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Frequency Analysis of Autosomal Dominant Cerebellar Ataxias in Taiwanese Patients and Clinical and Molecular Characterization of Spinocerebellar Ataxia Type 6
Bing-wen Soong, MD, PhD;
Yi-chun Lu, MS;
Kong-bung Choo, PhD;
Hsiang-ying Lee, MS
Arch Neurol. 2001;58:1105-1109.
Background Spinocerebellar ataxia (SCA) is a heterogeneous group of neurodegenerative
disorders. The mutational basis for most of these disorders is an expanded
CAG repeat sequence within the coding regions of the genes involved. The prevalence
of SCA in the ethnic Chinese on Taiwan remains unclear. Moreover, there has
been no report of SCA type 6 (SCA6) among Chinese people.
Objectives To characterize the prevalence of SCA in the ethnic Chinese on Taiwan,
and to specifically characterize Chinese patients with SCA6 in terms of clinical
and molecular features.
Patients and Methods Using a molecular approach, we investigated SCA in 74 Taiwanese families
with dominantly inherited ataxias and in 49 Taiwanese patients with sporadic
ataxias. Clinical and molecular features of SCA6 were further characterized
in 12 patients from 8 families and in 2 sporadic cases. Furthermore, the intragenic
polymorphic marker D19S1150 was amplified by polymerase
chain reaction to analyze for linkage disequilibrium.
Results Machado-Joseph disease–SCA3 was the most common type of autosomal
dominant SCA in the Taiwanese cohort, accounting for 35 cases (47.3%), followed
by SCA6 (8 [10.8%]), SCA2 (8 [10.8%]), SCA1 (4 [5.4%]), SCA7 (2 [2.7%]), dentatorubropallidoluysian
atrophy (1 [1.4%]), and SCA8 (0%). The genes responsible for 16 (21.6%) of
Taiwanese dominantly inherited SCA cases remain to be determined. Among the
49 patients with sporadic ataxias in the present series, 2 (4.1%) were found
to harbor SCA6 mutations. In the families with SCA6, we found significant
anticipation in the absence of genetic instability on transmission, indicating
that some other mechanism might account for the anticipation. The same frequent
allele of the intragenic DNA marker (D19S1150) was
shared by 7 of 10 Taiwanese families with SCA6.
Conclusions Although SCA6 has, so far, not been reported in mainland Chinese, we
found a geographic cluster of families with SCA6 on Taiwan. Genotyping studies
suggest a founder effect in the Taiwanese patients with SCA6.
From the Department of Neurology, National Yang-Ming University School
of Medicine (Dr Soong), The Neurological Institute (Dr Soong and Mss Lu and
Lee), and Department of Medical Research and Education, Taipei–Veterans
General Hospital (Dr Choo), Taipei, Taiwan, Republic of China.
Corresponding author and reprints: Bing-wen Soong, MD, PhD, the Neurological
Institute, Taipei–Veterans General Hospital, Taipei, Taiwan 112, Republic
of China (e-mail: bwsoong{at}vghtpe.gov.tw).
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