Rapid onset dystonia-parkinsonism in a 14-year-old girl

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.

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.

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.

Two cases of autosomal recessive generalized dystonia in childhood: 5 year follow-up and bilateral globus pallidus stimulation results

We report two brothers with an unknown form of early-onset familiar dystonia. Characteristic clinical features are (1) childhood-onset; (2) extrapyramidal motor symptoms; (3) dysarthria; and (4) mental retardation. Additional findings include loss of D(2)-receptors in both basal ganglia and hypoplasia of the cerebellar vermis with dilatation of the fourth ventricle and cisterna magna. There seems to be a progressive and non-progressive form of this clinical entity. Dystonic symptoms of the progressive form that occurred in one of the brothers were alleviated dramatically by bilateral internal globus pallidus (Gpi) stimulation, and the improvement has lasted now for 5 years.

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

Rapid-onset dystonia-parkinsonism (RDP, DYT12, MIM 128235) is a rare autosomal dominant movement disorder characterized by abrupt onset of slow, dystonic movements and prominent bulbar features. Three families and 1 isolated case have been described in the literature, and linkage to markers on chromosome 19q13 have been reported. Here, we describe the clinical features in a fourth family (the second in Europe) with 4 affected members, suggesting that RDP may be misdiagnosed for years and/or may mimic other dystonic/parkinsonian syndromes. By using haplotype analysis, we show that the family is consistent with linkage to markers on chromosome 19q13.

Classification and genetics of dystonia

Dystonia is a syndrome characterised by sustained muscle contractions, producing twisting, repetitive, and patterned movements, or abnormal postures. The dystonic syndromes include a large group of diseases that have been classified into various aetiological categories, such as primary, dystonia-plus, heredodegenerative, and secondary. The diverse clinical features of these disorders are reflected in the traditional clinical classification based on age at onset, distribution of symptoms, and site of onset. However, with an increased awareness of the molecular and environmental causes, the classification schemes have changed to reflect different genetic forms of dystonia. To date, at least 13 dystonic syndromes have been distinguished on a genetic basis and their loci are referred to as DYT1 to DYT13. This review focuses on the molecular and phenotypic features of the hereditary dystonias, with emphasis on recent advances.

Possible sporadic rapid-onset dystonia-parkinsonism

Rapid-onset dystonia-parkinsonism is a hereditary disease characterized by a combination of dystonic and parkinsonian symptoms. Bulbar musculature is predominantly affected by dystonia. The onset is usually abrupt and the progression of the disease over years is minimal or absent. Homovanillic acid levels in cerebrospinal fluid can be diminished, suggesting that the pathogenesis of the disease is related to some dysfunction in dopaminergic neurotransmission. However, no abnormality has been found in positron emission tomography studies and levodopa does not improve symptoms. The genetic abnormality is not known, but evidence for linkage to markers on chromosome 19q13 has been reported. We describe the case of a woman with a clinical picture highly suggestive of rapid onset dystonia-parkinsonism (RDP) and no family history of the disease.

The genetics of primary dystonias and related disorders

Dystonias are a heterogeneous group of disorders which are known to have a strong inherited basis. This review details recent advances in our understanding of the genetic basis of dystonias, including the primary dystonias, the 'dystonia-plus' syndromes and heredodegenerative disorders. The review focuses particularly on clinical and genetic features and molecular mechanisms. Conditions discussed in detail include idiopathic torsion dystonia (DYT1), focal dystonias (DYT7) and mixed dystonias (DYT6 and DYT13), dopa-responsive dystonia, myoclonus dystonia, rapid-onset dystonia parkinsonism, Fahr disease, Aicardi-Goutieres syndrome, Hallervorden-Spatz syndrome, X-linked dystonia parkinsonism, deafness-dystonia syndrome, mitochondrial dystonias, neuroacanthocytosis and the paroxysmal dystonias/dyskinesias.