C9orf72 and amyotrophic lateral sclerosis: A subset of TDP-43 proteinopathies can present in the context of rare genetic variants, such as hexanucleotide repeat expansion (HRE) in an intronic region of the C9orf72 gene (C9orf72 HRE) which accounts for around 10% of cases of ALS and FTD, and variants in the granulin precursor (GRN), which accounts for 5–10% of FTD caes [10–14].