Patients with the C9orf72 mutation can present with a clinical phenotype of FTD, ALS, or a combination of ALS and FTD symptoms, even within the same family (Kaivorinne et al., 2013, Hsiung et al., 2012, Rohrer et al., 2015a). Here, C9orf72 is linked to amyotrophic lateral sclerosis.