The GGGGCC large repeat expansions (from 250 up to > 3000 repeats) present in the first intron of the C9ORF72 gene and coding for poly‐dipeptides [poly(GA), poly(GP), poly(GR), poly(PR) and poly(PA)] have been identified in patients suffering from ALS with or without frontotemporal dementia (FTD).99, 100. Here, C9orf72 is linked to frontotemporal dementia.