Previous studies have demonstrated that patients with null mutations in GRN display very low plasma progranulin levels compared with sporadic FTD (Finch et al., 2009, Ghidoni et al., 2008, Sleegers et al., 2009), and that this analysis is useful to identify carriers of mutation causing haploinsufficiency, independent of the clinical presentation (Carecchio et al., 2009). This evidence concerns the gene GRN and frontotemporal dementia.