GRN and frontotemporal dementia: Heterozygous mutations in GRN, a lysosomal localized protein, cause FTD and lead to biochemical changes characteristic of lysosomal storage diseases (Gotzl et al., 2014); with rare homozygous GRN mutations directly causing neuronal ceroid lipofuscinosis, a lysosomal storage disorder (Smith et al., 2012).