mutation and transient cerebellar hyperintensity on DWI. Among the clinical and genetic heterogeneities of familial paroxysmal disorders, PRRT2 mutation may be considered in patients with episodic cerebellar ataxia and diffusion restriction on neuroimaging.     

The PRRT2 mutation c.649dupC is the so far most frequent cause of benign familial infantile convulsions

PurposeMutations in the PRRT2 gene have been recently described as a cause of paroxysmal kinesigenic dyskinesia, infantile convulsions with choreoathetosis syndrome and, less often, infantile convulsions. We have analysed the frequency of PRRT2 mutations in families with benign familial infantile convulsions without paroxysmal kinesigenic dyskinesia.Methods and resultsDirect sequencing of the coding region identified the PRRT2 mutation c.649dupC in 5/5 families with infantile convulsions. The mutation was present in 23 family members, of which 18 were clinically affected and 2 were obligate carriers. The affected carriers of this mutation presented with different types of epileptic seizures during early childhood but did not develop additional neurological symptoms later in life.ConclusionOur data demonstrate that the PRRT2 mutation c.649dupC is a frequent cause of benign familial infantile convulsions.     

Benign infantile convulsions (IC) and subsequent paroxysmal kinesigenic dyskinesia (PKD) in a patient with 16p11.2 microdeletion syndrome

Paroxysmal kinesigenic dyskinesia with infantile convulsions (PKD/IC) is caused by mutations in the gene PRRT2 located in 16p11.2. A deletion syndrome 16p11.2 is well established and is characterized by intellectual disability, speech delay, and autism. PKD/IC, however, is extremely rare in this syndrome. We describe a case of PKD/IC and 16p11.2 deletion syndrome and discuss modifiers of PRRT2 activity to explain the rare concurrence of both syndromes.     

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.     

Paroxysmal kinesigenic dyskinesia and infantile convulsions: clinical and linkage studies

OBJECTIVE: To clinically characterize affected individuals in families with paroxysmal kinesigenic dyskinesia (PKD), examine the association with infantile convulsions, and confirm linkage to a pericentromeric chromosome 16 locus. BACKGROUND: PKD is characterized by frequent, recurrent attacks of involuntary movement or posturing in response to sudden movement, stress, or excitement. Recently, an autosomal dominant PKD locus on chromosome 16 was identified. METHODS: The authors studied 11 previously unreported families of diverse ethnic background with PKD with or without infantile convulsions and performed linkage analysis with markers spanning the chromosome 16 locus. Detailed clinical questionnaires and interviews were conducted with affected and unaffected family members. RESULTS: Clinical characterization and sampling of 95 individuals in 11 families revealed 44 individuals with paroxysmal dyskinesia, infantile convulsions, or both. Infantile convulsions were surprisingly common, occurring in 9 of 11 families. In only two individuals did generalized seizures occur in later childhood or adulthood. The authors defined a 26-cM region using linkage data in 11 families (maximum lod score 6.63 at theta = 0). Affected individuals in one family showed no evidence for a shared haplotype in this region, implying locus heterogeneity. CONCLUSIONS: Identification and characterization of the PKD/infantile convulsions gene will provide new insight into the pathophysiology of this disorder, which spans the phenotypic spectrum between epilepsy and movement disorder.     

PRRT2-related disorders: further PKD and ICCA cases and review of the literature

Recent studies reported mutations in the gene encoding the proline-rich transmembrane protein 2 (PRRT2) to be causative for paroxysmal kinesigenic dyskinesia (PKD), PKD combined with infantile seizures (ICCA), and benign familial infantile seizures (BFIS). PRRT2 is a presynaptic protein which seems to play an important role in exocytosis and neurotransmitter release. PKD is the most common form of paroxysmal movement disorder characterized by recurrent brief involuntary hyperkinesias triggered by sudden movements. Here, we sequenced PRRT2 in 14 sporadic and 8 familial PKD and ICCA cases of Caucasian origin and identified three novel mutations (c.919C>T/p.Gln307*, c.388delG/p.Ala130Profs*46, c.884G>A/p.Arg295Gln) predicting two truncated proteins and one probably damaging point mutation. A review of all published cases is also included. PRRT2 mutations occur more frequently in familial forms of PRRT2-related syndromes (80–100 %) than in sporadic cases (33-46 %) suggesting further heterogeneity in the latter. PRRT2 mutations were rarely described in other forms of paroxysmal dyskinesias deviating from classical PKD, as we report here in one ICCA family without kinesigenic triggers. Mutations are exclusively found in two exons of the PRRT2 gene at a high rate across all syndromes and with one major mutation (c.649dupC) in a mutational hotspot of nine cytosines, which is responsible for 57 % of all cases in all phenotypes. We therefore propose that genetic analysis rapidly performed in early stages of the disease is highly cost-effective and can help to avoid further unnecessary diagnostic and therapeutic interventions.     

A locus for paroxysmal kinesigenic dyskinesia maps to human chromosome 16

OBJECTIVE: To use genetic linkage analysis to localize a gene for paroxysmal kinesigenic dyskinesia (PKD) in a three generation African-American kindred. BACKGROUND: PKD is a rare autosomal dominant disorder characterized by episodic choreiform or dystonic movements that are brought on or exacerbated by voluntary movement. There are individuals with the clinical features of PKD but with no family history of the disease, but whether these sporadic cases represent spontaneous mutations of PKD or have a distinct condition is unknown. METHODS: A genome-wide linkage scan of polymorphic microsatellites at 25 cM resolution was performed to localize a gene for PKD in one African-American kindred. Pairwise multipoint linkage analyses were performed at different penetrance estimates. RESULTS: Evidence for linkage of the kinesigenic form of paroxysmal dyskinesia to chromosome 16 was obtained. A maximum lod score of 4.40 at theta = 0 was obtained with D16S419. Critical recombinants place the PKD gene between D16S3100 and D16S771. CONCLUSIONS: A paroxysmal kinesigenic dyskinesia (PKD) locus lies within an 18 cM interval on 16p11.2-q11.2, between D16S3100 and D16S771. A gene for infantile convulsions with paroxysmal choreoathetosis has also been mapped to this region. These two regions overlap by approximately 6 cM. These two diseases could be caused by different mutations in the same gene or two distinct genes may lie within this region.     

A new case of concurrent existence of PRRT2-associated paroxysmal movement disorders with c.649dup variant and 16p11.2 microdeletion syndrome

BackgroundThe PRRT2 gene located at 16p11.2 encodes proline-rich transmembrane protein 2. In recent reviews, clinical spectrum caused by pathogenic PRRT2 variants is designated as PRRT2-associated paroxysmal movement disorders, which include paroxysmal kinesigenic dyskinesia, benign familial infantile epilepsy, and infantile convulsions with choreoathetosis, and hemiplegic migraine. The recurrent 16p11.2 microdeletion encompassing PRRT2 has also been reported to cause neurodevelopmental syndrome, associated with autism spectrum disorder. Although PRRT2 variants and 16p11.2 microdeletion cause each disease with the autosomal dominant manner, rare cases with bi-allelic PRRT2 variants or concurrent existence of PRRT2 variants and 16p11.2 microdeletion have been reported to show more severe phenotypes.Case reportA 22-year-old man presents with episodic ataxia, paroxysmal kinesigenic dyskinesia, seizure, intellectual disability and autism spectrum disorder. He also has obesity, hypertension, hyperuricemia, and mild liver dysfunction. Exome sequencing revealed a c.649dup variant in PRRT2 in one allele and a de novo 16p11.2 microdeletion in another allele.ConclusionsOur case showed combined clinical features of PRRT2-associated paroxysmal movement disorders and 16p11.2 microdeletion syndrome. We reviewed previous literatures and discussed phenotypic features of patients who completely lack the PRRT2 protein.     

Girl with a PRRT2 mutation and infantile focal epilepsy with bilateral spikes

This paper documents the case of a female Japanese patient with infantile focal epilepsy, which was different from benign infantile seizures, and a family history of infantile convulsion and paroxysmal choreoathetosis. The patient developed partial seizures (e.g., psychomotor arrest) at age 14 months. At the time of onset, interictal electroencephalography (EEG) showed bilateral parietotemporal spikes, but the results of neurologic examination and brain magnetic resonance imaging were normal. Her seizures were well controlled with carbamazepine, and she had a normal developmental outcome. EEG abnormalities, however, persisted for more than 6 years, and the spikes moved transiently to the occipital area and began to resemble the rolandic spikes recognized in benign childhood epilepsy. Her father had paroxysmal kinesigenic dyskinesia, with an onset age of 6 years, and her youngest sister had typical benign infantile seizures. Genetic analysis demonstrated that all affected members had a heterozygous mutation of c.649_650insC in the proline-rich transmembrane protein-2 (PRRT2) gene. This case indicates that the phenotypic spectrum of infantile seizures or epilepsy with PRRT2-related pathology may be larger than previously expected, and that genetic investigation of the effect of PRRT2 mutations on idiopathic seizures or epilepsy in childhood may help elucidate the pathological backgrounds of benign childhood epilepsy.     

Mutations in PRRT2 are not a common cause of infantile epileptic encephalopathies

Heterozygous mutations in PRRT2 have recently been identified as the major cause of autosomal dominant benign familial infantile epilepsy (BFIE), infantile convulsions with choreoathetosis syndrome (ICCA), and paroxysmal kinesigenic dyskinesia (PKD). Homozygous mutations in PRRT2 have also been reported in two families with intellectual disability (ID) and seizures. Heterozygous mutations in the genes KCNQ2 and SCN2A cause the two other autosomal dominant seizure disorders of infancy: benign familial neonatal epilepsy and benign familial neonatal‐infantile epilepsy. Mutations in KCNQ2 and SCN2A also contribute to severe infantile epileptic encephalopathies (IEEs) in which seizures and intellectual disability co‐occur. We therefore hypothesized that PRRT2 mutations may also underlie cases of IEE. We examined PRRT2 for heterozygous, compound heterozygous or homozygous mutations to determine their frequency in causing epileptic encephalopathies (EEs). Two hundred twenty patients with EEs with onset by 2 years were phenotyped. An assay for the common PRRT2 c.649‐650insC mutation and high resolution‐melt analysis for mutations in the remaining exons of PRRT2 were performed. Neither the common mutation nor any other pathogenic variants in PRRT2 were detected in the 220 patients. Our findings suggest that mutations in PRRT2 are not a common cause of IEEs.     

PRRT2 mutation in Japanese children with benign infantile epilepsy

Mutations in PRRT2 genes have been identified as a major cause of benign infantile epilepsy and/or paroxysmal kinesigenic dyskinesia. We explored mutations in PRRT2 in Japanese patients with BIE as well as its related conditions including convulsion with mild gastroenteritis and benign early infantile epilepsy. We explored PRRT2 mutations in Japanese children who had had unprovoked infantile seizures or convulsion with mild gastroenteritis. The probands included 16 children with benign infantile epilepsy, 6 children with convulsions with mild gastroenteritis, and 2 siblings with benign early infantile epilepsy. In addition, we recruited samples from family members when PRRT2 mutation was identified in the proband. Statistical analyses were performed to identify differences in probands with benign infantile epilepsy according to the presence or absence of PRRT2 mutation. Among a total of 24 probands, PRRT2 mutations was identified only in 6 probands with benign infantile epilepsy. A common insertion mutation, c.649_650insC, was found in 5 families and a novel missense mutation, c.981C>G (I327M), in one. The family history of paroxysmal kinesigenic dyskinesia was more common in probands with PRRT2 mutations than in those without mutations. Our study revealed that PRRT2 mutations are common in Japanese patients with benign infantile epilepsy, especially in patients with a family history of paroxysmal kinesigenic dyskinesia.     

Genetic and phenotypic heterogeneity in sporadic and familial forms of paroxysmal dyskinesia

Paroxysmal dyskinesia (PxD) is a group of movement disorders characterized by recurrent episodes of involuntary movements. Familial paroxysmal kinesigenic dyskinesia (PKD) is caused by PRRT2 mutations, but a distinct etiology has been suggested for sporadic PKD. Here we describe a cohort of patients collected from our movement disorders outpatient clinic in the period 1996–2011. Fifteen patients with sporadic PxD and 23 subjects from three pedigrees with familial PKD were screened for mutations in candidate genes. PRRT2 mutations co-segregated with PKD in two families and occurred in two sporadic cases of PKD. No mutations were detected in patients with non-kinesigenic or exertion-induced dyskinesia, and none in other candidate genes including PNKD1 (MR-1) and SLC2A1 (GLUT1). Thus, PRRT2 mutations also cause sporadic PKD as might be expected given the variable expressivity and reduced penetrance observed in familial PKD. Further genetic heterogeneity is suggested by the absence of candidate gene mutations in both sporadic and familial PKD suggesting a contribution of other genes or non-coding regions.     

Lacosamide for children with paroxysmal kinesigenic dyskinesia

ObjectivesThis study was performed to evaluate the efficacy and tolerability of lacosamide (LCM) for paroxysmal kinesigenic dyskinesia (PKD) in children.MethodsWe retrospectively reviewed the medical charts of pediatric PKD patients (aged <16 years) treated with LCM. Data regarding demographic characteristics, proline-rich transmembrane protein 2 (PRRT2) gene variant, clinical features of PKD, dose of LCM, efficacy, and adverse events were recorded.ResultsFour eligible patients (3 males, 1 female) were identified, with an age of onset ranging from 8.3 to 14.7 years. PRRT2 variant was evaluated in three children and a c.649dupC variant was identified in one child with a positive family history. Attacks were bilateral in three children and left-sided in one. Two children had a family history of PKD and one child had a family history of benign infantile epilepsy. Treatment with carbamazepine failed in two children due to drowsiness and auditory disturbance. The initial dose of LCM was 50 mg/day in three children and 100 mg/day in one. All patients were attack-free within a few days. The maintenance dose was mostly similar to the initial dose. No adverse events related to LCM were reported during follow-up.ConclusionsLCM is an effective and well-tolerated treatment for PKD in children, and low-dose treatment may be viable.     

发作性运动诱发性运动障碍一家系临床与遗传学特点

目的探讨家族性发作性运动诱发性运动障碍(paroxysmal kinesigenic dyskinesia,PKD)临床及遗传学特点。方法对1个PKD家系共14名成员进行PRRT2基因检测及调查随访,其中患病2例(1例住院治疗,另1例未治疗),总结分析其临床表现、遗传特点、药物治疗效果及预后。结果该家系2例患者均为男性,患病率14.3%,其中1例不治自愈,1例用卡马西平疗效显著,用拉莫三嗪也有效。该家系为单纯性PKD家系,PRRT2基因检测结果显示该家系中3例存在突变c.797GA(p.266RQ),其中1例无临床症状,符合常染色体显性遗传,伴不全外显,存在遗传早现;该家系合并存在多囊肾家族史。结论单纯家族性PKD抗癫痫药物疗效与突变类型及临床特征有关;治疗方案选择应以临床特点及突变类型为依据。     

Clinical Manifestations in Paroxysmal Kinesigenic Dyskinesia Patients with Proline-Rich Transmembrane Protein 2 Gene Mutation

Background and Purpose

Given the diverse phenotypes including combined non-dyskinetic symptoms in patients harboring mutations of the gene encoding proline-rich transmembrane protein 2 (PRRT2), the clinical significance of these mutations in paroxysmal kinesigenic dyskinesia (PKD) is questionable. In this study, we investigated the clinical characteristics of PKD patients with PRRT2 mutations.

Methods

Familial and sporadic PKD patients were enrolled and PRRT2 gene sequencing was performed. Demographic and clinical data were compared between PKD patients with and without a PRRT2 mutation.

Results

Among the enrolled PKD patients (8 patients from 5 PKD families and 19 sporadic patients), PRRT2 mutations were detected in 3 PKD families (60%) and 2 sporadic cases (10.5%). All familial patients with a PRRT2 gene mutation had the c.649dupC mutation, which is the most commonly reported mutation. Two uncommon mutations (c.649delC and c.629dupC) were detected only in the sporadic cases. PKD patients with PRRT2 mutation were younger at symptom onset and had more non-dyskinetic symptoms than those without PRRT2 mutation. However, the characteristics of dyskinetic movement did not differ between the two groups.

Conclusions

This is the first study of PRRT2 mutations in Korea. The presence of a PRRT2 mutation was more strongly related to familial PKD, and was clinically related with earlier age of onset and common non-dyskinetic symptoms in PKD patients.     

Paroxysmal kinesigenic dyskinesia: cortical or non-cortical origin

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by involuntary dystonia and/or chorea triggered by a sudden movement. Cases are usually familial with an autosomal dominant inheritance. Hypotheses regarding the pathogenesis of PKD focus on the controversy whether PKD has a cortical or non-cortical origin. A combined familial trait of PKD and benign familial infantile seizures has been reported as the infantile convulsions and paroxysmal choreoathetosis (ICCA) syndrome. Here, we report a family diagnosed with ICCA syndrome with an Arg217STOP mutation. The index patient showed interictal EEG focal changes compatible with paroxysmal dystonic movements of his contralateral leg. This might support cortical involvement in PKD.