C9orf72 and amyotrophic lateral sclerosis: Approximately 5 % of ALS cases are familial, and 70 % of these have mutations in C9ORF72, SOD1, TDP43 or FUS. In the majority of ALS cases, the cause of motor neuron degeneration is unknown, although a number of pathogenic processes, including excitotoxicity, oxidative stress, protein aggregation, mitochondrial dysfunction, dysregulation of the cytoskeleton and axonal transport, and inflammation are considered to play important roles [9].