Amyotropic lateral sclerosis (ALS) is the commonest form of motor neuron disease, with some cases caused by mutations in the C9ORF72 gene. At our tertiary neurosciences clinic, we compared a group of ALS patients with the C9ORF72 mutation to a group without the mutation. Patients with the C9ORF72 mutation were more likely to present with cognitive impairment and difficulties in swallowing and speech. There were also differences between the groups when we examined the nervous system. Our findings highlight some unique features of C9ORF72-positive ALS, which is important for future medical treatments that may be able to target this gene. (By Dr Laura White, https://jmg.bmj.com/content/early/2023/05/11/jmg-2022-109016 )