Through the use of a lesion segmentation algorithm adapted to segment WMH from 3D T1- and T2- weighted scans this study extends previous work on WMH in genetic FTD to show their presence in a symptomatic GRN mutation group only, and not in presymptomatic participants nor in those with MAPT or C9orf72 mutations. The gene discussed is C9orf72; the disease is frontotemporal dementia.