C9orf72 and frontotemporal dementia: Mutation‐positive converters pooled across genetic subgroups (n = 19; C9orf72 = 7, GRN = 8, MAPT = 4) demonstrated a significant decline in perfusion from baseline based on their last follow‐up scan compared to presymptomatic carriers who went beyond their expected age of symptom onset (n = 22; C9orf72 = 6, GRN = 14, MAPT = 2) without showing symptoms or signs of FTD (Table 5).