Prevalence of triplet repeat expansion in ataxia patients from Hokkaido, the northernmost island of Japan

Prevalence and Diagnostic Journey of Friedreich's Ataxia in the State of São Paulo, Brazil

Friedreich's Ataxia (FRDA) is the leading cause of ataxia worldwide, but data on epidemiology and diagnostic journey are scarce, particularly in Latin America. Herein we estimated the prevalence of FRDA in the most populous Brazilian state and characterized the diagnostic odyssey of the disease. We received anonymized data of patients with FRDA from advocacy groups and physicians. Prevalence was estimated dividing the number of patients by the population of the state as reported in the last census. Patients were invited to answer an online survey to describe clinical data and diagnostic journey of the disease. FRDA estimated prevalence was 0.367:100,000, with a slight predominance of women (58.2% vs 41.7%). One hundred and four patients answered the survey (mean age of 37.3 ± 13.8 years; 75.9% classical and 24.0% late onset). On average, 6.2 ± 4.1 physicians were visited before reaching the diagnosis. Mean diagnostic delay was 7.8 ± 6.7 years; no difference between classical and LOFA groups was found. Most of the patients reported unsteadiness and gait abnormalities as the first symptom. Neurologists and orthopedical surgeons were the main specialties first sought by patients. We found a prevalence of 0.36:100,000 for FRDA in the state of São Paulo, Brazil. The disease is characterized by remarkable diagnostic delay, with no relevant differences between classical and LOFA patients.

[Recent clinical advances in hereditary spinocerebellar degeneration]

Spinocerebellar degeneration (SCD) is a neurodegenerative disorder characterized by cerebellar ataxia and other multisystem manifestations, such as Parkinsonism and pyramidal tract symptoms. No effective treatment is available for SCD. Approximately one-third of the cases of SCD are inherited, and the remaining two-third are sporadic, including multiple system atrophy. This article provides an overview of hereditary SCD, its clinical features, recent treatment advances, biomarkers, role of genomic medicine, and future treatment prospects.

Prevalence of repeat expansions causing autosomal dominant spinocerebellar ataxias in Hokkaido, the northernmost island of Japan

In Japan, approximately 30% of spinocerebellar degeneration (SCD) is hereditary, and more than 90% of hereditary SCD is autosomal dominant SCD (AD-SCD). We have previously reported the types of AD-SCD in Hokkaido, twice. In this study, we investigated the status of AD-SCD mainly due to repeat expansions, covering the period since the last report. We performed genetic analysis for 312 patients with a clinical diagnosis of SCD, except for multiple system atrophy at medical institutions in Hokkaido between January 2007 and December 2020. The median age at the time of analysis was 58 (1-86) years. Pathogenic variants causing AD-SCD due to repeat expansion were found in 61.5% (192 cases). Spinocerebellar ataxia (SCA) 6 was the most common type in 25.3% (79 cases), followed by Machado-Joseph disease (MJD)/SCA3 in 13.8% (43), SCA1 in 6.4% (20), SCA2 in 5.1% (16), SCA31 in 4.8% (15), dentatorubral-pallidoluysian atrophy in 4.8% (15), SCA7 in 0.6% (2), and SCA8 in 0.6% (2). SCA17, 27B, 36, and 37 were not found. Compared to previous reports, this study found a higher prevalence of SCA6 and a lower prevalence of MJD/SCA3. An increasing number of cases identified by genetic testing, including cases with no apparent family history, accurately revealed the distribution of disease types in Hokkaido.

A retrospective study of autoimmune cerebellar ataxia over a 20-year period in a single institution

BACKGROUND

It is important to differentiate autoimmune cerebellar ataxia (ACA) from neurodegenerative CA, but this is sometimes difficult. We performed a retrospective study in a single institution in Japan over a 20-year period to reveal the clinical features of ACA.

METHODS

Patients with CA as the primary neurological symptom were enrolled from those admitted to the Department of Neurology, Hokkaido University Hospital between April 2002 and March 2022. ACA was diagnosed retrospectively according to the following criteria: (1) CA being the predominant symptom; (2) identification of cancer within 2 years of onset; (3) improvement in cerebellar symptoms following immunotherapy; and (4) ruling out alternative causes of CA. Patients fulfilling criteria (1), (2), and (4) were classified as paraneoplastic cerebellar degeneration (PCD), while those fulfilling (1), (3), and (4) were classified as non-PCD and enrolled as patients with ACA. Neurodegenerative diseases, e.g., multiple system atrophy (MSA), were confirmed retrospectively based on generally used diagnostic criteria and enrolled. Furthermore, the ACA diagnostic criteria proposed by Dalmau and Graus were applied retrospectively to the ACA patients to examine the validity of the diagnoses.

RESULTS

Among the 243 patients with CA, 13 were enrolled as ACA; five were PCD and eight were non-PCD. Eight of these cases met the proposed diagnostic criteria by Dalmau and Graus. MSA was the most prevalent disease among CA patients, with 93 cases. The incidence of cerebellar atrophy was significantly lower in ACA (3/13) than in MSA (92/92). Cerebrospinal fluid (CSF) pleocytosis was significantly more frequent in ACA than in MSA (4/13 vs. 2/55, respectively). However, there was no significant difference in the presence of oligoclonal bands, increased protein in CSF, and laterality differences in ataxia.

CONCLUSION

ACA was present in ~ 5% of Japanese CA patients. The absence of cerebellar atrophy, despite the presence of CA, strongly supports ACA over MSA. While CSF pleocytosis was observed more often in ACA, the positivity rate was only ~ 30%. Since ACA is treatable, further studies are needed to identify additional clinical features and accurate diagnostic biomarkers.

Spinocerebellar ataxias in Asia: Prevalence, phenotypes and management

This paper reviews and summarizes three main aspects of spinocerebellar ataxias (SCA) in the Asian population. First, epidemiological studies were comprehensively reviewed. Overall, the most common subtypes include SCA1, SCA2, SCA3, and SCA6, but there are large differences in the relative prevalence of these and other SCA subtypes between Asian countries. Some subtypes such as SCA12 and SCA31 are rather specific to certain Asian populations. Second, we summarized distinctive phenotypic manifestations of SCA patients of Asian origin, for example a frequent co-occurrence of parkinsonism in some SCA subtypes. Lastly, we have conducted an exploratory survey study to map SCA-specific expertise, resources, and management in various Asian countries. This showed large differences in accessibility, genetic testing facilities, and treatment options between lower and higher income Asian countries. Currently, many Asian SCA patients remain without a final genetic diagnosis. Lack of prevalence data on SCA, lack of patient registries, and insufficient access to genetic testing facilities hamper a wider understanding of these diseases in several (particularly lower income) Asian countries.

The First Case of Spinocerebellar Ataxia Type 8 in Monozygotic Twins

Spinocerebellar ataxia type 8 (SCA8) is a rare hereditary cerebellar ataxia showing mainly pure cerebellar ataxia. We herein report cases of SCA8 in Japanese monozygotic twins that presented with nystagmus, dysarthria, and limb and truncal ataxia. Their ATXN8OS CTA/CTG repeats were 25/97. They showed similar manifestations, clinical courses, and cerebellar atrophy on magnetic resonance imaging. Some of their pedigrees had nystagmus but not ataxia. These are the first monozygotic twins with SCA8 to be reported anywhere in the world. Although not all subjects with the ATXN8OS CTG expansion develop cerebellar ataxia, these cases suggest the pathogenesis of ATXN8OS repeat expansions in hereditary cerebellar ataxia.

Friedreich Ataxia: Diagnostic Yield and Minimal Frequency in South Brazil

Friedreich ataxia (FRDA) is an autosomal recessive disorder due to mutations in the FXN gene. FRDA is characterized by the classical triad of ataxia, absent reflexes, and Babinski sign, but atypical presentations might also occur. Our aims were to describe the proportion of FRDA diagnoses in suspected families living in Rio Grande do Sul, South Brazil, and to estimate a minimum frequency of symptomatic subjects. Subjects that were evaluated by molecular analysis for FRDA at the Hospital de Clínicas de Porto Alegre were identified in our files. Patients' clinical manifestation and phenotypes were described and compared. The number of FRDA subjects alive in the last 5 years was determined. One hundred fifty-six index cases (families) were submitted to evaluation of GAA repeats at FXN since 1997: 27 were confirmed as FRDA patients. Therefore, the diagnostic yield was 17.3%. Proportion of classical, late onset, and retained reflexes subphenotypes were similar to those described by other studies. A minimum prevalence was estimated as 0.20:100.000 inhabitants. In conclusion, we verified that this FRDA population displayed the usual clinical characteristics, but with a lower period prevalence than those obtained in populations from Europe.

Autosomal Dominant Spinocerebellar Ataxias: An Asian Perspective

Autosomal dominant cerebellar ataxias, frequently referred to as spinocerebellar ataxias (SCAs) have been under intense scientific research limelight since expansions of coded CAG trinucleotide repeats were demonstrated to cause several dominantly inherited SCAs. The number of new SCA loci has expanded dramatically in recent years. At least ten genes have been identified for SCAs 1, 2, 3, 6, 7, 8, 10, 12, 17, dentatorubral-pallidoluysian atrophy (DRPLA), and six loci responsible for SCAs 4, 5, 11,13, 14, and 16 have been mapped. Genetic testing is essential for diagnosis due to the overlapping and varied phenotypic features of the different SCAs. While there is no effective treatment available, genetic counseling is important for addressing the many ethical, social, legal, and psychological issues facing SCA patients. Researchers have recently provided valuable information on the pathogenesis of the disease and hopefully a cure will be available in the near future.

Spinocerebellar ataxia type 7

Spinocerebellar ataxia type 7 (SCA7) is associated with progressive blindness, dominant transmission, and marked anticipation. SCA7 represents one of the polyglutamine expansion diseases with increase of CAG repeats. The gene maps to chromosome 3p12-p21.1. Normal values of CAG repeats range from 4 to 18. The SCA7 gene encodes a protein of largely unknown function, called ataxin-7. SCA7 is reported in many countries and ethnic groups. Its phenotypic expression depends on the number of expanded repeats. The infantile phenotype is very severe, with more than 100 repeats. The classic type has 50 to 55 repeats and is characterized by a combination of visual and ataxic disturbances lasting for 20-40 years.When the number of CAG repeats is between 36 and 43, the evolution is much slower, with few or no retinal abnormalities. A CAG repeat number from 18 to 35 is asymptomatic but predisposes to the development of the disorder when expanding to the pathological range through transmission. The diagnosis is made by molecular genetics. The neuropathology of the disorder includes atrophy of the spinocerebellar pathways, pyramidal tracts, and motor nuclei in the brainstem and spinal cord, a cone-rod sytrophy of the retina, and ataxin-7 immunoreactive neuronal intranuclear inclusions. The neuropathological features vary as a function of the number of CAG repeats. Present research deals mainly with the study of ataxin-7 in transfected neural cells and transgenic mouse models.

Spectrum and prevalence of autosomal dominant spinocerebellar ataxia in Hokkaido, the northern island of Japan: a study of 113 Japanese families

Autosomal dominant cerebellar ataxia (ADCA) is a genetically heterogeneous group of neurodegenerative disorders. To shed further light on the clinical and genetic spectrum of ADCA in Japan, we conducted a study to determine the frequency of a new variety of different subtypes of SCAs among ADCA patients. This current study was carried out from April 1999 to December 2006 on the basis of patients with symptoms and signs of ADCA disorders. PCR and/or direct sequencing were evaluated in a total of 113 families. Among them, 35 families were found to have the mutation associated with SCA6, 30 with SCA3, 11 with SCA1, five with SCA2, five with DRPLA, and one with SCA14. We also detected the heterozygous -16C --> T single nucleotide substitution within the puratrophin-1 gene responsible for 16q22.1-linked ADCA in ten families. In this study, unusual varieties of SCA, including 27, 13, 5, 7, 8, 12, 17, and 16 were not found. Of the 113 patients, 14% had as yet unidentified ADCA mutations. The present study validates the prevalence of genetically distinct ADCA subtypes based on ethnic origin and geographical variation, and shows that 16q-linked ADCA has strong hereditary effects in patients with ADCAs in Japan.

Cambodian founder effect for spinocerebellar ataxia type 3 (Machado–Joseph disease)

Four families from the same region of Cambodia immigrated to the Pacific Northwest of the United States. All four families have been discovered to have spinocerebellar ataxia type 3 (SCA 3; Machado-Joseph disease) with a similar clinical phenotype. CAG repeat expansions in the ATXN3 gene range from 72 to 77. Mean age of onset has varied from 19 to 44 years and mean age at death of 4 individuals has been 60 years. The prevalence of the various subtypes of SCA varies worldwide from country to country. Neurologists should be alert to the possibility of SCA 3 in Cambodian patients with unexplained cerebellar ataxia.

Adult onset spinocerebellar ataxia in a Canadian movement disorders clinic

BACKGROUND

The spinocerebellar ataxias (SCAs) are a genetically and clinically heterogeneous group of neurodegenerative disorders. Relative frequencies vary within different ethnic groups and geographical locations.

OBJECTIVES

1) To determine the frequencies of hereditary and sporadic adult onset SCAs in the Movement Disorders population; 2) to assess if the fragile X mental retardation gene 1 (FMR1) premutation is found in this population.

METHODS

A retrospective chart review of individuals with a diagnosis of adult onset SCA was carried out. Testing for SCA types 1, 2, 3, 6, 7, and 8, Dentatorubral-pallidoluysian atrophy (DRPLA), Friedreich ataxia and the FMR1 expansion was performed.

RESULTS

A total of 69 patients in 60 families were identified. Twenty-one (35%) of the families displayed autosomal dominant and two (3.3%) showed autosomal recessive (AR) pattern of inheritance. A positive but undefined family history was noted in nine (15%). The disorder appeared sporadic in 26 patients (43.3%). In the AD families, the most common mutation was SCA3 (23.8%) followed by SCA2 (14.3%) and SCA6 (14.3%). The SCA1 and SCA8 were each identified in 4.8%. FA was found in a pseudodominant pedigree, and one autosomal recessive pedigree. One sporadic patient had a positive test (SCA3).Dentatorubral-pallidoluysian atrophy and FMR1 testing was negative.

CONCLUSION

A positive family history was present in 53.3% of our adult onset SCA patients. A specific genetic diagnosis could be given in 61.9% of dominant pedigrees with SCA3 being the most common mutation, followed by SCA2 and SCA6. The yield in sporadic cases was low. The fragile X premutation was not found to be responsible for SCA.

Insights into the mutational history and prevalence of SCA1 in the Indian population through anchored polymorphisms

There is a wide variation in prevalence of spinocerebellar ataxia type 1 (SCA1) in different populations. In the present study, we observed SCA1 in approximately 22% (37/167 families) of the autosomal dominant cerebellar ataxias (ADCAs) in the Indian population. We investigated the role of various genetic factors like repeat length, interruption pattern and chromosomal background in predisposing the repeats to instability in these families. We analyzed 12 markers (9 SNPs and 3 microsatellite markers) and found 3 of them, spanning a region of approximately 65 kbp to be linked with the disease locus in the Indian population. The haplotype C-4-C defined by rs1476464 (SNP9)-D6S288-rs2075974 (SNP1), which was extremely rare in nonaffected chromosomes (approximately 3%), was observed to be significantly (P<0.0000) associated with the expanded chromosomes in approximately 44% of SCA1 families. This haplotype was found in all nonhuman primates. SNP1 (C/T), which showed a skewed allelic distribution between large (LN > 30 repeats) and small normal (SN <or= 30 repeats) alleles (P<0.0000) had similar allelic distribution (P=0.3477) in LN and expanded alleles. Our study suggested that LN and expanded chromosomes linked with the ancestral C allele of SNP1 might have originated simultaneously during evolution by the lengthening of repeats. The LN alleles might have accumulated repeat stabilizing non-CAG interruptions during this process. Similar proportions of T allele in SN with single interruptions, LN and expanded chromosomes lend credence to the origin of expanded alleles from singly-interrupted chromosomes. Our analyses using markers linked (anchoring) to SCA1 suggest that prevalence of SCA1 is correlated to both repeat length and number of interruptions in the Indian population. The spectrum of these alleles also points toward the antiquity of SCA1 mutation in the Indian population.

Degeneration of the inferior olive in spinocerebellar ataxia 6 may depend on disease duration: report of two autopsy cases and statistical analysis of autopsy cases reported to date

This report concerns a clinicopathological study of two autopsied patients with spinocerebellar ataxia 6 (SCA6), and a statistical analysis between neuronal loss of the inferior olive and disease duration of 15 SCA6 autopsy cases reported to date, including the two cases reported in this study. Cases 1 and 2 came from independent Japanese families. Case 1 developed gait disturbance at age 35 years and died at age 78 years; she had a CAG-repeat expansion of the SCA6 gene (25/13). Case 2 presented with gait disturbance at age 68 years and died at age 78 years; he had an expanded CAG-repeat of the SCA6 gene (22/13). Neuropathological examination of both cases disclosed not only neuronal loss of the Purkinje cells and inferior olive, but also some unnoticed features, including cactus-like expansion of the dendrite of Purkinje cells and relative preservation of Golgi cells in the granular layer of the cerebellum. Exploratory statistical analysis between 11 SCA6 autopsy cases with neuronal loss in the inferior olive (average disease duration: 27 years) and four SCA6 autopsy cases without neuronal loss in the olive (average disease duration: 14.5 years) was investigated by Kaplan-Meier estimates of survival and log-rank test, retrospectively. Kaplan-Meier estimates of survival revealed an obvious difference between the two groups. Survival of 10 years after the disease onset was 90.9% in the former 11 SCA6 autopsy cases, but was 50% in the latter four SCA6 autopsy cases. Furthermore, a log-rank test on the two groups disclosed a significant difference (P=0.0450). We postulate that the neuronal loss of the inferior olive in SCA6 may depend on disease duration.

Genetic admixture of European FRDA genes is the cause of Friedreich ataxia in the Mexican population

Friedreich ataxia accounts for approximately 75% of European recessive ataxia patients. Approximately 98% of pathogenic chromosomes have large expansions of a GAA triplet repeat in the FRDA gene (E alleles), and strong linkage disequilibrium among polymorphisms spanning the FRDA locus indicates a common origin for all European E alleles. In contrast, we found that only 14 of 151 (9.3%) Mexican Mestizo patients with recessive ataxia were homozygous for E alleles. Analysis of polymorphisms spanning the FRDA locus revealed that all Mestizo E alleles had the common European haplotype, indicating that they share a single origin. Genetic admixture levels were determined, which revealed that the relative contributions to the Mestizo FRDA gene pool by Native American and European genes were 76-87% and 13-24%, respectively, commensurate with the observed low prevalence of Friedreich ataxia in Mestizos. This indicates that Friedreich ataxia in Mexican Mestizos is due to genetic admixture of European mutant FRDA genes in the Native American gene pool that existed prior to contact with Europeans.

The occurrence of dominant spinocerebellar ataxias among 251 Finnish ataxia patients and the role of predisposing large normal alleles in a genetically isolated population

OBJECTIVES

Frequency and distribution of dominant ataxias caused by dynamic mutations may vary in different populations, which has been explained on the basis of relative frequency of predisposing normal alleles. The aim of the study was to evaluate the occurrence of spinocerebellar ataxias (SCAs) and dentatorubral-pallidoluysian atrophy (DRPLA) in Finland, and to investigate the role of predisposing normal alleles in a genetically homogenous population.

MATERIAL AND METHODS

Mutation analyses for SCA1, 2, 3, 6, 7, 8, 10, 12, 17, and DRPLA and frataxin genes were performed for 251 unrelated Finnish patients who presented with progressive ataxia disorder.

RESULTS

Expansions of SCA1, SCA2, SCA6, SCA7, SCA8, and SCA17 genes were detected in 2, 1, 1, 7, 22, and 1 patients, respectively. Altogether, 39 and 7% of dominant and sporadic SCA patients, respectively, harboured expansions at some of the investigated loci. Normal variation, collected from 477 to 502 chromosomes at each disease loci, revealed that Finns were different from the Japanese but largely similar to other Caucasians.

CONCLUSIONS

Lack of SCA3 and excess of SCA8 are characteristic to the Finnish population. Homozygosity for the SCA8 expansion increases penetrance. Frequencies of large normal alleles at the SCA loci predict poorly prevalence of the respective diseases in Finland. Prioritization in DNA testing, based on ethnic origin and geographical location, is recommendable in Finland, and analogous approach may be applied to other countries as well.

Prevalence of inherited ataxias in the province of Padua, Italy

Few population studies are available on epidemiological indexes of hereditary ataxias. An investigation on the prevalence rate of these movement disorders is in progress for the Veneto region, the main area of northeast Italy with a population of 4,490,586 inhabitants. The first results of this epidemiological survey concern the province of Padua, which numbers 845,203 residents (January 1, 2002). The prevalence rate of inherited ataxias has been estimated at 93.3 cases per million inhabitants. The most common types appeared to be the autosomal dominant forms, namely spinocerebellar ataxia type 1 and 2, with a prevalence of 24 per 1,000,000. In the same population, with a prevalence rate of 6 per 1,000,000, Friedreich's ataxia was defined as the prominent recessive autosomal form. There were very rare cases of ataxia telangiectasia, ataxia with vitamin E deficiency and cerebellar ataxia with congenital muscular dystrophy, a recently identified autosomal recessive disease.

A clinical and genetic study in a large cohort of patients with spinocerebellar ataxia type 6

In order to clarify the clinical and genetic features of SCA6, we retrospectively analyzed 140 patients. We observed an inverse correlation between the age of onset and the length of the expanded allele, and also between the age of onset and the sum of CAG repeats in the normal and the expanded alleles. The ages of onset of four homozygous patients correlated better with the sum of CAG repeats in both alleles rather than with the expanded allele calculated from heterozygous SCA6 subjects. Clinically, unsteadiness of gait was the main initial symptom, followed by vertigo and oscillopsia, and cerebellar signs were detected in nearly 100% of the patients. In contrast, extracerebellar signs were relatively mild and infrequent. The results of neuro-otological examination performed in 22 patients suggested the purely cerebellar abnormalities of ocular movements in nature. There was a close relationship between downbeat positioning nystagmus (DPN) and positioning vertigo, which became more common in the later stage. We conclude that total number of CAG repeat-units in both alleles is a good parameter for assessment of age of onset in SCA6 including homozygous patients. In addition, clinical and neuro-otological examinations suggested that SCA6 is a disease with predominantly cerebellar dysfunction.

Spinocerebellar ataxia type 8 in Scotland: genetic and clinical features in seven unrelated cases and a review of published reports

OBJECTIVES

To establish whether the DNA expansion linked to spinocerebellar ataxia type 8 (SCA 8) is associated with ataxia in Scotland; to clarify the range of associated clinical phenotypes; and to compare the findings with previous reports.

METHODS

DNA was screened from 1190 anonymised controls, 137 subjects who had tested negative for Huntington's disease, 176 with schizophrenia, and 173 with undiagnosed ataxia. Five unrelated ataxic patients with the SCA 8 expansion and a sixth identified subsequently had clinical and psychometric assessment; the clinical features were available in a seventh. A systematic search for other reports of SCA 8 was undertaken.

RESULTS

Over 98% of SCA 8 CTA/CTG repeat lengths fell between 14 and 40. Repeat lengths over 91 were observed in three healthy controls (0.12%), two patients with suspected Huntington's disease (0.73%), and six ataxic subjects (1.74%; p<0.0005 v healthy controls). Repeat lengths over 100 occurred in five ataxic subjects but in only one control. All seven symptomatic subjects with the SCA 8 expansion had a cerebellar syndrome; four had upper motor neurone signs; and 5/6 assessed had cognitive complaints. There was personality change in two and mood disturbance in three. In published reports, SCA 8 repeat lengths over 91 occurred in approximately 0.5% of the healthy population but were over-represented among ataxic patients (3.4%; p<0.0001). The predominant clinical phenotype was cerebellar, with pyramidal signs in 50%, and neuropsychiatric features in some cases.

CONCLUSIONS

SCA 8 expansion is a risk factor for a cerebellar syndrome, often associated with upper motor neurone and neuropsychiatric features. The expansion occurs unexpectedly often in the general population.

Variation of CAG repeats and two intragenic polymorphisms at SCA3 locus among Machado-Joseph disease/SCA3 patients and diverse normal populations from eastern India

OBJECTIVES

MJD1/SCA3 is the most common type of spinocerebellar ataxia (SCA) worldwide. To explain the low prevalence of the disease among SCA patients from eastern India, we analysed CAG repeats and two bi-allelic intragenic markers at SCA3 locus among 412 normal individuals and 10 patients.

MATERIALS AND METHODS

For CAG repeat analysis, PCR amplified fragments were run on polyacrylamide gel, transferred to a membrane, probed with (CAG)10 and detected on an autoradiograph. Bi-allelic markers were analysed using allele specific PCR amplification.

RESULTS

Large normal alleles (>33 CAG repeats) were 0.015 in pooled populations. All the patients had the common haplotype C-A as observed worldwide. Frequency of C-A haplotype among large normal alleles was 0.75.

CONCLUSIONS

Observed low prevalence of SCA3 could be because of the low prevalence of large normal alleles that might act as the reservoir for the expanded alleles. SCA3 mutation in Indian populations had the same origin as found worldwide.

The hereditary spinocerebellar ataxias in Japan

In Japan, multiple system atrophy (MSA) accounts for 40% of all spinocerebellar ataxias (SCAs) and hereditary disorders account for 30%. Among the latter, autosomal dominant disorders are common and recessive ataxias are rare. Although the frequency of SCA genotypes differs between geographic regions throughout Japan, SCA6, SCA3/MJD, and DRPLA are the three major disorders, while SCA7, SCA8, SCA10, SCA12, and SCA17 are infrequent or almost undetected. SCA1 predominantly occurs in the northern part of Japan. Overall, 20-40% of dominant SCAs are due to unknown mutations. From this cluster, pure cerebellar ataxias linked with the SCA4, SCA14, and SCA16 locus have been isolated. Among the recessive SCAs, patients with AVED and EAOH have been detected. However, FRDA associated with GAA repeat expansion in the frataxin gene has not been reported so far.

Prevalence and ethnic differences of autosomal-dominant cerebellar ataxia in Singapore

We report the prevalence and ethnic differences of autosomal-dominant cerebellar ataxia (ADCA) in Singapore. Amongst 204 patients with ataxia who underwent genetic testing for dentatorubral-pallidoluysian atrophy (DRPLA) and for spinocerebellar ataxias (SCA) 1, 2, 3, 6, 7, 8, 10 and 12, 58 (28.4%) patients from 36 families tested positive. SCA 3 was identified in 31 (53.4%) patients from 15 families, SCA 2 in 17 (29.3%) patients from 12 families and SCA 1 in four (6.9%) patients from four families. Other SCA subtypes were rare. SCA 2 was the only subtype identified amongst ethnic Malay and ethnic Indian families. The estimated prevalence of ADCA in Singaporean families was at least 1 : 27,000. Based on the history and ancestry of Singaporeans, our study supported a founder effect for specific SCA subtypes and the association of ethnicity-specific SCA subtypes. Our findings suggest that SCA 2 is relatively common amongst the Malay race and that priority testing for SCA 3 and SCA 2 for ethnic Chinese, and SCA 2 for ethnic Malay, may be cost effective and relevant for the region.

Difference in disease-free survival curve and regional distribution according to subtype of spinocerebellar ataxia: a study of 1,286 Japanese patients

Expansions of trinucleotide repeats have been discovered in spinocerebellar ataxia (SCA) types 1, 2, 6, 7, 12, and 17, Machado-Joseph disease (MJD/SCA3), and dentatorubropallidoluysian atrophy (DRPLA). However, the frequency of familial SCA in Japan remains unclear. The number of trinucleotide repeats was determined for 1,286 patients. Three hundred and thirty families (523 cases) were autosomal dominant group (A), and 165 families were positive for family history but not autosomal dominant group (B), while the remaining 598 cases were the sporadic group (C). The frequency of SCA subtypes in autosomal dominant group was: 1) 5.5% for SCA1; 2) 2.4% for SCA2; 3) 27.6% for MJD/SCA3; 4) 25.5% for SCA6; 5) 0.3% for SCA17; and 6) 7.3% for DRPLA. Abnormal expansion of SCA12 was not detected. Another 31.5% of the patients in the autosomal dominant group had unknown genetic abnormalities. Within group B, SCA6 was the most prominent and within the sporadic group MJD/SCA3 and SCA6 were the most common subtypes observed. The disease-free survival curve of SCA6 was different from that of other SCAs and the mean age at onset for SCA6 was found to be later than that of the other types. Regional differences were observed in the relative rate of SCA subtypes. MJD/SCA3 appears more common in the Kanto and Kyushu districts of Japan, whereas SCA6 is most common in the Chugoku district. In order to establish an effective social welfare system for SCA patients, clinical course and regional differences in the prevalence of SCA subtypes must be taken into consideration.

Autosomal dominant palatal myoclonus and spinal cord atrophy

We report a new family with palatal myoclonus, pyramidal tract signs, cerebellar signs, marked atrophy of the medulla oblongata and spinal cord, and autosomal dominant inheritance. These findings were almost identical with those in patients previously reported to have histopathologically confirmed adult-onset Alexander disease. Recently, heterozygous point mutations in the coding region of glial fibrillary acidic protein (GFAP) in patients with an infantile form of Alexander disease have been reported. We found a new heterozygous amino acid substitution, Val87Gly in exon 1 of GFAP, in the affected individuals in this family but not in 100 spinocerebellar ataxia (SCA) patients and 100 controls. Therefore, this family might have new clinical entities related to adult-onset Alexander disease and GFAP mutation.

Autosomal dominant cerebellar ataxias in ethnic Bengalees in West Bengal - an Eastern Indian state

BACKGROUND

Phenotypic and genotypic patterns of a hereditary disease in a large multiethnic country like India need to be studied in relation to geographical location and ethnicity of the population. The few reported studies from India on dominant ataxias (ADCA) have mostly been conducted on multiethnic populations and hence may not reflect the patterns observed in specific ethnic groups or geographical locations. The present study attempted to look into the patterns of ADCA amongst ethnic Bengalee patients hailing from the eastern Indian state of West Bengal.

MATERIAL AND METHODS

Between mid-1996 and mid-2000, in a clinic based study, 37 cases (from 14 families) with ADCA were studied. This included 33 affected and four asymptomatic members with abnormal physical signs. Genotypic analyses were performed on more than one affected member from each family. Clinical, neuroradiological and electrophysiological aspects were studied.

OBSERVATIONS

Genotype analysis revealed: two families with SCA-1,4 families with SCA2,5 families with SCA3 and three families with undetermined genotype. Of the latter, phenotypically 2 were of ADCA 1 and one of ADCA 2 type. No clear preponderance of one particular genotype over another was observed. We noted significant intra- and interfamily variations in phenotype within the same genotype form as well as overlapping of clinical signs between different genotypes. Slow saccadic eye movements and peripheral neuropathy were not seen consistently in our ethnic Bengalee subjects with SCA2 genotypes. Similarly, extrapyramidal features, ophthalmoplegias and distal amyotrophy were seen in some but not in all families with SCA3 mutation. A peculiar form of abduction lag during slow pursuit movement of eyes was observed in an asymptomatic girl in an SCA3 family.

CONCLUSIONS

Although SCA2 has been claimed to be the commonest form of ADCA in India, this does not appear to be so in our ethnic Bengalee subjects. Phenotypic expression of the genotype also appears to be variable amongst families and individuals. Hence, phenotypic expression appears to be an inconsistent marker of the SCA genotype in our patients.

Machado-Joseph disease with retinal degeneration and dementia

OBJECTIVES

To clarify the phenotypic varieties in Machado-Joseph disease (MJD).

MATERIALS AND METHODS

We studied a 64-year-old man with ataxia, retinal degeneration and dementia neurologically, ophthalmologically and genetically.

RESULTS

The patient noted dysesthesia of his hands at age 57 and later had memory disturbance. He had gait disturbance and needed a wheelchair at age 64. His total IQ was 61 on the WAIS-R. He had loss of central vision, ophthalmoplegia, hearing impairment, dysarthria, truncal and limb ataxia, sensory disturbance, and mild weakness of the extremities. Electrophysiologically he was suspected to have polyneuropathy. Brain MRI showed marked atrophy of the cerebellum and pons with mild cerebral atrophy. Ophthalmologic evaluation revealed multiple chorioretinal atrophy. Expanded CAG repeat numbers in MJD1 were 64.

CONCLUSION

These findings indicate that the clinical features of MJD might cover a wider spectrum than previously expected, though it is possible that these complications, namely retinal degeneration and dementia, were incidental findings in this patient.

Effects of tetrahydrobiopterin on ataxia in Machado-Joseph disease may be based upon the theory of 'cerebellar long-term depression'

We previously verified the effectiveness of tetrahydrobiopterin (BH4) on the ataxia in Machado-Joseph disease (MJD; SCA3 [spinocerebellar ataxia type 3]) as one of the most common types of dominantly inherited spinocerebellar ataxias. We hypothesized as to the pharmacological mechanism of BH4 that on the basis of 'cerebellar long-term depression' theory, BH4 may exert its actions at the levels of soluble guanylate cyclase in the Purkinje cells and of nitric oxide synthase in the granule cells. If cerebellar long-term depression is the case as the theoretical basis of BH4, it will open a new page of therapeutic strategy for spinocerebellar ataxias.

Meiotic instability of the CAG repeats in the SCA6/CACNA1A gene in two Japanese SCA6 families

Intergenerational stability of the CAG repeat number has been considered to be a specific molecular feature of SCA6 compared with other CAG repeat diseases. Nevertheless, we showed meiotic instability of the CAG repeats in the SCA6/CACNL1A gene in two Japanese SCA6 families, including de novo expansion. In one family, the CAG20 allele expanded to the CAG26 one during paternal transmission, and in the other family, the CAG19 allele expanded to the CAG20 one during maternal transmission. Although it is controversial as to whether the CAG20 allele is pathological or not, this is the first case of haplotype analysis-proven de novo expansion in SCA6, confirming the derivation of an expanded allele from one normal allele. We should carefully follow up the individuals carrying the CAG20 allele in our family who show normal neurological and radiological findings at present.

High prevalence of spinocerebellar ataxia type 1 (SCA1) in an isolated region of Japan

Autosomal dominant cerebeller ataxias (ADCAs) are a heterogeneous group of neurodegenerative disorders that differ in both the clinical manifestations and modes of inheritance. At present, eight different genes causing ADCAs have been found: spinocerebeller ataxia type 1 (SCA1), SCA2, SCA3/Machado-Joseph disease (MJD), SCA6, SCA7, SCA8, SCA12 and dentatorubropallidoluysian atrophy (DRPLA). The relative prevalence of each mutation varies according to race and native place. We studied 117 unrelated ADCA families that originated from the Tohoku District in the northernmost part of Honshu Island in Japan (mainly Miyagi Prefecture in the central part of Tohoku District). The SCA1 mutation was the most frequent among the known disorders (24.8% of all such families). The relative prevalence of SCA1 in the Tohoku District is very high compared with the values already reported from other regions in the world. Because the population of this area had seldom moved, the alleles with SCA1 mutations (including alleles with an intermediate CAG repeat number) are assumed to have been present in this area for a long time.

A novel locus for dominant cerebellar ataxia (SCA14) maps to a 10.2-cM interval flanked by D19S206 and D19S605 on chromosome 19q13.4-qter

Dominantly inherited, late-onset pure cerebellar ataxia is a group of genetically heterogeneous neurodegenerative disorders. Approximately half of these disorders in the Japanese population are caused by moderate expansion of a CAG repeat in the coding region of the CACNA1A gene on chromosome 19p13 (SCA6). However, neither the loci nor the specific mutations for the remaining disorders have been determined. We performed systematic linkage analysis in a three-generation Japanese family with a locus or mutation that differed from those of known spinocerebellar ataxias. The family members with a late onset (> or =39 years old) exhibited pure cerebellar ataxia, whereas those with an early onset (< or =27 years old) first showed intermittent axial myoclonus followed by ataxia. Other neurological signs were sparse, and neuroimaging studies revealed that atrophy was confined to the cerebellum. Multipoint analysis and haplotype reconstruction ultimately traced this novel spinocerebellar ataxia locus (SCA14) to a 10.2-cM interval flanked by D19S206 and D19S605 on chromosome 19q13.4-qter (Zmax = 4.08, corrected for age-dependent penetrance).