Rapid-onset dystonia-parkinsonism: A fourth family consistent with linkage to chromosome 19q13

ATP1A3 mutation in rapid-onset dystonia parkinsonism: New data and genotype-phenotype correlation analysis

Background

Rapid-onset dystonia parkinsonism (RDP) is a rare disease caused by ATP1A3 mutation with considerable clinical heterogeneity. Increased knowledge of RDP could be beneficial in its early diagnosis and treatment.

Objective

This study aimed to summarize the gene mutation spectrum of ATP1A3 associated with RDP, and to explore the correlation of ATP1A3 variants with RDP clinical phenotypes.

Methods

In this study, we reported two RDP patients from a family with a novel inherited ATP1A3 variant. Then, we reviewed and analyzed the available literature in English focused on ATP1A3-causative RDP. A total of 35 articles covering 15 families (59 patients) and 36 sporadic RDP cases were included in our analysis.

Results

The variant A813V (2438C>T) in ATP1A3 found in our cases was a novel mutant. Delays in diagnosis were common, with a mean delay time of 14 years. ATP1A3 had distinct RDP-related mutation hotspots, which consisted of exon8, 14, 17, and 18, and the most frequently occurring variants were T613M and I578S. Approximately 74.5% of patients have specific triggers before disease onset, and 82.1% of RDPs have stable symptoms within 1 month. The incidence rates of dystonia and bradykinesia are 100 and 88.1%, respectively. The onset site varied and exhibited a rostrocaudal gradient distribution pattern in 45% of patients with RDP. Approximately 63.6% of patients had mild improvement after receiving comprehensive interventions, especially in gait disturbance amelioration.

Conclusion

In patients with acute and unexplained dystonia or bradykinesia, gene screening on ATP1A3 should be timely performed. When a diagnosis has been made, treatments that may be effective are to be attempted. Our study would be helpful for the early diagnosis and treatment of ATP1T3-related RDP.

Cerebrospinal fluid biomarkers and genetic factors associated with normal pressure hydrocephalus and Alzheimer’s disease: a narrative review

Background

Normal pressure hydrocephalus is a neurologic disease leading to enlargement of ventricles which is presented with gait and balance disturbance, cognitive decline, and urinary incontinence. Diagnosis of normal pressure hydrocephalus is challenging due to the late onset of signs and symptoms. In this review, we summarize the cerebrospinal fluid, plasma, pathology, and genetic biomarkers of normal pressure hydrocephalus and related disorders.

Body

Recently, cerebrospinal fluid and serum biomarkers analysis alongside gene analysis has received a lot of attention. Interpreting a set of serum and cerebrospinal fluid biomarkers along with genetic testing for candidate genes could differentiate NPH from other neurological diseases such as Alzheimer's disease, Parkinson's disease with dementia, and other types of dementia.

Conclusion

Better understanding the pathophysiology of normal pressure hydrocephalus through genetic studies can aid in evolving preventative measures and the early treatment of normal pressure hydrocephalus patients.

Second hit hypothesis in dystonia: Dysfunctional cross talk between neuroplasticity and environment?

One of the great mysteries in dystonia pathophysiology is the role of environmental factors in disease onset and development. Progress has been made in defining the genetic components of dystonic syndromes, still the mechanisms behind the discrepant relationship between dystonic genotype and phenotype remain largely unclear. Within this review, the preclinical and clinical evidence for environmental stressors as disease modifiers in dystonia pathogenesis are summarized and critically evaluated. The potential role of extragenetic factors is discussed in monogenic as well as adult-onset isolated dystonia. The available clinical evidence for a "second hit" is analyzed in light of the reduced penetrance of monogenic dystonic syndromes and put into context with evidence from animal and cellular models. The contradictory studies on adult-onset dystonia are discussed in detail and backed up by evidence from animal models. Taken together, there is clear evidence of a gene-environment interaction in dystonia, which should be considered in the continued quest to unravel dystonia pathophysiology.

Oculogyric crises: A review of phenomenology, etiology, pathogenesis, and treatment

Oculogyric crises are a rare movement disorder characterized by paroxysmal, conjugate, tonic, usually upwards, deviation of the eyes. Causes for oculogyric crises are limited and include complications of dopamine-receptor blocking medications and neurometabolic disorders affecting dopamine metabolism, suggesting that an underlying hypodopaminergic state is important to the pathogenesis. Mimickers of oculogyric crises exist, and we propose diagnostic criteria to distinguish true oculogyric crises. Recognition of oculogyric crises is important for the diagnosis and appropriate treatment of rare disorders, and an approach to investigations in oculogyric crises is proposed. © 2017 International Parkinson and Movement Disorder Society.

A case of rapid-onset dystonia-parkinsonism accompanied by pyramidal tract impairment

BACKGROUND

Rapid-onset dystonia-parkinsonism (RDP) is a rare autosomal dominant disorder that is caused by mutations in the ATP1A3 gene and is characterized by an acute onset of asymmetric dystonia and parkinsonism. To date, fewer than 75 RDP cases have been reported worldwide. Clinical signs of pyramidal tract involvement have been reported in several RDP cases, and none of them included the Babinski sign.

CASE PRESENTATION

We report a 24-year-old Chinese female with RDP who exhibited a strikingly asymmetric, predominantly dystonic movement disorder with a rostrocaudal gradient of involvement and parkinsonism. Physical examiniations revealed hyperactive reflexes, bilateral ankle clonus and positive Babinski sign in the right. DTI showed reduced white matter integrity of the corticospinal tract in the frontal lobe and subpontine plane. Genetic testing revealed a missense mutation of the ATP1A3-gene (E277K) in the patient.

CONCLUSION

We suggest that pyramidal tract impairment could be involved in rapid-onset dystonia-parkinsonism and the pyramidal tract impairment in RDP needs to be differentiated from HSP.

Mosaicism in ATP1A3-related disorders: not just a theoretical risk

Mutations in ATP1A3 are involved in a large spectrum of neurological disorders, including rapid onset dystonia parkinsonism (RDP), alternating hemiplegia of childhood (AHC), and cerebellar ataxia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS), with recent descriptions of overlapping phenotypes. In AHC, a few familial cases of autosomal dominant inheritance have been reported, along with cases of de novo sporadic mutations. In contrast, autosomal dominant inheritance has frequently been associated with RDP and CAPOS. Here, we report on two unrelated sets of full siblings with ATP1A3 mutations, (c.2116G>A) p. Gly706Arg in the first family, and (c.2266C>T) p. Arg756Cys in the second family, presenting with familial recurrence of the disease. Both families displayed parental germline mosaicism. In the first family, the brother and sister presented with severe intellectual deficiency, early onset pharmacoresistant epilepsy, ataxia, and autistic features. In the second family, both sisters demonstrated severe encephalopathy with ataxia and dystonia following a regression episode during a febrile episode during infancy. To our knowledge, mosaicism has not previously been reported in ATP1A3-related disorders. This report, therefore, provides evidence that germline mosaicism for ATP1A3 mutations is a likely explanation for familial recurrence and should be considered during recurrence risk counseling for families of children with ATP1A3-related disorders.

Distinct neurological disorders with ATP1A3 mutations

Genetic research has shown that mutations that modify the protein-coding sequence of ATP1A3, the gene encoding the α3 subunit of Na(+)/K(+)-ATPase, cause both rapid-onset dystonia parkinsonism and alternating hemiplegia of childhood. These discoveries link two clinically distinct neurological diseases to the same gene, however, ATP1A3 mutations are, with one exception, disease-specific. Although the exact mechanism of how these mutations lead to disease is still unknown, much knowledge has been gained about functional consequences of ATP1A3 mutations using a range of in-vitro and animal model systems, and the role of Na(+)/K(+)-ATPases in the brain. Researchers and clinicians are attempting to further characterise neurological manifestations associated with mutations in ATP1A3, and to build on the existing molecular knowledge to understand how specific mutations can lead to different diseases.

Engineering animal models of dystonia

Dystonia is a neurological disorder characterized by abnormal involuntary movements that are prolonged and often cause twisting and turning. Several genetically modified worms, fruit flies, and rodents have been generated as models of genetic dystonias, in particular DYT1, DYT11, and DYT12 dystonias. Although these models do not show overt dystonic symptoms, the rodent models exhibit motor deficits in specialized behavioral tasks, such as the rotarod and beam-walking tests. For example, in a rodent model of DYT12 dystonia, which is generally stress triggered, motor deficits are observed only after the animal is stressed. Moreover, in a rodent model of DYT1 dystonia, the motor and electrophysiological deficits can be rescued by trihexyphenidyl, a common anticholinergic medication used to treat dystonic symptoms in human patients. Biochemically, the DYT1 and DYT11 animal models also share some similarities to patients, such as a reduction in striatal D2 dopamine receptor and binding activities. In addition, conditional knockout mouse models for DYT1 and DYT11 dystonia demonstrate that loss of the causal dystonia-related proteins in the striatum leads to motor deficits. Interestingly, loss of the DYT1 dystonia causal protein in Purkinje cells shows an improvement in motor performance, suggesting that gene therapy targeting of the cerebellum or intervention in its downstream pathways may be useful. Finally, recent studies using DYT1 dystonia worm and mouse models led to a potential novel therapeutic agent, which is currently undergoing clinical trials. These results indicate that genetic animal models are powerful tools to elucidate the pathophysiology and to further develop new therapeutics for dystonia.

Heterozygous de-novo mutations in ATP1A3 in patients with alternating hemiplegia of childhood: a whole-exome sequencing gene-identification study

BACKGROUND

Alternating hemiplegia of childhood (AHC) is a rare neurological disorder characterised by early-onset episodes of hemiplegia, dystonia, various paroxysmal symptoms, and developmental impairment. Almost all cases of AHC are sporadic but AHC concordance in monozygotic twins and dominant transmission in a family with a milder phenotype have been reported. Thus, we aimed to identify de-novo mutations associated with this disease.

METHODS

We recruited patients with clinically characterised AHC from paediatric neurology departments in Germany and with the aid of a parental support group between Sept, 2004, and May 18, 2012. We used whole-exome sequencing of three proband-parent trios to identify a disease-associated gene and then tested whether mutations in the gene were also present in the remaining patients and their healthy parents. We analysed genotypes and characterised their associations with the phenotypic spectrum of the disease.

FINDINGS

We studied 15 female and nine male patients with AHC who were aged 8-35 years. ATP1A3 emerged as the disease-associated gene in AHC. Whole-exome sequencing showed three heterozygous de-novo missense mutations. Sequencing of the 21 remaining affected individuals identified disease-associated mutations in ATP1A3 in all patients, including six de-novo missense mutations and one de-novo splice-site mutation. Because ATP1A3 is also the gene associated with rapid-onset dystonia-parkinsonism (DYT12, OMIM 128235) we compared the genotypes and phenotypes of patients with AHC in our cohort with those of patients with rapid-onset dystonia-parkinsonism reported in the scientific literature. We noted overlapping clinical features, such as abrupt onset of dystonic episodes often triggered by emotional stress, a rostrocaudal (face to arm to leg) gradient of involvement, and signs of brainstem dysfunction, as well as clearly differentiating clinical characteristics, such as episodic hemiplegia and quadriplegia.

INTERPRETATION

Mutation analysis of the ATP1A3 gene in patients who met clinical criteria for AHC allows for definite genetic diagnosis and sound genetic counselling. AHC and rapid-onset dystonia-parkinsonism are allelic diseases related to mutations in ATP1A3 and form a phenotypical continuum of a dystonic movement disorder.

FUNDING

Eva Luise and Horst Köhler Foundation for Humans with Rare Diseases.

New triggers and non-motor findings in a family with rapid-onset dystonia-parkinsonism

BACKGROUND

A woman from Italy presented with dystonic leg symptoms at the age of 59. Rapid-onset dystonia-parkinsonism (RDP) was not suspected until 3 affected children (2 male, 1 female) with presentations consistent with the disorder were recognized.

METHODS

The mother and four of her children (3 with and 1 without dystonia) were evaluated with an extensive battery including standardized history questionnaire and rating scales. In addition, all four children had cognitive testing and three of the four children had psychiatric interviews.

RESULTS

In this family, a T613M mutation in the ATP1A3 gene was confirmed, the most common mutation present in patients with RDP. The proband's limb dystonia was atypical of RDP, symptoms of the others affected included dysarthria, asymmetric limb dystonia, and dysphagia more consistent with RDP. The two sons developed dystonia-parkinsonism in adolescence after consuming large amounts of alcohol. All 3 of those with psychiatric interviews reached diagnosable thresholds for mood disorder (bipolar or dysthymia) and some form of anxiety disorder.

CONCLUSIONS

The phenotype and age of onset is broader than previously reported in RDP, suggesting that it could be under-reported. Prior to this study, neuropsychologic symptoms associated with RDP were under-appreciated. Those patients who are at risk or suspected of having RDP should be cautioned to avoid excessive alcohol intake. Further study is needed to assess if the cognitive and psychiatric features are part of a broader RDP phenotype and this may have implications for future research into genetic susceptibility for psychiatric disease.

Migraine- and dystonia-related disease-mutations of Na+/K+-ATPases: relevance of behavioral studies in mice to disease symptoms and neurological manifestations in humans

The two autosomal dominantly inherited neurological diseases: familial hemiplegic migraine type 2 (FHM2) and familial rapid-onset of dystonia-parkinsonism (Familial RDP) are caused by in vivo mutations of specific alpha subunits of the sodium-potassium pump (Na(+)/K(+)-ATPase). Intriguingly, patients with classical FHM2 and RDP symptoms additionally suffer from other manifestations, such as epilepsy/seizures and developmental disabilities. Recent studies of FHM2 and RDP mouse models provide valuable tools for dissecting the vital roles of the Na(+)/K(+)-ATPases, and we discuss their relevance to the complex patient symptoms and manifestations. Thus, it is interesting that mouse models targeting a specific α-isoform cause different, although still comparable, phenotypes consistent with classical symptoms and other manifestations observed in FHM2 and RDP patients. This review highlights that use of mouse models have broad potentials for future research concerning migraine and dystonia-related diseases, which will contribute towards understanding the, yet unknown, pathophysiologies.

Milestones in dystonia

The last 25 years have seen remarkable advances in our understanding of the genetic etiologies of dystonia, new approaches into dissecting underlying pathophysiology, and independent progress in identifying effective treatments. In this review we highlight some of these advances, especially the genetic findings that have taken us from phenomenological to molecular-based diagnoses. Twenty DYT loci have been designated and 10 genes identified, all based on linkage analyses in families. Hand in hand with these genetic findings, neurophysiological and imaging techniques have been employed that have helped illuminate the similarities and differences among the various etiological dystonia subtypes. This knowledge is just beginning to yield new approaches to treatment including those based on DYT1 animal models. Despite the lag in identifying genetically based therapies, effective treatments, including impressive benefits from deep brain stimulation and botulinum toxin chemodenervation, have marked the last 25 years. The challenge ahead includes continued advancement into understanding dystonia's many underlying causes and associated pathology and using this knowledge to advance treatment including preventing genetic disease expression.

Rapid-onset dystonia-parkinsonism

Rapid-onset dystonia-parkinsonism (RDP) is a rare condition with autosomal-dominant inheritance causing dystonia and parkinsonism which develop over a short period of time. It results from abnormalities in the Na(+)/K(+)-ATPase pump due to mutations in the ATP1A3 gene. This chapter reviews the clinical features, genetics, and diagnosis of this disorder.

Characterization of Atp1a3 mutant mice as a model of rapid-onset dystonia with parkinsonism

Rapid-onset dystonia with parkinsonism (RDP) or DYT12 dystonia is a rare form of primary, generalized dystonia. Patients do not present with any symptoms until triggered by a physiological stressor. Within days, patients will show both dystonia and parkinsonism. Mutations resulting in a loss of function in the ATP1A3 gene have been identified as the cause of RDP. ATP1A3 encodes the α3 subunit of the Na(+)/K(+)-ATPase, which is exclusively expressed in neurons and cardiac cells. We have previously created a line of mice harboring a point mutation of the Atp1a3 gene (mouse homolog of the human ATP1A3 gene) that results in a loss of function of the α3 subunit. The Atp1a3 mutant mice showed hyperactivity, spatial learning and memory deficits, and increased locomotion induced by methamphetamine. However, the full spectrum of the motor phenotype has not been characterized in the mutant mice and it is not known whether triggers such as restraint stress affect the motor phenotype. Here, we characterized the motor phenotype in normal heterozygous Atp1a3 mutant mice and heterozygous Atp1a3 mutant mice that have been exposed to a restraint stress. We found that this type of trigger induced significant deficits in motor coordination and balance in the mutant mice, characteristic of other genotypic dystonia mouse models. Furthermore, stressed mutant mice also had a decreased thermal sensitivity and alterations in monoamine metabolism. These results suggest that the Atp1a3 mutant mouse models several characteristics of RDP and further analysis of this mouse model will provide great insight into pathogenesis of RDP.

[123I]-FP-CIT and [99mTc]-HMPAO single photon emission computed tomography in a new sporadic case of rapid-onset dystonia-parkinsonism

Rapid-onset dystonia-parkinsonism (RDP) is a rare, autosomal-dominantly inherited syndrome characterized by abrupt onset, over hours to days, of dystonic and parkinsonian symptoms. To date, RDP has been described in a small number of families, and in only four sporadic cases.

METHODS

We here report a new sporadic case of RDP who has a novel de novo mutation in the ATP1A3 gene. Striatal dopamine transporters have been assessed quantitatively using [123I]-FP-CIT SPECT. A volume of interest (VOI) was drawn within the occipital cortex to obtain non-specific activity and specific to non-specific binding ratios (BR) were calculated. A single template of predefined VOI 3D-drawn on right and left caudate nucleus and putamen was applied to the spatially normalized BR images. BR values were compared to those obtained from an age-matched control group and from a group of patients suffering from Parkinson's disease (Hoehn and Yahr score 2 or 3). A [99mTc]-HMPAO cerebral blood flow study was also performed.

RESULTS

In the control group, BR values (mean+/-Standard Deviation) were 3.5+/-0.4 for the left striatum and 3.3+/-0.3 for the right one. RDP patient's values were 3 and 2.7, respectively. In the Parkinson group, values were 1.6+/-0.3 and 1.7+/-0.4, respectively. [99mTc]-HMPAO scan showed homogeneous cortical and sub-cortical perfusion.

CONCLUSION

Quantification of striatal [123I]-FP-CIT uptake in a new sporadic case of RDP with a novel mutation in the ATP1A3 gene showed values just within the range of normality. [99mTc]-HMPAO scan was normal.

ATP1A3 mutation in the first asian case of rapid-onset dystonia-parkinsonism

We report a 38-year-old Korean man with sporadic rapid-onset dystonia-parkinsonism (RDP), who had a Thr 618 Met mutation in the Na(+)/K(+)-ATPase alpha3 subunit gene (ATP1A3). At the age of 21, he acutely developed severe dystonia and parkinsonism, which rapidly deteriorated into a wheelchair-bound state within 4 days. He is the first Asian RDP patient confirmed by genetic testing, ascertaining that RDP gene mutation is present in Asians. Pathophysiological considerations are briefly discussed.

The phenotypic spectrum of rapid-onset dystonia-parkinsonism (RDP) and mutations in the ATP1A3 gene

Rapid-onset dystonia-parkinsonism (RDP) (also known as DYT12) is characterized by the abrupt onset of dystonia and parkinsonism and is caused by mutations in the ATP1A3 gene. We obtained clinical data and sequenced the ATP1A3 gene in 49 subjects from 21 families referred with 'possible' RDP, and performed a genotype-phenotype analysis. Of the new families referred for study only 3 of 14 families (21%) demonstrated a mutation in the ATP1A3 gene, but no new mutations were identified beyond our earlier report of 6. Adding these to previously reported families, we found mutations in 36 individuals from 10 families including 4 de novo mutations and excluded mutations in 13 individuals from 11 families. The phenotype in mutation positive patients included abrupt onset of dystonia with features of parkinsonism, a rostrocaudal gradient, and prominent bulbar findings. Other features found in some mutation carriers included common reports of triggers, minimal or no tremor at onset, occasional mild limb dystonia before the primary onset, lack of response to dopaminergic medications, rare abrupt worsening of symptoms later in life, stabilization of symptoms within a month and minimal improvement overall. In comparing ATP1A3 mutation positive and negative patients, we found that tremor at onset of symptoms, a reversed rostrocaudal gradient, and significant limb pain exclude a diagnosis of RDP. A positive family history is not required. Genetic testing for the ATP1A3 gene is recommended when abrupt onset, rostrocaudal gradient and prominent bulbar findings are present.

Heterogeneity of presentation and outcome in the Irish rapid-onset dystonia–Parkinsonism kindred

The authors report a 7-year follow-up video study and molecular data on the Irish rapid-onset dystonia-Parkinsonism kindred. All affected patients tested had a missense mutation in the Na(+)/K(+) -ATPase alpha3 subunit (ATP1A3), twice previously identified, suggestive of a mutation hotspot. Clinical presentation, progression, and outcome in this kindred is varied. Some patients remain stable over many years, others worsen, have a fluctuating course, or improve over time. To date there have been no effective treatments for this disorder, although Na(+)/K(+) ATPase may be a future therapeutic target. The broad phenotypic spectrum of RDP described in the text and detailed in the video, should be considered when evaluating patients with dystonia.

Sporadic rapid-onset dystonia-parkinsonism presenting as Parkinson's disease

We report on a 38-year-old patient with rapid-onset dystonia-parkinsonism (RDP) with a missense mutation in the Na/K-ATPase alpha3 subunit (ATP1A3). Asymmetrical parkinsonian symptoms evolved over a year. After a stable episode of another 2.5 years, overnight he developed oromandibular dystonia and more severe parkinsonian symptoms. We conclude that RDP should be considered as a rare cause of levodopa-unresponsive parkinsonism even if there is no family history and the classic presentation is lacking.