Genetic analysis of PRRT2 for benign infantile epilepsy, infantile convulsions with choreoathetosis syndrome, and benign convulsions with mild gastroenteritis

Update on benign convulsions with mild gastroenteritis

Benign convulsions with mild gastroenteritis (CwG) are characterized by afebrile convulsions associated with viral gastroenteritis in previously healthy infants and children. The main causative pathogens are rotavirus and norovirus. CwG occurs frequently in both East Asian and Western countries. The prevalence of CwG was reportedly not decreased by the introduction of rotavirus vaccines, and the prevalence of norovirus-associated CwG has been increasing annually. Convulsions in CwG are usually clustered, do not last longer than 5 minutes, and are mostly generalized. Laboratory diagnostics, electroencephalography (EEG), and imaging findings are usually normal. There is a probability of mild, transient abnormal findings on EEG or imaging limited to the acute disease phase. Although several reports have suggested that pathogens that affect the central nervous system through direct or indirect mechanisms could be related to the pathophysiology of CwG, its mechanism is not fully understood. Several antiepileptic drugs are effective during convulsions; however, long-term antiepileptic treatment is not required as CwG usually has a good prognosis.

Case report: A novel de novo variant of SCN8A in a child with benign convulsions with mild gastroenteritis

Benign convulsions with mild gastroenteritis (CwG) is characterized by afebrile convulsions accompanied by mild gastroenteritis, and it can be considered after central nervous system infection, hypoglycemia, electrolyte disturbance, and moderate and severe dehydration are excluded. Previous studies have suggested that genetics may be involved in CWG. Herein, we reported a novel de novo variant of SCN8A in a child with CwG. This is the first report that SCN8A may be associated with CwG. Our report may provides evidence for the genetic etiology of CwG and expands the phenotypic and genetic spectrum of SCN8A-related disorders, which previously included severe developmental and epileptic encephalopathy (DEE) phenotype, benign epilepsy phenotype, spectrum of intermediate epilepsies, and patients with cognitive and/or behavioral disturbances without epilepsy. Phenotype of CwG has a good prognosis, and it does not require long-term antiepileptic therapy. Overtreatment should be avoided clinically. However, the conclusion needs to be further defined by long-term follow-up and similar clinical reports. In spite of this, our clinical observation provides possible evidence for future studies on the relationship between SCN8A and CwG.

Prognostic factors for the recurrence of afebrile seizures after benign convulsions associated with mild gastroenteritis

OBJECTIVE

The overall prognosis of benign convulsions associated with mild gastroenteritis (CwG) is favorable, and the incidence of afebrile seizure recurrence with or without gastroenteritis (ASwGI and ASwoGI, respectively) is low. In this study we investigated the prognostic factors associated with afebrile seizure (AS) relapse after the first CwG episode.

METHODS

A hospital-based cohort with an initial CwG episode from January 2012 to October 2019 was followed for at least 19 months. The relapse types were divided into ASwGI and ASwoGI. Logistic regression analysis was performed to identify the independent prognostic factors for the recurrence of AS after the initial CwG episode. Furthermore, the clinical characteristics between ASwGI and ASwoGI were compared.

RESULTS

Among the 868 patients enrolled, 67 (7.7%) experienced a second AS and 71% (48/67) showed gastroenteritis-associated recurrence. Except for five patients with subsequent epilepsy (0.6%), only eight (0.9%) experienced three seizure episodes. The independent predictive factors for the subsequent recurrence of AS were age less than 18 months at onset (odds ratio [OR]: 2.93, 95% confidence interval [CI]: 1.53-5.63), repeated seizures over 24 h (OR: 4.09, 95% CI: 2.19-7.65), and absence of fever (OR: 2.33, 95% CI: 1.26-4.33) during the first CwG episode. The probability of recurrence of AS for those with one, two, and three predictive factors was 3.23%, 13.35%, and 22.85%, respectively. In addition, the age at onset was significantly lower in the ASwoGI group than in the ASwGI group during the first episode (p < .05).

SIGNIFICANCE

The risk of AS relapse after the initial CwG episode is low, and the majority of patients presented with gastroenteritis. The risk can be predicted by age at onset, repeated seizures over 24 h, and absence of fever during the first CwG episode.

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.

Novel PRRT2 gene variants identified in paroxysmal kinesigenic dyskinesia and benign familial infantile epilepsy in Chinese families

The present study was performed to investigate the clinical manifestations and pathogenic variants in three large families with autosomal dominant paroxysmal kinesigenic dyskinesia (PKD) and/or benign familial infantile epilepsy (BFIE) in China. Detailed clinical data and family history were collected. Genomic DNA was isolated from the peripheral blood samples of all available members. The genetic diagnosis was made by whole-exome sequencing on the three probands and the candidate variants were verified by PCR-Sanger sequencing. The pathogenicity of variants was predicted by bioinformatics analyses and classified according to the American College of Medical Genetics criteria. A total of three causative heterozygous variants were identified in the proline-rich transmembrane protein 2 (PRRT2) gene by DNA sequencing: A novel c.324_334del(p.Val109Argfs*21) deletion variant in Family A, as well as the previously known c.510_513del(p.Ser172Argfs*3) deletion variant in Family B and c.649dupC(p.Arg217Profs*8) duplication variant in Family C. The three variants of PRRT2 co-segregated with the phenotype and genotype in the family members. The present results deepen the current understanding of PKD/BFIE and extend the genotypic-phenotypic spectrum of PKD/BFIE.

Intrafamilial variability in SPTAN1-related disorder: From benign convulsions with mild gastroenteritis to developmental encephalopathy

Mutations in SPTAN1 gene are responsible for a wide spectrum of neurodevelopmental disorders including early-onset epileptic encephalopathy with progressive brain atrophy, severe intellectual disability with cerebellar malformations, and relatively milder phenotypes with or without epilepsy. Herein, we report three affected individuals including two siblings of 13 and 8 years and their 39-year-old mother, carrying a novel pathogenic variant in SPTAN1 gene. The phenotype of the index cases and their mother was remarkable for the variable expressivity, including benign convulsions with mild gastroenteritis, intellectual disability and developmental encephalopathy with epilepsy. Our clinical observation suggests for the first time that variants in SPTAN1 gene might be involved in the aetiology of benign convulsions correlated with mild gastroenteritis.

A Novel PRRT2 Variant in Chinese Patients Suffering from Paroxysmal Kinesigenic Dyskinesia with Infantile Convulsion

PRRT2 mutations are the major causative agent of paroxysmal kinesigenic dyskinesia with infantile convulsion (PKD/IC). The study is aimed at screening PRRT2 gene mutations in patients who suffered from PKD/IC in Chinese population. Thirteen Chinese patients with PKD/IC were screened randomly for coding exons of the PRRT2 gene mutation along with 50 ethnically coordinated control people. Nine (2 unaffected) and 4 of the patients showed familial PKD/IC and apparently sporadic cases, respectively. We identified 5 different PRRT2 mutations in 10 individuals, including 8 familial and 2 apparently sporadic cases. However, no mutations were found in the 50 ethnically matched controls. Unknown (novel) NM_145239.2:c.686G>A and previously reported NM_145239.2:c.743G>C variants were identified in two familial and sporadic patients. All affected members of family A showed mutation NM_145239.2:c.650_670delinsCAATGGTGCCACCACTGGGTTA. The previously identified NM_145239.2:c.412 C>G and NM_145239.2:c.709G>A variants are seen in two individuals assessed in family B. Other than the previously identified variants, some of the patients with PRRT2-PKD/IC showed a new PRRT2 substitution variant. Thus, the spectrum of PRRT2 variants is expanded. The possible role and probability of PRRT2 variants involved in PKD/IC are highlighted.

Novel and de novo point and large microdeletion mutation in PRRT2-related epilepsy

BACKGROUND

Point and copy number variant mutations in the PRRT2 gene have been identified in a variety of paroxysmal disorders and different types of epilepsy. In this study, we analyzed the phenotypes and PRRT2-related mutations in Chinese epilepsy children.

METHODS

A total of 492 children with epilepsy were analyzed by whole exome sequencing (WES) and low-coverage massively parallel CNV sequencing (CNV-seq) to find the single nucleotide variants and copy number variations (CNVs). And quantitative polymerase chain reaction was utilized to verify the CNVs. Their clinical information was followed up.

RESULTS

We found PRRT2-related mutations in 19 patients (10 males and nine females, six sporadic cases and 13 family cases). Twelve point mutations, four whole gene deletion, and three 16p11.2 deletions were detected. The clinical features of 39 patients in 19 families included one early childhood myoclonic epilepsy (ECME), one febrile seizure (FS), two infantile convulsions with paroxysmal choreoathetosis (ICCA), six paroxysmal kinesigenic dyskinesias (PKD), 12 benign infantile epilepsy (BIE), and 17 benign familial infantile epilepsy (BFIE). All patients had normal brain MRI. Interictal EEG showed only one patient had generalized polyspike wave and five patients had focal transient discharges. Focal seizures originating in the frontal region were recorded in one patient, two from the temporal region, and two from the occipital region. Most patients were treated effectively with VPA or OXC, and the child with myoclonic seizures was not sensitive to antiepileptic drugs.

CONCLUSION

PRRT2 mutations can be inherited or de novo, mainly inherited. The clinical spectrum of PRRT2 mutation includes BIE, BFIE, ICCA, PKD, FS, and ECME. The PRRT2-related mutations contained point mutation, whole gene deletion and 16p11.2 deletions, and large microdeletion mutations mostly de novo. It is the first report of PRRT2 mutation found in ECME. Our report expands the mutation and clinical spectrum of PRRT2-related epilepsy.

Functional and Structural Network Disorganizations in Typical Epilepsy With Centro-Temporal Spikes and Impact on Cognitive Neurodevelopment

Epilepsy with Centrotemporal Spikes (ECTS) is the most common form of self-limited focal epilepsy. The pathophysiological mechanisms by which ECTS induces neuropsychological impairment in 15-30% of affected children remain unclear. The objective of this study is to review the current state of knowledge concerning the brain structural and functional changes that may be involved in cognitive dysfunctions in ECTS. Structural brain imaging suggests the presence of subtle neurodevelopmental changes over the epileptogenic zone and over distant regions in ECTS. This structural remodeling likely occurs prior to the diagnosis and evolves over time, especially in patients with cognitive impairment, suggesting that the epileptogenic processes might interfere with the dynamics of the brain development and/or the normal maturation processes. Functional brain imaging demonstrates profound disorganization accentuated by interictal epileptic spikes (IES) in the epileptogenic zone and in remote networks in ECTS. Over the epileptogenic zone, the literature demonstrates changes in term of neuronal activity and synchronization, which are effective several hundred milliseconds before the IES. In the same time window, functional changes are also observed in bilateral distant networks, notably in the frontal and temporal lobes. Effective connectivity demonstrates that the epileptogenic zone constitutes the key area at the origin of IES propagation toward distant cortical regions, including frontal areas. Altogether, structural and functional network disorganizations, in terms of: (i) power spectral values, (ii) functional and effective connectivity, are likely to participate in the cognitive impairment commonly reported in children with ECTS. These results suggest a central and causal role of network disorganizations related to IES in the neuropsychological impairment described in ECTS children.

Clinical outcome of recurrent afebrile seizures in children with benign convulsions associated with mild gastroenteritis

PURPOSE

To assess the clinical outcome and evolution of recurrent afebrile seizures in children initially diagnosed with benign convulsions associated with mild gastroenteritis (CwG).

METHODS

We reviewed and analyzed the medical records of 37 patients who were diagnosed as CwG at onset, followed by recurrent afebrile seizures and followed up for at least 24 months.

RESULTS

The follow-up period ranged from 2 to 7 years (median, 40.1 months).Three patterns of recurrent afebrile seizures were recorded: afebrile seizures associated with gastrointestinal infection (AS-GI, n = 25), afebrile seizures associated with non-gastrointestinal infection (AS-nGI, n = 9), and unprovoked seizures (US, n = 3). Twenty eight patients (75.7%) had a second episode within 6 months after the first seizures. Five cases (13.5%) suffered three episodes of afebrile seizures. Seizure characteristics of the three patterns were similar, manifesting as clustered seizures in the majority. Focal epileptic activities in interictal EEG were found in 3 cases (9.4%) at onset, 10 cases (28.6%) at the second episode, respectively. Six patients were prescribed anti-epileptic drugs with apparently good responses. During at least 2 years' follow-up, all the cases showed normal psychomotor development. Only one patient was diagnosed with epilepsy.

CONCLUSIONS

All the recurrent afebrile seizures initially diagnosed as CwG, irrespective of the kinds and frequency of relapses, showed favorable prognoses. CwG maybe falls within the category of situation-related seizures, rather than epilepsy.

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.

Genetic analysis of benign familial epilepsies in the first year of life in a Chinese cohort

Benign familial epilepsies that present themselves in the first year of life include benign familial neonatal epilepsy (BFNE), benign familial neonatal-infantile epilepsy (BFNIE) and benign familial infantile epilepsy (BFIE). We used Sanger sequencing and targeted next-generation sequencing to detect gene mutations in a Chinese cohort of patients with these three disorders. A total of 79 families were collected, including 4 BFNE, 7 BFNIE, and 68 BFIE. Genetic testing led to the identification of gene mutations in 60 families (60 out of 79, 75.9%). A total of 42 families had PRRT2 mutations, 9 had KCNQ2 mutations, 8 had SCN2A mutations, and 1 had a GABRA6 mutation. In total three of four BFNE families were detected with KCNQ2 mutations. Mutations were detected in all BFNIE families, including 3 KCNQ2 mutations, 3 SCN2A mutations, and 1 PRRT2 mutation. Gene mutations were identified in 50 out of 68 BFIE families (73.5%), including 41 PRRT2 mutations (41 out of 68, 60.3%), 5 SCN2A mutations, 3 KCNQ2 mutations, and 1 GABRA6 mutation. Our results confirmed that mutations in KCNQ2, SCN2A, and PRRT2 are major genetic causes of benign familial epilepsy in the first year of life in the Chinese population. KCNQ2 is the major gene related to BFNE. PRRT2 is the main gene responsible for BFIE.

Genetic and epigenetic mechanisms of epilepsy: a review

Epilepsy is a common episodic neurological disorder or condition characterized by recurrent epileptic seizures, and genetics seems to play a key role in its etiology. Early linkage studies have localized multiple loci that may harbor susceptibility genes to epilepsy, and mutational analyses have detected a number of mutations involved in both ion channel and nonion channel genes in patients with idiopathic epilepsy. Genome-wide studies of epilepsy have found copy number variants at 2q24.2-q24.3, 7q11.22, 15q11.2-q13.3, and 16p13.11-p13.2, some of which disrupt multiple genes, such as NRXN1, AUTS2, NLGN1, CNTNAP2, GRIN2A, PRRT2, NIPA2, and BMP5, implicated for neurodevelopmental disorders, including intellectual disability and autism. Unfortunately, only a few common genetic variants have been associated with epilepsy. Recent exome-sequencing studies have found some genetic mutations, most of which are located in nonion channel genes such as the LGI1, PRRT2, EFHC1, PRICKLE, RBFOX1, and DEPDC5 and in probands with rare forms of familial epilepsy, and some of these genes are involved with the neurodevelopment. Since epigenetics plays a role in neuronal function from embryogenesis and early brain development to tissue-specific gene expression, epigenetic regulation may contribute to the genetic mechanism of neurodevelopment through which a gene and the environment interacting with each other affect the development of epilepsy. This review focused on the analytic tools used to identify epilepsy and then provided a summary of recent linkage and association findings, indicating the existence of novel genes on several chromosomes for further understanding of the biology of epilepsy.

Paroxysmal hypnogenic dyskinesia is associated with mutations in the PRRT2 gene

Objective:

To explore the potential causative genes of paroxysmal hypnogenic dyskinesia (PHD), which was initially considered a subtype of paroxysmal dyskinesia and has been recently considered a form of nocturnal frontal lobe epilepsy (NFLE).

Methods:

Eleven patients with PHD were recruited. Mutations in proline-rich region transmembrane protein-2 (PRRT2), myofibrillogenesis regulator 1 (MR-1), solute carrier family 2, member 1 (SLC2A1), calcium-activated potassium channel alpha subunit (KCNMA1), cholinergic receptor, nicotinic, alpha 4 (CHRNA4), cholinergic receptor, nicotinic, beta 2 (CHRNB2), cholinergic receptor, nicotinic, alpha 2 (CHRNA2), and potassium channel subfamily T member 1 (KCNT1) were screened by direct sequencing.

Results:

Two PRRT2 mutations were identified in patients with typical PHD. A mutation of c.649dupC (p.Arg217ProfsX8) was identified in a patient with PHD and his father who was diagnosed with paroxysmal kinesigenic dyskinesia. An additional mutation of c.640G>C (p.Ala214Pro) was identified in a sporadic patient and his asymptomatic mother. No mutations were found in the other screened genes.

Conclusions:

The present study identified PRRT2 mutations in PHD, extending the phenotypic spectrum of PRRT2 and supporting the classification of PHD as a subtype of paroxysmal dyskinesia but not NFLE. Based on the results of this study, screening for the PRRT2 mutation is recommended in patients with PHD.

The clinical and genetic heterogeneity of paroxysmal dyskinesias

The contributions of different genes to inherited paroxysmal movement disorders are incompletely understood. Gardiner et al. identify mutations in 47% of 145 individuals with paroxysmal dyskinesias, with PRRT2 mutations in 35%, SLC2A1 in 10% and PNKD in 2%. New mutations expand the associated phenotypes and implicate overlapping mechanisms.

Paroxysmal dyskinesia can be subdivided into three clinical syndromes: paroxysmal kinesigenic dyskinesia or choreoathetosis, paroxysmal exercise-induced dyskinesia, and paroxysmal non-kinesigenic dyskinesia. Each subtype is associated with the known causative genes PRRT2, SLC2A1 and PNKD, respectively. Although separate screening studies have been carried out on each of the paroxysmal dyskinesia genes, to date there has been no large study across all genes in these disorders and little is known about the pathogenic mechanisms. We analysed all three genes (the whole coding regions of SLC2A1 and PRRT2 and exons one and two of PNKD) in a series of 145 families with paroxysmal dyskinesias as well as in a series of 53 patients with familial episodic ataxia and hemiplegic migraine to investigate the mutation frequency and type and the genetic and phenotypic spectrum. We examined the mRNA expression in brain regions to investigate how selective vulnerability could help explain the phenotypes and analysed the effect of mutations on patient-derived mRNA. Mutations in the PRRT2, SLC2A1 and PNKD genes were identified in 72 families in the entire study. In patients with paroxysmal movement disorders 68 families had mutations (47%) out of 145 patients. PRRT2 mutations were identified in 35% of patients, SLC2A1 mutations in 10%, PNKD in 2%. Two PRRT2 mutations were in familial hemiplegic migraine or episodic ataxia, one SLC2A1 family had episodic ataxia and one PNKD family had familial hemiplegic migraine alone. Several previously unreported mutations were identified. The phenotypes associated with PRRT2 mutations included a high frequency of migraine and hemiplegic migraine. SLC2A1 mutations were associated with variable phenotypes including paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, episodic ataxia and myotonia and we identified a novel PNKD gene deletion in familial hemiplegic migraine. We found that some PRRT2 loss-of-function mutations cause nonsense mediated decay, except when in the last exon, whereas missense mutations do not affect mRNA. In the PNKD family with a novel deletion, mRNA was truncated losing the C-terminus of PNKD-L and still likely loss-of-function, leading to a reduction of the inhibition of exocytosis, and similar to PRRT2, an increase in vesicle release. This study highlights the frequency, novel mutations and clinical and molecular spectrum of PRRT2, SLC2A1 and PNKD mutations as well as the phenotype–genotype overlap among these paroxysmal movement disorders. The investigation of paroxysmal movement disorders should always include the analysis of all three genes, but around half of our paroxysmal series remain genetically undefined implying that additional genes are yet to be identified.

The contributions of different genes to inherited paroxysmal movement disorders are incompletely understood. Gardiner et al. identify mutations in 47% of 145 individuals with paroxysmal dyskinesias, with PRRT2 mutations in 35%, SLC2A1 in 10% and PNKD in 2%. New mutations expand the associated phenotypes and implicate overlapping mechanisms.

Characteristics of patients with benign partial epilepsy in infancy without PRRT2 mutations

Mutations in the proline-rich transmembrane protein 2 gene (PRRT2) are known to cause clinical symptoms of paroxysmal kinesigenic dyskinesia (PKD), benign partial epilepsy in infancy (BPEI), and infantile convulsions with choreoathetosis (ICCA) syndrome; however, not all patients with BPEI have PRRT2 mutations, and the genetic backgrounds for such patients are still unknown. To characterize BPEI patients without PRRT2 mutations, we analyzed unrelated 63 patients with BPEI. Sanger sequencing identified PRRT2 mutations in 33 probands (52%). The most common insertion, c.649dup, was identified in 28 probands. Two novel truncation mutations, c.232dup and c.503_504del were identified independently. 16p11.2 microdeletion was not detected in patients without PRRT2 mutations. PRRT2 mutation detection rates were 21/31 (68%) and 12/32 (38%) in probands who were positive or negative for family history, respectively, indicating a significant difference between the two groups. In this study, 20 probands with BPEI were negative for family history of BPEI and negative for PRRT2 mutation. BPEI in these probands may be due to complex genetic predispositions. Because the possibility remains that a second gene contributes to BPEI, further studies are necessary in patients with BPEI but no PRRT2 mutation, especially in Asian people.

Long-term follow-up in children with benign convulsions associated with gastroenteritis

BACKGROUND

The outcome of benign convulsions associated with gastroenteritis (CwG) has generally been reported as being excellent. However, these data need to be confirmed in studies with longer follow-up evaluations.

AIM

To assess the long-term neurological outcome of a large sample of children presenting with CwG.

METHODS

We reviewed clinical features of 81 subjects presenting with CwG (1994-2010) from three different Italian centers with a follow-up period of at least 3 years.

RESULTS

Follow-up period ranged from 39 months to 15 years (mean 9.8 years). Neurological examination and cognitive level at the last evaluation were normal in all the patients. A mild attention deficit was detected in three cases (3.7%). Fourteen children (17.3%) received chronic anti-epileptic therapy. Interictal EEG abnormalities detected at onset in 20 patients (24.7%) reverted to normal. Transient EEG epileptiform abnormalities were detected in other three cases (3.7%), and a transient photosensitivity in one (1.2%). No recurrence of CwG was observed. Three patients (3.7%) presented with a febrile seizure and two (2.5%) with an unprovoked seizure, but none developed epilepsy.

CONCLUSIONS

The long-term evaluation of children with CwG confirms the excellent prognosis of this condition, with normal psychomotor development and low risk of relapse and of subsequent epilepsy.

Phenotypes and PRRT2 mutations in Chinese families with benign familial infantile epilepsy and infantile convulsions with paroxysmal choreoathetosis

Background

Mutations in the PRRT2 gene have been identified as the major cause of benign familial infantile epilepsy (BFIE), paroxysmal kinesigenic dyskinesia (PKD) and infantile convulsions with paroxysmal choreoathetosis/dyskinesias (ICCA). Here, we analyzed the phenotypes and PRRT2 mutations in Chinese families with BFIE and ICCA.

Methods

Clinical data were collected from 22 families with BFIE and eight families with ICCA. PRRT2 mutations were screened using PCR and direct sequencing.

Results

Ninety-five family members were clinically affected in the 22 BFIE families. During follow-up, two probands had one seizure induced by diarrhea at the age of two years. Thirty-one family members were affected in the eight ICCA families, including 11 individuals with benign infantile epilepsy, nine with PKD, and 11 with benign infantile epilepsy followed by PKD. Two individuals in one ICCA family had PKD or ICCA co-existing with migraine. One affected member in another ICCA family had experienced a fever-induced seizure at 7 years old. PRRT2 mutations were detected in 13 of the 22 BFIE families. The mutation c.649_650insC (p.R217PfsX8) was found in nine families. The mutations c.649delC (p.R217EfsX12) and c.904_905insG (p.D302GfsX39) were identified in three families and one family, respectively. PRRT2 mutations were identified in all eight ICCA families, including c.649_650insC (p.R217PfsX8), c.649delC (p.R217EfsX12), c.514_517delTCTG (p.S172RfsX3) and c.1023A > T (X341C). c.1023A > T is a novel mutation predicted to elongate the C-terminus of the protein by 28 residues.

Conclusions

Our data demonstrated that PRRT2 is the major causative gene of BFIE and ICCA in Chinese families. Site c.649 is a mutation hotspot: c.649_650insC is the most common mutation, and c.649delC is the second most common mutation in Chinese families with BFIE and ICCA. As far as we know, c.1023A > T is the first reported mutation in exon 4 of PRRT2. c.649delC was previously reported in PKD, ICCA and hemiplegic migraine families, but we further detected it in BFIE-only families. c.904_905insG was reported in an ICCA family, but we identified it in a BFIE family. c.514_517delTCTG was previously reported in a PKD family, but we identified it in an ICCA family. Migraine and febrile seizures plus could co-exist in ICCA families.