Hereditary Cerebellar Ataxias: A Korean Perspective

Article information

J Mov Disord. 2015;8(2):67-75
Publication date (electronic) : 2015 May 31
doi : https://doi.org/10.14802/jmd.15006
1Department of Neurology, Soonchunhyang University Hospital, Soonchunhyang University School of Medicine, Seoul, Korea
2Department of Neurology, Sungkyunkwan University School of Medicine, Seoul, Korea
3Neuroscience Center, Samsung Medical Center, Seoul, Korea
Corresponding author: Jin Whan Cho, MD, PhD, Department of Neurology, Neuroscience Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-ro, Gangnam-gu, Seoul 135-710, Korea Tel: +82-2-3410-1279 Fax: +82-2-3410-0052 E-mail: jinwhan.cho@samsung.com
Received 2015 February 25; Revised 2015 April 14; Accepted 2015 April 16.

Abstract

Hereditary ataxia is a heterogeneous disorder characterized by progressive ataxia combined with/without peripheral neuropathy, extrapyramidal symptoms, pyramidal symptoms, seizure, and multiple systematic involvements. More than 35 autosomal dominant cerebellar ataxias have been designated as spinocerebellar ataxia, and there are 55 recessive ataxias that have not been named systematically. Conducting genetic sequencing to confirm a diagnosis is difficult due to the large amount of subtypes with phenotypic overlap. The prevalence of hereditary ataxia can vary among countries, and estimations of prevalence and subtype frequencies are necessary for planning a diagnostic strategy in a specific population. This review covers the various hereditary ataxias reported in the Korean population with a focus on the prevalence and subtype frequencies as the clinical characteristics of the various subtypes.

INTRODUCTION

The word ataxia means the “absence of order,” and the term describes a clinical syndrome of incoordination caused by the dysfunction of cerebellum and its connected pathway. Currently, “ataxia” indicates specific disorders of the central nervous system in which the prominent phenotype is progressive ataxia. Hereditary cerebellar ataxias are a clinically, pathologically, and etiologically heterogeneous group of disorders [1,2]. In the past, several attempts have been made to classify hereditary cerebellar ataxias based on neuropathological features or clinical manifestations [3-5]. As molecular genetic methods have developed, genetic classification is more commonly used to study these ataxias. Hereditary ataxias are categorized by inheritance patterns in the following categories: autosomal-dominant, autosomal-recessive, X-linked, or mitochondrial mode of inheritance [6,7].

The prevalence of hereditary ataxia can vary among countries because of the founder effect [8-12]. Although the estimations of prevalence and subtype frequencies are necessary for planning the diagnostic strategy in a specific population, large epidemiological research about hereditary cerebellar ataxias is relatively rare in Korea compared to western countries. Various factors, including the fact that Korea is mostly a racially homogeneous nation, the shortage of family history, the low rate of typical phenotypes, and limited commercially available genetic tests, make it difficult to obtain an accurate diagnosis of these ataxias.

This review introduces the frequencies of hereditary ataxic disorders in Korea and the phenotypic features that have been reported by clinical, epidemiological and molecular genetic studies.

AUTOSOMAL DOMINANT CEREBELLAR ATAXIAS (ADCA)

Autosomal dominant cerebellar ataxias (ADCA) frequently represent spinocerebellar ataxias (SCAs). They are numbered according to the order of detection in the genetic locus. Recently, numerous novel SCA loci have been detected at a rapid rate and have extended to SCA 40 (Table 1) [13-15]. SCAs can be subdivided into four groups according to genetic mechanism, as follows [16]: polyglutamine disease due to the expansion of coronary angiography (CAG) triplet repeats [SCAs 1, 2, 3, 6, 7, 17 and dentatorubral pallidoluysian atrophy (DRPLA)], intronic disease (SCA8, 10, 12, 31, and 36), conventional mutation SCAs (SCA5, 11, 13, 14, 19/22, 23, 26, 27, 28, 29, and 35) and SCA with large duplications or deletions (SCA15 and 20).

SCA: distinguishing features and molecular genetics

The first group (polyglutamine disease) is more prevalent than the other forms of SCAs, and the mechanisms of the disease are well known [13]. Polyglutamine disease has several characteristic genetic features. The translated protein of the expanded triplet gene contains abnormally elongated glutamine repeats. The size of the expanded repeat is inversely correlated with the onset age, progression rate and clinical severity, which is referred to as anticipation [17,18]. This phenomenon is most striking in SCA7 and DRPLA due to lack of stabilizing intrusions (CAA/CAT) [17], and the phenomenon is less prominent in SCA6 because of the relatively small expansion and intergenerational stability [13]. In the CAG repeat disorders, genetic imprinting is also frequently observed, so paternal transmission is more likely to be associated with the occurrence of repeat expansions than maternal transmission of the expanded allele [18].

The most common subtype of intronic disease is SCA8, and its unique mechanisms have been recently reported [19,20]. SCA8 is thought to be caused by the bidirectional expansion of CTG/CAG leading to ribonucleic acid (RNA)-mediated toxicity and pathogenic polyglutamine tract formation. In contrast to polyglutamine disease, SCA8 shows expansions of the CTG repeat more frequently while maternal inheritance.

The clinical features of SCA overlap each other, and it is difficult to distinguish the subtypes of SCA with clinical manifestations. However, there are several distinguishable symptoms in each type [21]. SCA2 differs clinically from other types of SCAs because of the slow saccade and hyporeflexia [22]. SCA2 may present parkinsonism or amyotrophic lateral sclerosis [23,24], and cognitive impairment has also been reported for this subtype. The common features of SCA3, which is the most common subtype and called Machado-Joseph disease, are parkinsonism, dystonia, faciolingual myokymia and bulging eyes [16,25]. SCA6 is a pure cerebellar syndrome. The distinguishing feature of SCA6 is pronounced cerebellar oculomotor disturbance, including positioning and perverted headshaking downbeat nystagmus [26,27]. Patients with SCA7 experience a decrease in visual acuity and slow saccade, which are the predominant signs of the disease [28]. The most distinctive feature of SCA7 is the visual loss caused by pigmentary retinopathy. The phenotype of SCA17 is highly variable and complex. Various combinations of ataxia, chorea, cognitive impairment and parkinsonism make up the clinical manifestation of SCA17 [29].

DRPLA might be a dominant SCA. DRPLA is caused by expansion of abnormal CAG repeats in the DRPLA gene on 12p13.31 [30]. The pathological features of DRPLA are characterized by diffuse, marked brain atrophy, including the brainstem, dentate nucleus and pallidoluysian pathways. Although most patients with DRPLA have ataxia, they often have marked phenotypical variation according to the age of onset [31]. Childhood and adolescent-onset patients frequently have seizures and myoclonus, whereas adult onset patients typically have psychiatric problems, dementia and chorea [32,33]. We reported that cerebral white matter involvement could be the characteristic finding when imaging DRPLA, and these features might be helpful for the differential diagnosis between DRPLA and SCAs in the early stages of cerebellar ataxias [34].

Prevalence of ADCA

Although numerous epidemiological reports have attempted to determine the prevalence of ataxias in defined regions, an accurate estimation has yet to be well defined. The prevalence of the ADCAs is estimated to occur in approximately 1–5 people out of 100,000 people worldwide [35]. Dutch and Norwegian surveys [36] found the prevalence of ADCA to be 3.0 and 4.2 per 100,000, respectively. Of the ADCA, SCA3 is the most common subtype worldwide, followed by SCA1, SCA2, SCA6, and SCA7 [35]. However, the prevalence of subtypes of ADCA may vary by regional group due to the founder effects. SCA3, also called Machado-Joseph disease, was first introduced in Portuguese group from the Azores [37] and is commonly detected in Brazil [38], Portugal [39], Germany [40], China [41], and Japan [42]. SCA2 is the commonest subtype in Spain [43], southern Italy [44], India [45], and Cuba [46]. DRPLA is most prevalent in Japan and rare in North America [47].

SCAs in Korea

The only nationwide survey in Korea was performed from 2011 to 2012 using data from the Health Insurance Review and Assessment Service as well as data from the National Health Insurance Corporation [48]. According to this report, the prevalence rate of hereditary cerebellar ataxia patients in Korea is 4.99 patients/100,000 people. However, this study was performed based on diagnosis codes registered in the national statistical data rather than accurate clinical diagnoses made by experts. There is a possibility that ataxic diseases may have been underestimated or overestimated. Therefore, the exact prevalence of ataxic disorders and the frequency of the SCA subtype are still unclear.

Several single center-based studies exploring the frequency of SCAs have been published [49-52], and most of them revealed that SCA2 is the most common subtype in Korea, except for one study. Jin et al.[51] reported the prevalence of the SCA subtypes in the Korean population first. They found that SCA2 is most prevalent subtype followed by SCA6, and 3. 8 of 47 (17%) ataxic patients who were diagnosed with SCA did not have a definite family history. In 2003, Lee et al. [50] analyzed the frequencies of SCA subtypes in 253 patients who showed progressive ataxia, and the CAG triplet expansion was detected in 52 patients (20.6%). The most frequent subtype was SCA2, followed by SCA3, 6, 1, and 7. Interestingly, 4 out of 52 patients were misdiagnosed with multiple system atrophy (MSA) due to the negative family history and the presence of parkinsonism and dysautonomia. In contrast with previous results, Kim et al. [49] found that SCA3 was the most frequent subtype in their study. In that report, the authors performed a molecular analysis of SCA1, 2, 3, 6, and 7 in 76 individuals who showed signs of progressive ataxia. Thirty of the 76 individuals showed CAG expansions, and the most frequent subtype was SCA3 (15.8%) followed by SCA2 (14.5%). Among the 30 patients who were confirmed as SCA based on genetic confirmation, 4 (13.3%) were sporadic cases and 2 (6.7%) did not show an autosomal dominant inheritance pattern. Recently, in a multi-center analysis investigating the regional distribution of SCAs, 351 patients with SCA were identified [53]. The most frequent subtype was SCA2 followed by SCA3 and 6, and these three subtypes represented more than 70% of all cases in Korea. The subtype frequencies of SCAs varied considerably among the regions. In Seoul, Incheon and Gyeonggi, the subtype frequencies were similar to the subtypes in the entire Korean population. SCA3 was more frequent in the central areas, SCA2 was more frequently detected in the southern areas, and 93.6% (15 of 16) cases in Jeju were SCA6. These regional differences might reflect the founder effect or a mixing pattern with surrounding populations.

DRPLAs in Korea

Although several sporadic cases of DRPLAs have been reported in western countries, DRPLA appears to be very rare except in Japan. However, DRPLA is not uncommon in Koreans. According to previous reports, DRPLA is found at a rate of 3.4–4% of the hereditary ataxias in the Korean population [51,53].

AUTOSOMAL RECESSIVE CEREBELLAR ATAXIAS (ARCA)

There are over 55 disorders with an autosomal recessive inheritance pattern, and the “big six” recessive ataxias include the following diseases: ataxiatelangiectasia (AT), Friedreich ataxia (FRDA), ataxia-ocular motor apraxia types 1 and 2 (AOA), autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), and POLG-related disorders.

Prevalence and clinical features of ARCA

Hereditary ataxias with autosomal recessive inheritance account for 3:100,000 cases worldwide. In Korea, patients with recessive ataxia are rare (Table 2). Although FRDA is the most common genetic ataxia in Caucasians (one-third of recessive ataxias are FRDA), it is extremely rare in east Asia. In Korea, a few cases of FRDA were reported, but there was no genetic confirmation [54,55]. AOA is the most common recessive ataxia in Japan, the second most common recessive ataxia in Portugal (representing approximately 4% of recessive ataxias), but AOA is also not reported in Korea. Therefore, this article will concentrate on recessive ataxias reported in Korea.

Reports of cerebellar ataxia with an autosomal recessive inheritance pattern in Korea

Ataxia telangiectasia

AT is caused by mutations in the ATM gene, and it is the second most common recessive ataxia worldwide. AT is characterized by progressive ataxia beginning in early childhood and telangiectasia. Clinical manifestations include cerebellar ataxia, oculomotor apraxia, choreoathetosis and dystonia. Physical examination reveals characteristic telangiectasias of the conjunctivae, nose, palate and cubital fossae. Patients with AT experience frequent respiratory infections due to immunodeficiency and they run a risk of malignancy because of radiosensitivity.

The prevalence of AT is estimated to be between 1 in 40,000 people and 1 in 300,000 people depending on ethnic specificity. Although AT is the most common cause of ataxia in childhood in most populations, it is rarely found in Korea. Four cases of AT have been reported in Korea, and only 2 cases were genetically confirmed with gene sequencing [56-59]. We reported a delayed diagnosis of AT with 2 novel splicing mutations in the ATM gene [56] because of subtle telangiectasias of conjunctivae. This case emphasized the importance of clinical suspicion of AT even though it is a rare and atypical clinical manifestation in Korea.

Cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive form of xanthomatosis caused by deficiency of the enzyme sterol 27-hydroxylase (CYP27), which results in the accumulation of cholesterol and cholestanol. CTX is caused by mutations in the CYP27A1 gene, which is located on chromosome 2q33-qter and manifests childhoodonset cataracts followed by adult-onset tendon xanthomas and progressive neurologic symptoms, including cerebellar ataxia, dystonia, cognitive impairments, and seizures.

There have been two cases of CTX diagnosed by gas chromatography [60] and gene confirmation [61]. In both cases, the typical phenotype developed in early childhood or adulthood, but the diagnosis was delayed for approximately 10 years. Metabolic issues can be improved by treatment with chenodeoxycholic acid. Furthermore, treatment can prevent neurological symptoms, so early diagnosis and treatment is important and essential for CTX.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay

ARSACS was introduced in Quebec, Canada, and is restricted to this area. The phenotype of ARSACS was very homogeneous and showed a typical triad of leg spasticity, peripheral neuropathy and infantonset cerebellar ataxia. After detecting the accountable gene, SACS, ARSACS has also been reported outside of Quebec in countries including Japan, Europe, and North Africa. Now we know that ARSACS is not an endemic disease in Quebec. Basically, the clinical manifestations of ARSCAS were reported to be very homogeneous in Quebec, and non-Quebec patients usually present with atypical phenotypes.

In Korea, only one case of ARSACS has occurred. The patient showed the classic triad of early childhood-onset cerebellar ataxia, peripheral neuropathy and pyramidal tract signs such as spasticity, abnormal reflexes and the loss of the ability to perform fine motor movements. The patient also revealed typical MRI findings, including bilaterally symmetrical, parallel, linear hypointensities in the pons on T2 and T2-fluid attenuated inversion recovery magnetic resonance image (MRI) sequences as well as yellow streaks of hypermyelinated fibers radiating from the edges of the optic fundi in the retina (unpublished data).

X-LINKED ATAXIA

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a recently recognized disorder. Fragile X syndrome is caused by FMR1 gene mutation, and Fragile X is the most common cause of genetic mental retardation. In Fragile X patients, the CGG trinucleotide sequence expands more than 200 times, and this area is usually hypermethylated, which usually leads to gene silencing and the absence of the Fragile X mental retardation protein (FMRP). The mental retardation is caused by the lack of FMRP in neurons in these patients. Expanded CGG sequences between 55 to 200 triplets are called premutations. These alleles produce increased levels of messenger RNA (FMR1 mRNA) that are up to eightfold higher than normal as well as a decreased range of FMRP. Individuals with a premutation do not manifest mental retardation, which is classical phenotype of Fragile X syndrome. However, these individuals exhibit a unique phenomenology typified by progressive ataxia and tremors, which is called FXTAS.

The only case of FXTAS was reported very recently in Korea [62]. A case of a 75-year-old male with resting tremors as the initial symptom was confirmed as FXTAS by detecting FMR1 gene permutations (136 repeats) using polymerase chain reaction and a southern blot. His MRI showed typical imaging features of T2 high signal intensity in the middle cerebellar peduncles as well as marked cerebellar and cerebral atrophy.

CLINICAL IMPLICATIONS

The diagnosis of hereditary ataxias should be considered based on ethnicity and region, and epidemiological data can help to determine if genetic sequencing should be performed. Although we cannot estimate the absolute prevalence and frequency of cerebellar ataxia, we suggest a rough estimate of the hereditary ataxia in Korean population. SCA2, 3, and 6 are the major disorders among the dominant SCAs in Korea. Overall, SCA2 is the most common cause of inherited ataxia, regardless of the inheritance pattern. DRPLA is rare outside of Japan, but it is not uncommon in Korea. The reports of cerebellar ataxias with autosomal recessive and X-linked inheritance patterns have been extremely rare [63,64].

We need to address the algorithm for the diagnosis of hereditary ataxia in the Korean population. In cases without a family history, secondary causes include alcoholic cerebellar degeneration, vitamin deficiency, drugs, toxic materials, strokes, tumors, infections, autoimmune diseases, paraneoplastic syndrome or demyelinating disease. Ataxias with secondary causes usually have an acute or subacute-onset and rapid progression. After ruling out the secondary causes of ataxia, a follow-up period is needed to confirm the diagnosis of MSA or sporadic adult onset ataxia with unknown origin (SAOA). Another point that we should consider is the ambiguity of the family history in genetic ataxias. In previous studies, a considerable number of patients who had the expanded pathological allele had a negative family history. Therefore, even if the patients have an inaccurate, ambiguous or negative family history, hereditary ataxia should be considered. One more important point to remember is that patients with SCA6 may not have a family history. The age of onset in SCA6 is higher than other types of SCAs. Early deaths or inappropriate diagnoses of parents are important factors to consider, and a de novo mutation may be another possibility.

Additionally, screening of SCA genes in patients with adult-onset chronic progressive cerebellar ataxia (who do not meet the criteria for the MSA-cerebellar type) would be needed regardless of family history, even if there were a less conclusive family history for confirming the inheritance pattern and overall detection rate of ADCA.

For early onset progressive ataxia (< 30 years), even though the patients do not require a family history, we should consider a possibility of hereditary ataxia, especially for ARCA. When ARCA is suspected, fundus examination and careful physical examination should be performed to find telangiectasia, xanthoma, limb deformity or retinitis pigmentosa. Additionally, we should find the clues by performing blood smears as well as tests for vitamin E, alpha-fetoprotein, cholesterol, thyroid function, immunological disorders, lactate/pyruvate, nerve conduction and brain MRI. If clinical or laboratory clues indicate specific disease, genetic sequencing is needed to confirm the diagnosis.

Unless certain suggestive clinical signs are shown, we emphasize that the screening for SCAs is recommended because of the high rate of SCA in the Korean population.

In cases with autosomal dominant inheritance patterns, clinical features become evident at approximately 35 years of age. SCA1, 2, 3, 6, 7, 8, and 17, which are most frequent subtypes in Korea, should be screened for first. If the results of those tests are negative, careful follow-up is needed to find evidence of MSA or SAOA.

It is true that ARCA is rare in Korea. Most centers in Korea perform screenings for the SCA and DRPLA gene for patients with adult-onset chronic progressive ataxia, and the possibility of underestimation for ARCA cannot be excluded. The paucity of full sequencing for ARCA and homogeneous genetic background might explain the rarity of ARCA in Korea. Awareness of the variable clinical features of ARCA (Table 3) might be helpful for clinicians when selecting candidates for further genetic evaluations. Case control studies and epidemiological studies, including genetic sequencing of ARCA, are needed in Korea.

Clinical, laboratory and radiological clues for the diagnosis of autosomal recessive cerebellar ataxias

The availability of novel genetic technologies for both research and diagnostic laboratories is rapidly developing, and this advance will facilitate rapid progress in this field. In the near future, more efficient diagnosis and the identification of many novel forms of ataxic diseases are expected.

Notes

Conflicts of Interest

The authors have no financial conflicts of interest.

Acknowledgements

This work was supported by a Samsung Medical Center grant (SMO1131541 and CB13152).

We are grateful to Prof. Seong-Beom Koh, Han-Joon Kim, Kyum-Yil Kwon, and Dr. Gwanhee Ehm for providing information about rare cases.

References

1. Brusse E, Maat-Kievit JA, van Swieten JC. Diagnosis and management of early- and late-onset cerebellar ataxia. Clin Genet 2007;71:12–24.
2. Fogel BL, Perlman S. Clinical features and molecular genetics of autosomal recessive cerebellar ataxias. Lancet Neurol 2007;6:245–257.
3. Holmes G. An attempt to classify cerebellar disease, with a note on Marie’s hereditary cerebellar ataxia. Brain 1907;30:545–567.
4. Greenfield JG. The Spinocerebellar Degenerations Spring-field, IL: Charles C. Thomas; 1954.
5. Harding AE. Classification of the hereditary ataxias and paraplegias. Lancet 1983;1:1151–1155.
6. Jayadev S, Bird TD. Hereditary ataxias: overview. Genet Med 2013;15:673–683.
7. Klockgether T. Update on degenerative ataxias. Curr Opin Neurol 2011;24:339–345.
8. Basu P, Chattopadhyay B, Gangopadhaya PK, Mukherjee SC, Sinha KK, Das SK, et al. Analysis of CAG repeats in SCA1, SCA2, SCA3, SCA6, SCA7 and DRPLA loci in spinocerebellar ataxia patients and distribution of CAG repeats at the SCA1, SCA2 and SCA6 loci in nine ethnic populations of eastern India. Hum Genet 2000;106:597–604.
9. Maruyama H, Izumi Y, Morino H, Oda M, Toji H, Nakamura S, et al. Difference in disease-free survival curve and regional distribution according to subtype of spinocerebellar ataxia: a study of 1,286 Japanese patients. Am J Med Genet 2002;114:578–583.
10. Nagaoka U, Suzuki Y, Kawanami T, Kurita K, Shikama Y, Honda K, et al. Regional differences in genetic subgroup frequency in hereditary cerebellar ataxia, and a morphometrical study of brain MR images in SCA1, MJD and SCA6. J Neurol Sci 1999;164:187–194.
11. Pujana MA, Corral J, Gratacòs M, Combarros O, Berciano J, Genís D, et al. Spinocerebellar ataxias in Spanish patients: genetic analysis of familial and sporadic cases. The Ataxia Study Group. Hum Genet 1999;104:516–522.
12. Ranum LP, Lundgren JK, Schut LJ, Ahrens MJ, Perlman S, Aita J, et al. Spinocerebellar ataxia type 1 and Machado-Joseph disease: incidence of CAG expansions among adult-onset ataxia patients from 311 families with dominant, recessive, or sporadic ataxia. Am J Hum Genet 1995;57:603–608.
13. Durr A. Autosomal dominant cerebellar ataxias: polyglutamine expansions and beyond. Lancet Neurol 2010;9:885–894.
14. Tsoi H, Yu AC, Chen ZS, Ng NK, Chan AY, Yuen LY, et al. A novel missense mutation in CCDC88C activates the JNK pathway and causes a dominant form of spinocerebellar ataxia. J Med Genet 2014;51:590–595.
15. Cadieux-Dion M, Turcotte-Gauthier M, Noreau A, Martin C, Meloche C, Gravel M, et al. Expanding the clinical phenotype associated with ELOVL4 mutation: study of a large French-Canadian family with autosomal dominant spinocerebellar ataxia and erythrokeratodermia. JAMA Neurol 2014;71:470–475.
16. Storey E. Genetic cerebellar ataxias. Semin Neurol 2014;34:280–292.
17. Stevanin G, Dürr A, Brice A. Clinical and molecular advances in autosomal dominant cerebellar ataxias: from genotype to phenotype and physiopathology. Eur J Hum Genet 2000;8:4–18.
18. Pearson CE, Nichol Edamura K, Cleary JD. Repeat instability: mechanisms of dynamic mutations. Nat Rev Genet 2005;6:729–742.
19. Moseley ML, Zu T, Ikeda Y, Gao W, Mosemiller AK, Daughters RS, et al. Bidirectional expression of CUG and CAG expansion transcripts and intranuclear polyglutamine inclusions in spinocerebellar ataxia type 8. Nat Genet 2006;38:758–769.
20. Chen WL, Lin JW, Huang HJ, Wang SM, Su MT, Lee-Chen GJ, et al. SCA8 mRNA expression suggests an antisense regulation of KLHL1 and correlates to SCA8 pathology. Brain Res 2008;1233:176–184.
21. van Gaalen J, Giunti P, van de Warrenburg BP. Movement disorders in spinocerebellar ataxias. Mov Disord 2011;26:792–800.
22. Giunti P, Sabbadini G, Sweeney MG, Davis MB, Veneziano L, Mantuano E, et al. The role of the SCA2 trinucleotide repeat expansion in 89 autosomal dominant cerebellar ataxia families. Frequency, clinical and genetic correlates. Brain 1998;121(Pt 3):459–467.
23. Ross OA, Rutherford NJ, Baker M, Soto-Ortolaza AI, Carrasquillo MM, DeJesus-Hernandez M, et al. Ataxin-2 repeat-length variation and neurodegeneration. Hum Mol Genet 2011;20:3207–3212.
24. Van Damme P, Veldink JH, van Blitterswijk M, Corveleyn A, van Vught PW, Thijs V, et al. Expanded ATXN2 CAG repeat size in ALS identifies genetic overlap between ALS and SCA2. Neurology 2011;76:2066–2072.
25. Lima L, Coutinho P. Clinical criteria for diagnosis of Machado-Joseph disease: report of a non-Azorena Portuguese family. Neurology 1980;30:319–322.
26. Kim JS, Kim JS, Youn J, Seo DW, Jeong Y, Kang JH, et al. Ocular motor characteristics of different subtypes of spinocerebellar ataxia: distinguishing features. Mov Disord 2013;28:1271–1277.
27. Lee JY, Lee WW, Kim JS, Kim HJ, Kim JK, Jeon BS. Perverted head-shaking and positional downbeat nystagmus in patients with multiple system atrophy. Mov Disord 2009;24:1290–1295.
28. David G, Dürr A, Stevanin G, Cancel G, Abbas N, Benomar A, et al. Molecular and clinical correlations in autosomal dominant cerebellar ataxia with progressive macular dystrophy (SCA7). Hum Mol Genet 1998;7:165–170.
29. Rolfs A, Koeppen AH, Bauer I, Bauer P, Buhlmann S, Topka H, et al. Clinical features and neuropathology of autosomal dominant spinocerebellar ataxia (SCA17). Ann Neurol 2003;54:367–375.
30. Nagafuchi S, Yanagisawa H, Sato K, Shirayama T, Ohsaki E, Bundo M, et al. Dentatorubral and pallidoluysian atrophy expansion of an unstable CAG trinucleotide on chromosome 12p. Nat Genet 1994;6:14–18.
31. Tsuji S. Dentatorubral-pallidoluysian atrophy. Handb Clin Neurol 2012;103:587–594.
32. Ikeuchi T, Koide R, Tanaka H, Onodera O, Igarashi S, Takahashi H, et al. Dentatorubral-pallidoluysian atrophy: clinical features are closely related to unstable expansions of trinucleotide (CAG) repeat. Ann Neurol 1995;37:769–775.
33. Brunetti-Pierri N, Wilfong AA, Hunter JV, Craigen WJ. A severe case of dentatorubro-pallidoluysian atrophy (DRPLA) with microcephaly, very early onset of seizures, and cerebral white matter involvement. Neuropediatrics 2006;37:308–311.
34. Yoon WT, Youn J, Cho JW. Is cerebral white matter involvement helpful in the diagnosis of dentatorubral-pallidoluysian atrophy? J Neurol 2012;259:1694–1697.
35. Ruano L, Melo C, Silva MC, Coutinho P. The global epidemiology of hereditary ataxia and spastic paraplegia: a systematic review of prevalence studies. Neuroepidemiology 2014;42:174–183.
36. van de Warrenburg BP, Sinke RJ, Verschuuren-Bemelmans CC, Scheffer H, Brunt ER, Ippel PF, et al. Spinocerebellar ataxias in the Netherlands: prevalence and age at onset variance analysis. Neurology 2002;58:702–708.
37. Rosenberg RN. Machado-Joseph disease: an autosomal dominant motor system degeneration. Mov Disord 1992;7:193–203.
38. de Castilhos RM, Furtado GV, Gheno TC, Schaeffer P, Russo A, Barsottini O, et al. Spinocerebellar ataxias in Brazil-- frequencies and modulating effects of related genes. Cerebellum 2014;13:17–28.
39. Vale J, Bugalho P, Silveira I, Sequeiros J, Guimarães J, Coutinho P. Autosomal dominant cerebellar ataxia: frequency analysis and clinical characterization of 45 families from Portugal. Eur J Neurol 2010;17:124–128.
40. Schöls L, Amoiridis G, Büttner T, Przuntek H, Epplen JT, Riess O. Autosomal dominant cerebellar ataxia: phenotypic differences in genetically defined subtypes? Ann Neurol 1997;42:924–932.
41. Tang B, Liu C, Shen L, Dai H, Pan Q, Jing L, et al. Frequency of SCA1, SCA2, SCA3/MJD, SCA6, SCA7, and DRPLA CAG trinucleotide repeat expansion in patients with hereditary spinocerebellar ataxia from Chinese kindreds. Arch Neurol 2000;57:540–544.
42. Basri R, Yabe I, Soma H, Sasaki H. Spectrum and prevalence of autosomal dominant spinocerebellar ataxia in Hokkaido, the northern island of Japan: a study of 113 Japanese families. J Hum Genet 2007;52:848–855.
43. Polo JM, Calleja J, Combarros O, Berciano J. Hereditary ataxias and paraplegias in Cantabria, Spain. An epidemiological and clinical study. Brain 1991;114(Pt 2):855–866.
44. Leone M, Bottacchi E, D’Alessandro G, Kustermann S. Hereditary ataxias and paraplegias in Valle d’Aosta, Italy: a study of prevalence and disability. Acta Neurol Scand 1995;91:183–187.
45. Saleem Q, Choudhry S, Mukerji M, Bashyam L, Padma MV, Chakravarthy A, et al. Molecular analysis of autosomal dominant hereditary ataxias in the Indian population: high frequency of SCA2 and evidence for a common founder mutation. Hum Genet 2000;106:179–187.
46. Orozco G, Estrada R, Perry TL, Araña J, Fernandez R, Gonzalez-Quevedo A, et al. Dominantly inherited olivopontocerebellar atrophy from eastern Cuba. Clinical, neuropathological, and biochemical findings. J Neurol Sci 1989;93:37–50.
47. Matsumura R, Futamura N, Ando N, Ueno S. Frequency of spinocerebellar ataxia mutations in the Kinki district of Japan. Acta Neurol Scand 2003;107:38–41.
48. Joo BE, Lee CN, Park KW. Prevalence rate and functional status of cerebellar ataxia in Korea. Cerebellum 2012;11:733–738.
49. Kim JY, Park SS, Joo SI, Kim JM, Jeon BS. Molecular analysis of Spinocerebellar ataxias in Koreans: frequencies and reference ranges of SCA1, SCA2, SCA3, SCA6, and SCA7. Mol Cells 2001;12:336–341.
50. Lee WY, Jin DK, Oh MR, Lee JE, Song SM, Lee EA, et al. Frequency analysis and clinical characterization of spinocerebellar ataxia types 1, 2, 3, 6, and 7 in Korean patients. Arch Neurol 2003;60:858–863.
51. Jin DK, Oh MR, Song SM, Koh SW, Lee M, Kim GM, et al. Frequency of spinocerebellar ataxia types 1,2,3,6,7 and dentatorubral pallidoluysian atrophy mutations in Korean patients with spinocerebellar ataxia. J Neurol 1999;246:207–210.
52. Kim JM, Shin S, Kim JY, Joo SI, Park SS, Kim JW, et al. Spinocerebellar ataxia type 2 in seven Korean families: CAG trinucleotide expansion and clinical characteristics. J Korean Med Sci 1999;14:659–664.
53. Kim HJ, Jeon BS, Lee WY, Chung SJ, Yong SW, Kang JH, et al. SCA in Korea and its regional distribution: a multicenter analysis. Parkinsonism Relat Disord 2011;17:72–75.
54. Heo JH, Bang OY, Moon JS, Sunwoo IN, Kim TS. A case of friedreich’s ataxia with optic atrophy as an initial? clinical manifestation. Korean J Neurology 1994;12:562–565.
55. Lee SA, Sunwoo IN, Kim KW. Electrophysiological studies in a case of friedreich’s ataxia. Korean J Neurology 1986;4:137–141.
56. Jeong H, Huh HJ, Youn J, Kim JS, Cho JW, Ki CS. Ataxiatelangiectasia with novel splicing mutations in the ATM gene. Ann Lab Med 2014;34:80–84.
57. Huh HJ, Cho KH, Lee JE, Kwon MJ, Ki CS, Lee PH. Identification of ATM mutations in Korean siblings with ataxiatelangiectasia. Ann Lab Med 2013;33:217–220.
58. Song MH, Kim EJ, Sung TJ, Shin SH, Lee KH, Kim HD. A case of progressive elevation of serum gamma-GTP level in ataxia-telangiectasia. J Korean Child Neurol Soc 2006;14:363–368.
59. Kang DW, Ahn SS, Jeon BS. A case of ataxia telangiectasia. J Korean Neurol Assoc 1997;15:895–899.
60. Hwang SY, Lee KH, Ahn JI. Cerebrotendinous xanthomatosis. J Dermatol 1990;17:115–119.
61. Suh S, Kim HK, Park HD, Ki CS, Kim MY, Jin SM, et al. Three siblings with Cerebrotendinous Xanthomatosis: a novel mutation in the CYP27A1 gene. Eur J Med Genet 2012;55:71–74.
62. Ehm G, Yang HJ, Kim HJ, Jeon BS. The first case report of fragile X-associated tremor ataxia syndrome in the Republic of Korea. Neurology Asia 2014;19:99–103.
63. Kim HS. Social integration and heath policy issues for international marriage migrant women in South Korea. Public Health Nurs 2010;27:561–570.
64. HUGO Pan-Asian SNP Consortium, Abdulla MA, Ahmed I, Assawamakin A, Bhak J, Brahmachari SK, et al. Mapping human genetic diversity in Asia. Science 2009;326:1541–1545.

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Table 1.

SCA: distinguishing features and molecular genetics

Disorder Distinguishing features Gene/locus Protein or types of mutation
SCA1 Pyramidal signs, peripheral neuropathy ATXN1 CAG repeat, ataxin-1
SCA2 Slow saccades; less often myoclonus, areflexia ATXN2 CAG repeat, ataxin-2
SCA3 Slow saccades, persistent stare, extrapyramidal signs, peripheral neuropathy ATXN3 CAG repeat, ataxin-3 (MJD1)
SCA4 Sensory neuropathy 16q22.1
SCA5 Early onset but slow progression SPTBN2 Beta III spectrin
SCA6 May have very late onset, mild, may lack family history, nystagmus CACNA1A CAG repeat, alpha 1A P/Q calcium channel subunit
SCA7 Macular degeneration ATXN7 CAG repeat, ataxin-7
SCA8 Mild disease ATXN8/ATXN8OS CTG*CAG repeat
SCA9 Not assigned
SCA10 Generalized or complex partial seizures ATXN10 ATTCT repeat, ataxin-10
SCA11 Mild disease TTBK2 Tau tubulin kinase-2
SCA12 Tremor, dementia PPP2R2B CAG repeat in 5ʼ region, protein phosphatase 2A
SCA13 Mental retardation KCNC3 Voltage gated potassium channel KCNC3
SCA14 Intermittent myoclonus with early onset disease PRKCG Protein kinase C gamma
SCA15/16 Slowly progressive ITPR1 Inositol 1,4,5-triphosphate receptor 1
SCA17 Gait ataxia, dementia TBP CAG repeats, TATA binding protein
SCA18 Pyramidal signs, weakness, sensory axonal neuropathy 7q22-q32
SCA19/22 Predominantly cerebellar syndrome, sometimes with cognitive impairment or myoclonus KCND3 Voltage-gated potassium channel Kv4.3
SCA20 Palatal tremor and dysphonia 11q12
SCA21 Extrapyramidal signs 7p21.3-p15.1
SCA23 Distal sensory deficits PDYN Prodynorphin
SCA24 Recessive inheritance; redesignated as SCAR4 1p36
SCA25 Sensory neuropathy, facial tics, gastrointestinal symptoms 2p21-p13
SCA26 Pure cerebellar ataxia 19p13.3
SCA27 Cognitive impairment FGF14 Fibroblast growth factor 14
SCA28 Ophthalmoparesis and ptosis AFG3L2 Catalytic subunit of the mitochondrial AAA protease
SCA29 Early onset, non-progressive ataxia; may be an allelic variant of SCA15 3p26
SCA30 Slowly progressive, relatively pure ataxia 4q34.3-q35.1
SCA31 Decreased muscle tone BEAN (TGGAA) n repeat
SCA32 Cognitive impairment, affected males with azoospermia and testicular atrophy 7q32-q33
SCA33 Not assigned
SCA34 Skin lesions consisting of papulosquamous erythematous ichthyosiform plaques 6p12.3-q16.2
SCA35 Late onset, slowly progressive gait and limb ataxia TGM6 Transglutaminase 6
SCA36 Late onset, truncal ataxia, dysarthria, variable motor neuron disease, and sensorineural hearing loss NOP56 GGCCTG repeat
SCA37 Late onset, falls, dysarthria, clumsiness, abnormal vertical eye movements 1p32
SCA38 Adult onset, axonal neuropathy ELOVL5
SCA40 Adult onset, brisk reflexed, spasticity CCDC88C

SCA: spinocerebellar ataxias, CAG: coronary angiography.

Table 2.

Reports of cerebellar ataxia with an autosomal recessive inheritance pattern in Korea

Disease Gene/product Case Clinical manifestations Mutation confirmed
FRDA FXN/frataxin Heo et al. [54] Optic atrophy as the initial clinical manifestation No
Lee et al. [55] Hearing difficulty, gait ataxia, scoliosis, proprioceptive loss No
AT ATM/ATM protein Jeong et al. [56] Early onset ataxia, oculomotor apraxia, polyneuropathy, telangiectasia Yes
Huh et al. [57] Early onset ataxia, oculomotor apraxia, telangiectasia Yes
Song et al. [58] Early onset ataxia, frequent infections, telangiectasia No
Kang et al. [59] Early onset ataxia, oculomotor apraxia, dysarthria, telangiectasia No
CTX CYP27A1/sterol-27 hydroxylase Hwang et al. [60] Ataxia, xanthomas, dementia, cranial nerve palsy, pyramidal signs, cataracts No
Suh et al. [61] Xanthomas, cataract, osteopenia, mental retardation, ataxia, neuropathy Yes
ARSACS SACS/sacsin Unpublished Early onset ataxia, spasticity, distal amyotrophy with foot deformity Yes
FXTAS FMR1/FMRP protein Ehm et al. [62] Gait ataxia, parkinsonism, mood disorder, high signal in MCP Yes

FRDA: Friedreich’s ataxia, AT: ataxia telangiectasia, CTX: cerebrotendinous xanthomatosis, ARSACS: autosomal recessive spastic ataxia of Charlevoix-Saguenay, FXTAS: Fragile X-associated tremor/ataxia syndrome.

Table 3.

Clinical, laboratory and radiological clues for the diagnosis of autosomal recessive cerebellar ataxias

Diagnosis Gene/protein Age of onset Clinical, laboratory, and radiologic clues for diagnosis
Friedreich ataxia FXN/frataxin 1st–2nd decade Areflexia with Babinski reflex, skeletal deformity, cardiomyopathy, DM, sensory neuropathy, no cerebellar atrophy on brain MRI
Ataxia with vitamin E deficiency ATTP/α-tocopherol transfer protein 2–50 years Decreased vitamin E, retinitis pigmentosa, no cerebellar atrophy on brain MRI, sensory neuropathy
Abetalipoproteinemia MTP/microsomal triglyceride transfer protein From birth Abnormal in lipoprotein, no cerebellar atrophy on brain MRI, decreased vitamin E, sensory neuropathy
Mitochondrial recessive ataxia syndrome POLG/polymerase γ Childhood to young adult Neuropathy, deafness, epilepsy, dysarthria, nystagmus
Ataxia telangiectasia ATM/ataxia telangiectasia mutated < 5 years Telangiectasia, chorea, dystonia, immunodeficiency, increased α-fetoprotein, sensorimotor neuropathy
AOA 1 APTX/aprataxin Infancy Oculomotor apraxia, chorea, dystonia, sensorimotor neuropathy, decreased albumin level, increased LDL cholesterol level
AOA 2 SETX/senataxin 7–25 years Oculomotor apraxia, axonal sensorimotor neuropathy, increased serum α-fetoprotein
ARSACS SACS/sacsin Childhood Spastic ataxia, sensorimotor neuropathy, hypertrophic myelinated fibers in the fundus, linear hypointensities in the Pons
CTX CYP27A1/CYP27A1 Childhood to young adult Xanthomas, spastic ataxia, mental retardation, white matter change, premature cataract, sensorimotor neuropathy
Refsum disease Pex7, Pex10, PHYH/peroxin-7, peroxin-10, phytanoyl-CoA hydroxylase 10–20 years Sensorimotor neuropathy, retinopathy, deafness, ichthyosis, no cerebellar atrophy on brain MRI

AOA 1: ataxia with oculomotor apraxia type 1, LDL: low-density lipoprotein, AOA 2: ataxia with oculomotor apraxia type 2, ARSACS: autosomal recessive spastic ataxia of Charlevoix-Saguenay, CTX: cerebrotendinous xanthomatosis.