C9orf72 and amyotrophic lateral sclerosis: Although often clinically indistinguishable in established symptomatic disease, SOD1 ALS is notable in lacking the characteristic neuronal and glial cytoplasmic inclusions of TDP‐43 that are found in 97% of all other cases of ALS (and 50% of FTD), including those mediated by C9orf72 (Mackenzie et al. 2007).