C9orf72 and Alzheimer disease: Examples include the links between immune system disruption and AD, protein aggregation underlying AD, PD and prion disease, the commonality in C9orf72 hexanucleotide repeat expansions between forms of frontotemporal degeneration (FTD) and amyotrophic lateral sclerosis (ALS) and the high prevalence of vascular disease that includes risk factors and clinical expression of AD (Goedert, 2015; Rohrer et al., 2015; Colonna and Wang, 2016).