GRN and Gliosis: White matter changes such as gliosis and demyelination have long been observed in histological studies of FTD (Englund & Brun, 1987) and several groups have observed significant WMH on MRI brain scans of GRN mutation carriers with FTD who lack vascular risk factors (Caroppo et al., 2014; Ameur et al., 2016; Kelley et al., 2009; Le Ber et al., 2008; Paternicò et al., 2016; Pietroboni et al., 2011; Sudre et al., 2017).