The results of the present study clearly demonstrate that blood levels of PGRN are greatly reduced in patients bearing GRN mutations compared with others with FTLD, those with AD, or control subjects, and therefore support previous findings (Finch et al., 2009; Ghidoni et al., 2009; Hsiung et al., 2011, Sleegers et al., 2009). This evidence concerns the gene GRN and Alzheimer disease.