This hypometabolism pre-dates dementia in FTD linked Granulin (GRN) mutant carriers [12], spreads as disease progresses [13] and in Microtubule-Associated Protein Tau (MAPT) -linked FTD patients closely maps to areas of toxic MAPT accumulation [14], suggesting it closely tracks disease development. Here, GRN is linked to frontotemporal dementia.