We hypothesized that pain and temperature symptoms would be over-represented in behavioural variant FTD and semantic dementia versus progressive non-fluent aphasia (PNFA) and Alzheimer’s disease, and more specifically, in patients with C9orf72 mutations versus other disease groups; and that behavioural variant FTD and semantic dementia have overlapping but differentiable symptom profiles characterized by blunted versus heightened pain and temperature responsiveness, respectively. This evidence concerns the gene C9orf72 and Alzheimer disease.