However, when the CAG trinucleotide repeats in the ATXN2 gene are abnormally amplified to an intermediate length (>23), it can lead to ALS pathology [32,33,34]; when the CAG is further abnormally amplified (>33), it may cause spinocerebellar ataxia type 2 (SCA2) [35,36]. The gene discussed is ATXN2; the disease is spinocerebellar ataxia type 2.