C9orf72 and amyotrophic lateral sclerosis: FTLD-FUS/FET pathology in FTD differs in that it is composed of hypomethylated FUS with EWS and TAF15 but not transportin-1, as in ALS.19 While FTD-causative FUS mutations are very rare,20,21 FUS pathology has been reported in a FTD patient with FUS mutation.22 At the ends of the spectrum, SOD1 mutations occur with SOD1 aggregates in ALS23 and tau mutations with FTLD-tau.24 Finally, despite differing functions and clinical associations, both PGRN and C9ORF72 mutations exhibit TDP-43 pathology.