ATXN2 and Parkinson disease: SCA2 is an autosomal dominant disease caused by abnormal amplification of CAG (trinucleotide cytosine-adenine-guanine deoxyribonucleic acid) in the ATXN2 (12q23-q24.1) gene, which is diagnosed according to the criteria of SCA2.[4] The usual range of CAG repeats is 11 to 31,[5] with a pathogenic range of 34 to 200 repeats.[2] ATXN2 mutations cause Parkinsonism,[6] which are characteristic of bradykinesia, rigidity, tremor, etc according to the criteria of MDS.[7] In 2007, Kim et al[8] suggested that abnormal amplification of CAG in ATXN2 gene may be the Parkinsonism's causative mechanism.