In order to understand the natural history of C9ORF72 related ALS in terms of measures of rate of progression, the investigators need to understand how the size of the hexanucleotide repeat expansion influences disease parameters. A C9ORF72-focused clinical trial defining an accurate historical control population, will be critical since there may not be enough subjects for a placebo controlled trial. To be ready for upcoming therapeutic trials, the investigators need to start the detailed characterization of the C9ORF72 patients immediately.