Finally, we separated the presence of WMH in GRN mutation carriers into three groups (none/mild, moderate and severe loads) as is often done in other pathologies involving WMH such as multiple sclerosis, with a threshold at 1000 mm3 and 2500mm3 in a mean TIV of 1400ml (corresponding to an occupancy of 0.07% and 0.18% of the TIV) (Table 5). This evidence concerns the gene GRN and multiple sclerosis.