Interestingly, Tau pathology has also been observed in some mixed amyotrophic lateral sclerosis (ALS)/FTD cases bearing GGGGCC expansions in C9ORF72, suggesting that some patients with nucleotide repeat expansions could develop a mixed pathology (Bieniek et al., 2013; King et al., 2013). Here, C9orf72 is linked to amyotrophic lateral sclerosis.