High-penetrance inherited pathogenic mutations in C9ORF72, GRN, MAPT, TARDBP, and FUS have been implicated in ~20% of patients with FTLD and ALS-FTLD (2), with the GGGGCC hexanucleotide repeat expansion (HRE) in C9ORF72 being the most common (3). Here, C9orf72 is linked to amyotrophic lateral sclerosis.