C9orf72 and amyotrophic lateral sclerosis: These expansions located in the 5′UTR (or first intron depending on the isoform) of C9ORF72 cause a dominant disorder characterized by frontotemporal dementia, amyotrophic lateral sclerosis, or the association of both at the individual level and/or within families (ALS/FTD, MIM #105550).