An intronic hexanucleotide repeat expansion in the C9ORF72 gene (GGGGCC) has recently been shown to be the genetic cause of chromosome 9p21-linked ALS-FTLD, and accounts for 30–40 % of familial ALS and a similar portion of familial FTLD, further linking these two neurodegenerative disorders [8, 38]. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.