ATXN2 and spinocerebellar ataxia type 2: For example, Dewan and colleagues identified pathogenic HTT repeat expansions in patients diagnosed with FTD/ALS neurodegenerative disorders with mutations in TDRPH (Dewan et al., 2021), while polyQ expansions in the ATXN2 gene, that are normally associated with the onset of SCA2, have been observed in some forms of ALS (van den Heuvel et al., 2014).