C9orf72 and frontotemporal dementia: C9orf72-specific imaging features of patients with ALS and FTD have been described in comparison to sporadic patients with the same clinical phenotype (Bede et al., 2013a, Byrne et al., 2012, Rohrer et al., 2015b, Whitwell et al., 2015, Bocchetta et al., 2016).