Clinical characteristics of paroxysmal nonkinesigenic dyskinesia in serbian family withMyofibrillogenesis regulator 1 gene mutation

Clinical and Genetic Overview of Paroxysmal Movement Disorders and Episodic Ataxias

Paroxysmal movement disorders (PMDs) are rare neurological diseases typically manifesting with intermittent attacks of abnormal involuntary movements. Two main categories of PMDs are recognized based on the phenomenology: Paroxysmal dyskinesias (PxDs) are characterized by transient episodes hyperkinetic movement disorders, while attacks of cerebellar dysfunction are the hallmark of episodic ataxias (EAs). From an etiological point of view, both primary (genetic) and secondary (acquired) causes of PMDs are known. Recognition and diagnosis of PMDs is based on personal and familial medical history, physical examination, detailed reconstruction of ictal phenomenology, neuroimaging, and genetic analysis. Neurophysiological or laboratory tests are reserved for selected cases. Genetic knowledge of PMDs has been largely incremented by the advent of next generation sequencing (NGS) methodologies. The wide number of genes involved in the pathogenesis of PMDs reflects a high complexity of molecular bases of neurotransmission in cerebellar and basal ganglia circuits. In consideration of the broad genetic and phenotypic heterogeneity, a NGS approach by targeted panel for movement disorders, clinical or whole exome sequencing should be preferred, whenever possible, to a single gene approach, in order to increase diagnostic rate. This review is focused on clinical and genetic features of PMDs with the aim to (1) help clinicians to recognize, diagnose and treat patients with PMDs as well as to (2) provide an overview of genes and molecular mechanisms underlying these intriguing neurogenetic disorders.

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.

The spectrum of paroxysmal dyskinesias

Paroxysmal dyskinesias (PxD) comprise a group of heterogeneous syndromes characterized by recurrent attacks of mainly dystonia and/or chorea, without loss of consciousness. PxD have been classified according to their triggers and duration as paroxysmal kinesigenic dyskinesia, paroxysmal nonkinesigenic dyskinesia and paroxysmal exertion-induced dyskinesia. Of note, the spectrum of genetic and nongenetic conditions underlying PxD is continuously increasing, but not always a phenotype–etiology correlation exists. This creates a challenge in the diagnostic work-up, increased by the fact that most of these episodes are unwitnessed. Furthermore, other paroxysmal disorders, included those of psychogenic origin, should be considered in the differential diagnosis. In this review, some key points for the diagnosis are provided, as well as the appropriate treatment and future approaches discussed.

The PNKD gene is associated with Tourette Disorder or Tic disorder in a multiplex family

Tourette Disorder (TD) is a childhood-onset neuropsychiatric and neurodevelopmental disorder characterized by the presence of both motor and vocal tics. The genetic architecture of TD is believed to be complex and heterogeneous. Nevertheless, DNA sequence variants co-segregating with TD phenotypes within multiplex families have been identified. This report examines whole exomes of affected and unaffected individuals in a multiplex TD family to discover genes involved in the TD etiology. We performed whole exome sequencing on six out of nine members in a three-generation TD multiplex family. Putative deleterious sequence variants co-segregating with TD patients were identified by our in-house bioinformatics pipeline. Induced pluripotent stem cells (iPSCs) were generated from one unaffected and two TD affected individuals. Neurons were derived from the iPSCs and biochemical assays were conducted to evaluate possible molecular differences between affected and unaffected. A rare heterozygous nonsense mutation in PNKD was co-segregated with TD in this multiplex family. Transcript and protein levels of the PNKD long isoform were reduced in neurons derived from the individuals with TD due to the nonsense mutation, indicating nonsense-mediated mRNA decay. We demonstrated that the PNKD long isoform monomer oligomerizes with itself as well as interacts with the synaptic active zone protein RIMS1α. We concluded that reduced PNKD long isoform levels are detected in all affected individuals and we provide evidence for a mechanism whereby this might contribute to the TD phenotype.

Paroxysmal Dyskinesias

Paroxysmal dyskinesias (PD) are hyperkinetic movement disorders where patients usually retain consciousness. Paroxysmal dyskinesias can be kinesigenic (PKD), nonkinesigenic (PNKD), and exercise induced (PED). These are usually differentiated from each other based on their phenotypic and genotypic characteristics. Genetic causes of PD are continuing to be discovered. Genes found to be involved in the pathogenesis of PD include MR-1, PRRT2, SLC2A1, and KCNMA1. The differential diagnosis is broad as PDs can mimic psychogenic events, seizure, or other movement disorders. This review also includes secondary causes of PDs, which can range from infections, metabolic, structural malformations to malignancies. Treatment is usually based on the correct identification of type of PD. PKD responds well to antiepileptic medications, whereas PNKD and PED respond to avoidance of triggers and exercise, respectively. In this article, we review the classification, clinical features, genetics, differential diagnosis, and management of PD.

Effective Treatment of Paroxysmal Nonkinesigenic Dyskinesia With Oxcarbazepine

Paroxysmal nonkinesigenic dyskinesia (PNKD) is a rare chronic disorder characterized by intermittent, non-movement-related involuntary movements. The response to currently available therapies is inconsistent and temporary. We describe here a patient with infantile-onset PNKD who failed a number of pharmaceutical agents used alone or in combination. Treatment with oxcarbazepine resulted in a substantial reduction in the frequency and severity of episodes. The patient has been followed for 4 years now, and the outcome of treatment is consistently favorable. Oxcarbazepine has been effective in managing the kinesigenic form of this disorder; however, its use has never been reported in PNKD to our knowledge. Oxcarbazepine is safer and better tolerated than most of the drugs currently used for treating PNKD, but blinded clinical trials are needed to verify its efficacy in the management of this debilitating, often difficult-to-treat disease.

A case of familial paroxysmal nonkinesigenic dyskinesia due to mutation of the PNKD gene in Chinese Mainland

BACKGROUND

Paroxysmal dyskinesia is a rare neurological disorder characterized by paroxysmal movement disorders. Paroxysmal movement disorders include kinesigenic choreoathetosis, nonkinesigenic choreoathetosis or dyskinesia (PNKD), exercise-induced choreoathetosis, and hypnogenic paroxysmal dystonia. There have been some sporadic reports of PNKD occurrences in Chinese Mainland, but none has been reported on familial PNKD. Proband and methods A 32 years old male admitted to the First Affiliated Hospital of Chinese PLA General Hospital, Beijing, China in 2009 with recurrent limb involuntary movements spanning over 30 years was diagnosed with PNKD. Family history was collected to identify if it was a case of familial or sporadic PNKD. Mutation and linkage analysis were performed to identify the pathogenic gene and the localization of the same.

RESULTS

There were five generations of 26 patients, out of which 3 of these patients died. Follow-up was conducted on 17 out of the 23 patients alive and 9 normal family members. The pedigree showed autosomal dominant inheritance, whom could be divided into light, moderate, and severe group according to clinical signs, spontaneous attack and response to drugs. All patients harbored c.20C>T (p.A7V) mutation in exon 1 of the PNKD/MR-1 gene. Preliminary linkage analyses using phenocopy rates of 0.0001 and 0.1 suggested that linkage signal localizes between D2S126 and D2S377. The functional consequence of the mutation in the disease pathogenesis is pending investigation. Conclusions We report the first case of familial paroxysmal non-kinesigenic dyskinesia (PNKD) in Chinese Mainland, which coincidentally is also the largest case of familial PNKD ever reported. This article is part of a Special Issue entitled Brain and Memory.

Paroxysmal dyskinesias revisited: a review of 500 genetically proven cases and a new classification

Paroxysmal movement disorders are a heterogeneous group of conditions manifesting as episodic dyskinesia with sudden onset and lasting a variable duration. Based on the difference of precipitating factors, three forms are clearly recognized, namely, paroxysmal kinesigenic (PKD), non-kinesigenic (PNKD), and exercise induced (PED). The elucidation of the genetic cause of various forms of paroxysmal dyskinesia has led to better clinical definitions based on genotype-phenotype correlations in the familial forms. However, it has been increasingly recognized that (1) there is a marked pleiotropy of mutations in such genes with still expanding clinical spectra; and (2) not all patients clinically presenting with either PKD, PNKD, or PED have mutations in these genes. We aimed to review the clinical features of 500 genetically proven cases published to date. Based on our results, it is clear that there is not a complete phenotypic-genotypic correlation, and therefore we suggest an algorithm to lead the genetic analyses. Given the fact that the reliability of current clinical categorization is not entirely valid, we further propose a novel classification for paroxysmal dyskinesias, which takes into account the recent genetic discoveries in this field.

Dopamine dysregulation in a mouse model of paroxysmal nonkinesigenic dyskinesia

Paroxysmal nonkinesigenic dyskinesia (PNKD) is an autosomal dominant episodic movement disorder. Patients have episodes that last 1 to 4 hours and are precipitated by alcohol, coffee, and stress. Previous research has shown that mutations in an uncharacterized gene on chromosome 2q33-q35 (which is termed PNKD) are responsible for PNKD. Here, we report the generation of antibodies specific for the PNKD protein and show that it is widely expressed in the mouse brain, exclusively in neurons. One PNKD isoform is a membrane-associated protein. Transgenic mice carrying mutations in the mouse Pnkd locus equivalent to those found in patients with PNKD recapitulated the human PNKD phenotype. Staining for c-fos demonstrated that administration of alcohol or caffeine induced neuronal activity in the basal ganglia in these mice. They also showed nigrostriatal neurotransmission deficits that were manifested by reduced extracellular dopamine levels in the striatum and a proportional increase of dopamine release in response to caffeine and ethanol treatment. These findings support the hypothesis that the PNKD protein functions to modulate striatal neuro-transmitter release in response to stress and other precipitating factors.

Paroxysmal non-kinesigenic dyskinesia due to a PNKD recurrent mutation: report of two Southern European families

Paroxysmal non-kinesigenic dyskinesia (PNKD) is an autosomal dominant disorder characterized by attacks of dystonic or choreathetotic movements precipitated by stress, fatigue, coffee, alcohol or menstruation. In this report we present two families with PNKD of Southern European origin carrying a PNKD recurrent mutation. Incomplete penetrance and intrafamilial variability was detected in both families. Treatment with valproic acid and levetiracetam provided favorable response.

Common polymorphisms in dystonia-linked genes and susceptibility to the sporadic primary dystonias

Genes involved in familial dystonia syndromes (DYT genes) are ideal candidates for investigating whether common genetic variants influence the susceptibility to sporadic primary dystonia. To date, there have been few candidate gene studies for primary dystonia and only two DYT genes, TOR1A and THAP1, have been assessed. We therefore employed a haplotype-tagging strategy to comprehensively assess if common polymorphisms in eight DYT genes (TOR1A, TAF1, GCH1, THAP1, MR-1 (PNKD), SGCE, ATP1A3 and PRKRA) confer risk for sporadic primary dystonia. The 230 primary dystonia cases were matched for age and gender to 228 controls, recruited from movement disorder clinics in Brisbane, Australia and the Australian electoral roll. All subjects were genotyped for 56 tagging SNPs and genotype associations were investigated. Modest genotypic associations (P<0.05) were observed for three GCH1 SNPs (rs12147422, rs3759664 and rs10483639) when comparing all cases against controls. Associations were also seen when the cases were stratified based on presentation. Overall, our findings do not support the hypothesis that common TOR1A variants affect susceptibility for sporadic primary dystonia, and that it is unlikely that common variants around the DYT genes confer substantial risk for sporadic primary dystonia. Further work is warranted to follow up the GCH1 SNPs and the subgroup analyses.

Paroxysmal dyskinesias

Paroxysmal movement disorders are a relatively rare and heterogenous group of conditions manifesting as episodic dyskinesia lasting a brief duration. Three forms are clearly recognized, namely, paroxysmal kinesigenic (PKD), nonkinisegenic (PNKD), and exercise induced (PED). There have been major advances in the understanding of the pathophysiological mechanisms and the genetics of these disorders, leading to better clinical definitions based on genotype-phenotype correlations in the familial idiopathic forms. PKD is genetically heterogenous, but there is linkage to chromosome 16 in a number of families. PNKD is due to mutations of the MR-1 gene. PED is genetically heterogenous, but a number of familial and sporadic cases may be due to GLUT-1 gene mutations. The GLUT1 gene-related form of PED may respond to a ketogenic diet. Potassium and calcium channel mutations underlie the 2 main forms of episodic ataxia (EA1 and EA2), whereas benign torticollis of infancy may also be a calcium channel disorder.

Treatment of paroxysmal dyskinesias

IMPORTANCE OF THE FIELD

Paroxysmal dyskinesias represent a heterogeneous group of rare diseases sharing characteristics with two important groups of neurological disorders, the movement disorders and the epilepsies. Their common hallmark is the paroxysmal occurrence of dyskinesias including athetosis, ballism, chorea and dystonia. During the last two decades, various genetic abnormalities have been identified thereby providing insight into the underlying pathophysiology and offering therapeutic opportunities for many of these conditions.

AREAS COVERED IN THIS REVIEW

We summarize the diagnostic criteria of idiopathic and symptomatic paroxysmal dyskinesias and describe their therapeutic options. For the preparation of this review article, an extensive literature search was undertaken using PubMed.

WHAT THE READER WILL GAIN

This review provides a practical guide to the diagnosis and treatment of paroxysmal dyskinesias.

TAKE HOME MESSAGE

The mainstay of therapy is carbamazepine for paroxysmal kinesigenic dyskinesias and clonazepam for the nonkinesigenic dyskinesias. In symptomatic paroxysmal dyskinesias, the treatment of the underlying disease will provide best results. The ketogenic diet for patients with paroxysmal exertion-induced dyskinesias is a promising new therapeutic strategy and may not only prevent attacks but also lead to improvement of developmental delay in affected children.

A family with paroxysmal nonkinesigenic dyskinesia: genetic and treatment issues

Paroxysmal nonkinesigenic dyskinesia is a condition characterized by attacks of sudden involuntary movements triggered by caffeine or alcohol intake, stress, or fatigue. The paroxysms are usually of the generalized type and may last up to an hour. Described here is a Polish family with this disorder seen in two children and their father. Variable expressivity as well as reduced penetrance of the causative mutation were noteworthy in this kindred. Treatment options included abortive diazepam and prophylactic levetiracetam, with the latter having a more pronounced effect in this family. Favorable response to levetiracetam is probably linked to action of the drug on calcium channels in neurons, muscle cells, or both.

An inherited disorder characterized by repeated episodes of bilateral ballism: a case report

This case report describes two siblings with a dyskinetic form of cerebral palsy who had repeated episodes of fever-induced bilateral ballistic movements. The boy and his sister experienced the first episodes during early childhood. The movements developed over several hours and required rapid intervention. Electroencephalograms during the attacks showed no paroxysms, and brain magnetic resonance imaging scans revealed no lesions. The brother died of acute renal failure at age 5 due to rhabdomyolysis after his fifth episode of prolonged bilateral ballistic movements. This is the first report of an inherited disorder characterized by repeated episodes of violent movements.