C9orf72 and frontotemporal dementia: The two most common genetic causes of familial FTD with TDP-43 inclusions are heterozygous mutations in the gene encoding progranulin (GRN), which accounts for 5–20% of inherited FTD [5, 6]; and hexanucleotide repeat (GGGGCC) expansions in a non-coding region of the C9orf72 gene, accounting for approximately 20% of inherited FTD [7].