C9orf72 and frontotemporal dementia: As much as 85% of FTD cases caused by C9orf72 expansions are associated with the bvFTD subtype [31], while 22.31% of C9orf72 expansion carriers display additional degeneration of motor neurons or FTLD with amyotrophic lateral sclerosis (FTLD-ALS) [31,32].