Neuroacanthocytosis Research Articles

Chapter 27 - Trinucleotide repeat disorders

Trinucleotide repeat disorders comprise a variable group of inherited neurodegenerative diseases, with a large range in prevalence figures. There is a broad range in clinical presentations, but many of these diseases lead to some form of ataxia or other movement disorders, which are frequently combined with cognitive or psychiatric disturbances. This group can be divided into CAG- versus non-CAG-repeat diseases. Apart from spinocerebellar ataxia type 6 and 12 (SCA6 and SCA12), these CAG-repeat diseases, as well as Huntington disease-like 2 (HDL2) and SCA8, can be neuropathologically identified using 1C2 polyglutamine antibodies. In fragile X-associated tremor and ataxia, SCA6 and SCA12 ubiquitin/p62-positive and 1C2-negative inclusion bodies can be observed. In the other diseases proteinaceous inclusions are not found. For definite diagnosis genetic analysis is necessary.

Update on chorea

Chorea is a movement disorder characterized by a continuous flow of unpredictable muscle contractions conveying a dance-like appearance. The aim of this talk is to provide an overview of new developments in the field of chorea. There is an ongoing phase 1 trial of ISIS-HTTRX, an antisense oligonucleotide aiming at reducing the expression of huntingtin in Huntington’s disease (HD). HD is the most common cause of genetic choreas. HD phenocopies are patients with the phenotype of the disease but without the genetic defect of HD. Expansion of the C9orf72 hexanucleotide is the most common cause of phenocopies among Caucasians whereas Huntington disease like-2 mutation is the leading cause in areas with significant African background. Benign hereditary chorea (BHC), the most common etiology of genetic chorea in children, is usually caused by mutations of the NKX2-1 (TITF1). There is growing recognition though that BHC phenotype can be associated with mutations of the ADCY5 gene. The usual clinical features of the later are a variable combination of facial dyskinesia, dystonia, pyramidal signs and cognitive impairment with a characteristic worsening during induction of sleep. Vascular disease remains as the most common cause of acquired chorea in adults whereas Sydenham’s chorea (SC) account for the vast majority of cases in children. There has been a steep decline of the incidence of SC even in the developing world. In contrast, several new auto-immune causes of chorea have been recently described. Anti-NMDAR encephalitis causes a complex movement disorders that can include chorea. A few patients with anti-LGI1 antibody, a condition more commonly seen in elderly people, may have chorea as part of their clinical picture.

A Systematic Review of the Huntington Disease-Like 2 Phenotype.

Huntington Disease-like 2 (HDL2) is a neurodegenerative disorder similar to Huntington Disease (HD) in its clinical phenotype, genetic characteristics, neuropathology and longitudinal progression. Proposed specific differences include an exclusive African ancestry, lack of eye movement abnormalities, increased Parkinsonism, and acanthocytes in HDL2. The objective was to determine the similarities and differences between HD and HDL2 by establishing the clinical phenotype of HDL2 with the published cases. A literature review of all clinically described cases of HDL2 until the end of 2016 was performed and a descriptive analysis was carried out. Sixty-nine new cases were described between 2001 and 2016. All cases had likely African ancestry, and most were found in South Africa and the USA. Many features were found to be similar to HD, including a strong negative correlation between repeat length and age of onset. Chorea was noted in 48/57 cases (84%). Dementia was reported in 74% patients, and Parkinsonism in 37%. Psychiatric features were reported in 44 out of 47 cases. Patients with chorea had lower expanded repeat lengths compared to patients without chorea. Eye movements were described in 19 cases, 8 were abnormal. Acanthocytes were detected in 4 of the 13 patients tested. Nineteen out of 20 MRIs were reported as abnormal with findings similar to HD. This review clarifies some aspects of the HDL2 phenotype and highlights others which require further investigation. Features that are unique to HDL2 have been documented in a minority of subjects and require prospective validation.

Pathogenic insights from Huntington's disease-like 2 and other Huntington's disease genocopies.

Huntington's disease-like 2 (HDL2) is a rare, progressive, autosomal dominant neurodegenerative disorder that genetically, clinically, and pathologically closely resembles Huntington's disease. We review HDL2 pathogenic mechanisms and examine the implications of these mechanisms for Huntington's disease and related diseases. HDL2 is caused by a CTG/CAG repeat expansion in junctophilin-3. Available data from cell and animal models and human brain suggest that HDL2 is a complex disease in which transcripts and proteins expressed bidirectionally from the junctophilin-3 locus contribute to pathogenesis through both gain-and loss-of-function mechanisms. Recent advances indicate that the pathogenesis of Huntington's disease is equally complex, despite the emphasis on toxic gain-of-function properties of the mutant huntingtin protein. Studies examining in parallel the genetic, clinical, neuropathological, and mechanistic similarities between Huntington's disease and HDL2 have begun to identify points of convergence between the pathogenic pathways of the two diseases. Comparisons to other diseases that are phenotypically or genetically related to Huntington's disease and HDL2 will likely reveal additional common pathways. The ultimate goal is to identify shared therapeutic targets and eventually develop therapies that may, at least in part, be effective across multiple similar rare diseases, an essential approach given the scarcity of resources for basic and translational research.

Quantitative Proteomic Analysis Reveals Similarities between Huntington's Disease (HD) and Huntington's Disease-Like 2 (HDL2) Human Brains.

The pathogenesis of HD and HDL2, similar progressive neurodegenerative disorders caused by expansion mutations, remains incompletely understood. No systematic quantitative proteomics studies, assessing global changes in HD or HDL2 human brain, were reported. To address this deficit, we used a stable isotope labeling-based approach to quantify the changes in protein abundances in the cortex of 12 HD and 12 control cases and, separately, of 6 HDL2 and 6 control cases. The quality of the tissues was assessed to minimize variability due to post mortem autolysis. We applied a robust median sweep algorithm to quantify protein abundance and performed statistical inference using moderated test statistics. 1211 proteins showed statistically significant fold changes between HD and control tissues; the differences in selected proteins were verified by Western blotting. Differentially abundant proteins were enriched in cellular pathways previously implicated in HD, including Rho-mediated, actin cytoskeleton and integrin signaling, mitochondrial dysfunction, endocytosis, axonal guidance, DNA/RNA processing, and protein transport. The abundance of 717 proteins significantly differed between control and HDL2 brain. Comparative analysis of the disease-associated changes in the HD and HDL2 proteomes revealed that similar pathways were altered, suggesting the commonality of pathogenesis between the two disorders.

A Drosophila model of Huntington disease-like 2 exhibits nuclear toxicity and distinct pathogenic mechanisms from Huntington disease.

Huntington disease-like 2 (HDL2) and Huntington disease (HD) are adult-onset neurodegenerative diseases characterized by movement disorders, psychiatric disturbances and cognitive decline. Brain tissue from HD and HDL2 patients shows degeneration of the striatum and ubiquitinated inclusions immunoreactive for polyglutamine (polyQ) antibodies. Despite these similarities, the diseases result from different genetic mutations. HD is caused by a CAG repeat expansion in the huntingtin (HTT) gene, while HDL2 results from an expansion at the junctophilin 3 (JPH3) locus. Recent evidence indicates that the HDL2 expansion may give rise to a toxic polyQ protein translated from an antisense mRNA derived from the JPH3 locus. To investigate this hypothesis, we generated and characterized a Drosophila HDL2 model and compared it with a previously established HD model. We find that neuronal expression of HDL2-Q15 is not toxic, while the expression of an expanded HDL2-Q138 protein is lethal. HDL2-Q138 forms large nuclear aggregates, with only smaller puncta observed in the cytoplasm. This is in contrast to what is observed in a Drosophila model of HD, where polyQ aggregates localize exclusively to the cytoplasm. Altering localization of HLD2 with the addition of a nuclear localization or nuclear export sequence demonstrates that nuclear accumulation is required for toxicity in the Drosophila HDL2 model. Directing HDL2-Q138 to the nucleus exacerbates toxicity in multiple tissue types, while confining HDL2-Q138 to the cytoplasm restores viability to control levels. We conclude that while HD and HDL2 have similar clinical profiles, distinct pathogenic mechanisms are likely to drive toxicity in Drosophila models of these disorders.

Management of Neuroacanthocytosis Syndromes.

BackgroundThe two core neuroacanthocytosis (NA) syndromes, chorea-acanthocytosis (ChAc) and McLeod syndrome, are progressive neurodegenerative disorders that primarily affect the basal ganglia. The characteristic phenotype comprises a variety of movement disorders including chorea, dystonia, and parkinsonism, as well as psychiatric and cognitive symptoms attributable to basal ganglia dysfunction. These disorders are symptomatically managed on a case-by-case basis, with very few practitioners seeing more than a single case in their careers.MethodsA literature search was performed on PubMed utilizing the terms neuroacanthocytosis, chorea-acanthocytosis, and McLeod syndrome, and articles were reviewed for mentions of therapies, successful or otherwise.ResultsThere have been no blinded, controlled trials and only one retrospective case series describing ChAc. The various therapies that have been used in patients with NA syndromes are summarized.DiscussionManagement remains at present purely symptomatic, which is similar in principle to other more common basal ganglia neurodegenerative disorders such as Huntington’s disease (HD) and Parkinson’s disease (PD). However, there are some specific issues particular to NA syndromes that merit attention. An integrated multidisciplinary approach is the ideal management strategy for these complex and multifaceted neurodegenerative disorders.

Neuroacanthocytosis: Observations, Theories and Perspectives on the Origin and Significance of Acanthocytes.

The presence of acanthocytes in the blood is characteristic of patients suffering from neuroacanthocytosis (NA). Recent studies have described abnormal phosphorylation of the proteins involved in connecting the membrane and cytoskeleton in patient-derived erythrocytes. The involvement of lipids in the underlying signaling pathways and recent reports on in vitro disease-associated lipid alterations support renewed research into lipid composition, signal transduction, and metabolism in patient erythrocytes. In addition to morphology, changes in membrane organization affect erythrocyte function and survival. Patient erythrocytes may have a decreased ability to deform, and this may contribute to accelerated erythrocyte removal and a decreased oxygen supply, especially in vulnerable brain regions. The presently available data indicate that acanthocytes are likely to originate in the bone marrow, making erythropoiesis an obvious new focus in NA research. Moreover, new, detailed morphological observations indicate that acanthocytes may be the tip of the iceberg with regard to misshapen erythrocytes in the circulation of patients with NA.A systematic assessment of patient erythrocyte morphology, deformability, oxygen delivery, and metabolism will be instrumental in determining the putative contribution of erythrocyte function to NA clinical symptoms.

Neuroacanthocytosis: Observations, Theories and Perspectives on the Origin and Significance of Acanthocytes

Neuroacanthocytosis: Observations, Theories and Perspectives on the Origin and Significance of Acanthocytes

Junctophilin 3 (JPH3) expansion mutations causing Huntington disease like 2 (HDL2) are common in South African patients with African ancestry and a Huntington disease phenotype.

Huntington disease (HD) is a progressive autosomal dominant neurodegenerative disorder, characterized by abnormal movements, cognitive decline, and psychiatric symptoms, caused by a CAG repeat expansion in the huntingtin (HTT) gene on chromosome 4p. A CAG/CTG repeat expansion in the junctophilin-3 (JPH3) gene on chromosome 16q24.2 causes a Huntington disease-like phenotype (HDL2). All patients to date with HDL2 have some African ancestry. The present study aimed to characterize the genetic basis of the Huntington disease phenotype in South Africans and to investigate the possible origin of the JPH3 mutation. In a sample of unrelated South African individuals referred for diagnostic HD testing, 62% (106/171) of white patients compared to only 36% (47/130) of black patients had an expansion in HTT. However, 15% (20/130) of black South African patients and no white patients (0/171) had an expansion in JPH3, confirming the diagnosis of Huntington disease like 2 (HDL2). Individuals with HDL2 share many clinical features with individuals with HD and are clinically indistinguishable in many cases, although the average age of onset and diagnosis in HDL2 is 5 years later than HD and individual clinical features may be more prominent. HDL2 mutations contribute significantly to the HD phenotype in South Africans with African ancestry. JPH3 haplotype studies in 31 families, mainly from South Africa and North America, provide evidence for a founder mutation and support a common African origin for all HDL2 patients. Molecular testing in individuals with an HD phenotype and African ancestry should include testing routinely for JPH3 mutations.

Abnormal red cell structure and function in neuroacanthocytosis.

BackgroundPanthothenate kinase-associated neurodegeneration (PKAN) belongs to a group of hereditary neurodegenerative disorders known as neuroacanthocytosis (NA). This genetically heterogeneous group of diseases is characterized by degeneration of neurons in the basal ganglia and by the presence of deformed red blood cells with thorny protrusions, acanthocytes, in the circulation.ObjectiveThe goal of our study is to elucidate the molecular mechanisms underlying this aberrant red cell morphology and the corresponding functional consequences. This could shed light on the etiology of the neurodegeneration.MethodsWe performed a qualitative and semi-quantitative morphological, immunofluorescent, biochemical and functional analysis of the red cells of several patients with PKAN and, for the first time, of the red cells of their family members.ResultsWe show that the blood of patients with PKAN contains not only variable numbers of acanthocytes, but also a wide range of other misshapen red cells. Immunofluorescent and immunoblot analyses suggest an altered membrane organization, rather than quantitative changes in protein expression. Strikingly, these changes are not limited to the red blood cells of PKAN patients, but are also present in the red cells of heterozygous carriers without neurological problems. Furthermore, changes are not only present in acanthocytes, but also in other red cells, including discocytes. The patients’ cells, however, are more fragile, as observed in a spleen-mimicking device.ConclusionThese morphological, molecular and functional characteristics of red cells in patients with PKAN and their family members offer new tools for diagnosis and present a window into the pathophysiology of neuroacanthocytosis.

Untangling the Thorns: Advances in the Neuroacanthocytosis Syndromes

There have been significant advances in neuroacanthocytosis (NA) syndromes in the past 20 years, however, confusion still exists regarding the precise nature of these disorders and the correct nomenclature. This article seeks to clarify these issues and to summarise the recent literature in the field. The four key NA syndromes are described here–chorea-acanthocytosis, McLeod syndrome, Huntington’s disease-like 2, and pantothenate kinase- associated neurodegeneration. In the first two, acanthocytosis is a frequent, although not invariable, finding; in the second two, it occurs in approximately 10% of patients. Degeneration affecting the basal ganglia is the key neuropathologic finding, thus the clinical presentations can be remarkably similar. The characteristic phenotype comprises a variety of movement disorders, including chorea, dystonia, and parkinsonism, and also psychiatric and cognitive symptoms attributable to basal ganglia dysfunction. The age of onset, inheritance patterns, and ethnic background differ in each condition, providing diagnostic clues. Other investigations, including routine blood testing and neuroimaging can be informative. Genetic diagnosis, if available, provides a definitive diagnosis, and is important for genetic counseling, and hopefully molecular therapies in the future. In this article I provide a historical perspective on each NA syndrome. The first 3 disorders, chorea-acanthocytosis, McLeod syndrome, Huntington’s disease-like 2, are discussed in detail, with a comprehensive review of the literature to date for each, while pantothenate kinase-associated neurodegeneration is presented in summary, as this disorder has recently been reviewed in this journal. Therapy for all of these diseases is, at present, purely symptomatic.

Acanthocytosis and the c.680 A>G Mutation in the PANK2 Gene: A Study Enrolling a Cohort of PKAN Patients from the Dominican Republic.

Pantothenate Kinase-Associated Neurodegeneration (PKAN) is a form of Neurodegeneration with Brain Iron Accumulation (NBIA) associated with mutations in the pantothenate kinase 2 gene (PANK2). Pantothenate kinases catalyze the rate-limiting step of coenzyme A synthesis and Pank2 is the only pantothenate kinase isoform in humans that is localized to mitochondria. Acanthocytosis, the occurrence of spiculated erythrocytes, is observed in about 10% of the PKAN patients. Therefore PKAN is also classified together with other rare neurodegenerative diseases like Chorea Acanthocytosis (ChAc) and McLeod syndrome (MLS) into the Neuroacanthocytosis (NA) syndromes. It has not been investigated yet whether acanthocytosis in PKAN is associated with a specific subset of Pank2 mutations. In this study, we analyzed acanthocytosis of a cohort of 25 PKAN patients from the Dominican Republic that are homozygous for the c.680 A>G mutation in the PANK2 gene as compared to control donors that are heterozygous or wild-type with respect to this mutation. 3D modeling of this mutation indicated that the replacement of a tyrosine by a cysteine at position 227 in Pank2 disrupts a polar interaction within the A domain of the enzyme. Mean acanthocyte count was elevated in the cohort of patients, however, acanthocytosis varied among the patients with nearly half of them showing high (>20%) or elevated acanthocytosis and the rest showing mild (6-10%) or no (<6%) acanthocytosis. Heterozygous control donors revealed a tendency to mild acanthocytosis. Based on the insight that Pank2 is a normal constituent of red blood cells and de novo biosynthesis of coenzyme A is likely to take place in the erythrocyte cytosol we propose a hypothetical model that accounts for the variability in the occurrence of acanthocytic cells in PKAN.

Neuroacanthocytosis in a psychiatry clinic: a case report

Neuroacanthocytosis (NA) syndromes are a group of genetically defined diseases characterized by peripheral blood acanthocytes, central nervous system as well as neuromuscular symptoms. The clinical presentation of neuroacanthocytosis typically includes chorea and dystonia. Psychiatric and cognitive symptoms may be significant including obsessive–compulsive disorder, depression and schizophrenia-like psychosis (1,2). Here, we aim to discuss a case presented with psychiatric symptoms and orofacial dyskinesia with the diagnosis of neuroacanthocytosis.A 25 year-old man was admitted to our outpatient clinic with depression, tongue biting and a speech disorder alleviated. His symptoms began after the death of his mother one year ago. Psychiatric examination showed that he had depression childish speaking as well as behavioral abnormalities. His history revealed dependent personality disorder. Neurological examination showed chorea, tics in his face and arms and hypotonia in all extremities. His cranial magnetic resonance imaging was normal (Photo), muscle enzymes were elevated, peripheral blood smear showed increased number of acanthocytes. The differential diagnosis was made between chorea-acanthocytosis, McLeod's syndrome and Huntington's disease. The gene analysis for Huntington’s disease was negative, his lipid profile was normal. Symptomatic treatment was commenced.

Proceedings of the third joint symposium on neuroacanthocytosis and neurodegeneration with brain iron accumulation: from benchside to bedside.

Proceedings of the third joint symposium on neuroacanthocytosis and neurodegeneration with brain iron accumulation: from benchside to bedside.

Neuroacanthocytosis in China: A Review of Published Reports

<strong>Background:</strong> Neuroacanthocytosis (NA) syndromes are a group of rare diseases characterized by the presence of acanthocytes and neuronal multisystem pathology, including chorea-acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington’s disease-like 2 (HDL-2), and pantothenate kinase-associated neurodegeneration (PKAN). China has the largest population in the world, which makes it a good location for investigating rare diseases like NA. <strong>Methods:</strong> We searched Medline, ISI Proceedings, China National Knowledge Infrastructure, and Wanfang Data for literature published through December 31, 2013 for all the published Chinese NA case reports and extracted the clinical and laboratory findings. <strong>Results:</strong> A total of 42 studies describing 66 cases were found to be eligible for inclusion. Age of symptom onset ranged from 5 to 74 years. The most common findings included hyperkinetic movements (88%), orofacial dyskinesia (80%), dystonia (67%), and dysarthria (68%), as well as caudate atrophy or enlarged lateral ventricles on neuroimaging (64%), and elevated creatine kinase (52%). Most cases were not confirmed by any specific molecular tests. Only two cases were genetically studied and diagnosed as ChAc or MLS. <strong>Discussion:</strong> In view of the prevalence of NA syndromes in other countries, the number of patients in China appears to be underestimated. Chinese NA patients may benefit from the establishment of networks that offer specific diagnoses and care for rare diseases.

Neuroacanthocytosis in china: a review of published reports.

BackgroundNeuroacanthocytosis (NA) syndromes are a group of rare diseases characterized by the presence of acanthocytes and neuronal multisystem pathology, including chorea-acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington's disease-like 2 (HDL-2), and pantothenate kinase-associated neurodegeneration (PKAN). China has the largest population in the world, which makes it a good location for investigating rare diseases like NA.MethodsWe searched Medline, ISI Proceedings, China National Knowledge Infrastructure, and Wanfang Data for literature published through December 31, 2013 for all the published Chinese NA case reports and extracted the clinical and laboratory findings.ResultsA total of 42 studies describing 66 cases were found to be eligible for inclusion. Age of symptom onset ranged from 5 to 74 years. The most common findings included hyperkinetic movements (88%), orofacial dyskinesia (80%), dystonia (67%), and dysarthria (68%), as well as caudate atrophy or enlarged lateral ventricles on neuroimaging (64%), and elevated creatine kinase (52%). Most cases were not confirmed by any specific molecular tests. Only two cases were genetically studied and diagnosed as ChAc or MLS.DiscussionIn view of the prevalence of NA syndromes in other countries, the number of patients in China appears to be underestimated. Chinese NA patients may benefit from the establishment of networks that offer specific diagnoses and care for rare diseases.

Alterations of Red Cell Membrane Properties in Nneuroacanthocytosis

Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington’s disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an “acanthocytic state” of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration.

Feeding dystonia: A classical presentation of neuroacanthocytosis

Introduction: Neuroacanthocytosis (NA) is a heterogeneous neurodegenerative genetic disorder caused by disease specific genetic mutation. Being an extremely rare disorder, only a few thousand cases have been reported till date. This clinical entity was described by Citchley et al. and was initially named Levine-Citchley syndrome. It is characterized by movement disorder due to degeneration of the basal ganglia along with cognitive and behavior changes. The classical clinical presentation includes the troublesome abnormal involuntary movements in form of chorea, dystonia and dyskinesia. Self mutilation of the lips and tongue is characteristic of choreoacanthocytosis. The NA syndromes have been broadly divided into two subtypes, (i) core NA syndromes, and (ii) conditions with alterations in the lipoprotein metabolism. The genes of the different NA syndromes have been identified but the mechanism of these genetic mutations is not known. The management of NA is primarily symptomatic and rehabilitative. Case Report: We are describing a case of neuroacanthocytosis with typical phenotype of choreoacanthocytosis. The phenomenon of feeding dystonia is classically being discussed in this report. Neuroimaging demonstrated the atrophy of the caudate nucleus resembling Huntington's chorea. Acanthocytic red blood cells were seen in peripheral smear in our patients. Conclusion: The recognition of neuroacanthocytosis is improved due to better characterization of the clinical symptoms and investigations of this heterogeneous entity. The presented case describes the typical clinical characteristics and investigations supporting the diagnosis of this under diagnosed clinical syndrome.

Huntington disease-like 2 (HDL2) in Venezuela: frequency and ethnic origin

Huntington disease (HD) phenotypes without a HTT mutation are known as HD-like (HDL) syndromes and are caused by mutations in other loci. HDL2, almost indistinguishable from HD, is due to expansions in the Junctophilin 3 locus (JPH3) with a worldwide Sub-Saharan ethnic origin. Sixteen independent patients with involuntary movements, psychiatric disturbances and ataxia not having a HTT mutation were searched for loci PRNP (prion protein, HDL1), JPH3 (HDL2), ATN1 (dentatorubral-pallidoluysian atrophy), ATX2 (spinocerebellar ataxia 2) ATXN3 (spinocerebellar ataxia 3), and TBP (spinocerebellar ataxia 17=HDL4). Markers Duffy, Kell, Diego, D9S1120, plus six JPH3 intragenic single-nucleotide polymorphisms were tested to ascertain ethnic origin. Four unrelated choreic patients had an expanded allele at JPH3. Three of them carried the African marker Duffy null. All four families carried with the mutation the same haplotype most frequent in African populations; Amerindian alleles D9D1120*9 and Diego A; or Kell allele K were absent. HDL2 in Venezuela had a low, but higher relative frequency (2.6%) than that in other Caucasoid populations. It should be searched first in choreic patients not having HTT mutations. The most likely remote ethnic origin for all detected families was African.