Clinical and molecular analyses of a Chinese spinocerebellar ataxia type 7 family that includes infantile - onset cases

Background: Spinocerebellar ataxia type 7 (SCA7) is a rare subtype of SCA in the Chinese population. To the best of our knowledge, no Chinese infantile-onset cases confi rmed by molecular analysis have been reported. Methods: Clinical and molecular analyses were performed in a Chinese family with several members clinically diagnosed with SCA7. Results: After molecular analysis of ATXN7, the father and his daughter were shown by the agarose gel electrophoresis analysis to have one expanded allele and one normal allele. DNA sequencing showed the diplotype CAG repeats in the father and daughter to be 50/11 and 189/10, respectively. Based on this result and observed clinical features, the daughter was diagnosed with an infantile-onset SCA7. Conclusion: This is the fi rst report of infantile-onset SCA7 in the Chinese population confi rmed by molecular analysis. Our data also indicate that life expectancy is longer for infantile-onset cases without multi-organ damage, compared to cases with multi-organ damage. Neurology Asia 2012; 17(2) : 121 – 126 Address correspondence to: Zhi-Ying Wu, MD, PhD, Department of Neurology and Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, 12 Wulumuqi Zhong Road, Shanghai 200040, China. Tel/Fax: +86 21 62483421, E-mail: [email protected] INTRODUCTION Spinocerebellar ataxia type 7 (SCA7) is associated with a variety of clinical manifestations, including progressive cerebellar ataxia, dysarthria and decreased visual acuity. Compared to other SCAs, impairment of color vision and the presence of pigmentary maculopathy are distinguishing clinical features of SCA7 patients. SCA7 is caused by expansions of CAG repeats located in exon 3 of the ATXN7 gene on chromosome 3p1421.1. The number of CAG repeats is within the range of 4-35 in normal individuals and 38-406 in SCA7 patients. In patients, the age of onset inversely correlates with the number of CAG repeats. Rare infantile-onset cases (defi ned as onset age less than 2 years) are characterized by CAG repeat numbers over 130. The frequency of SCA7 varies among ethnic groups. SCA7 is the most common subtype of SCAs in Sweden and Finland, but is rare in China. To our knowledge, only 8 SCA7 families and 1 sporadic SCA7 case have previously been reported for mainland Chinese. No molecularly confi rmed infantileonset case, however, has been previously reported. Here, we report the fi rst Chinese infantile-onset SCA7 case confi rmed by molecular analysis.