ATXN2 usually contains a repeat structure with 22 or 23 triplets coding for glutamine and the (CAG)8CAA(CAG)4CAA(CAG)8 sequence; expansion of this domain to a size ≥34 triplets with a pure CAG sequence primarily causes autosomal dominant SCA2 [32], while ATXN2 expansions with CAA interruptions were observed as the cause of Levo-dopa responsive Parkinson’s disease [33]. This evidence concerns the gene ATXN2 and Parkinson disease.