Interestingly, pathogenic mutations in PSEN1, GRN, and MAPT genes were found in 2.3% of the screened cases, suggesting that pathogenic mutations or risk variants in MAPT and in GRN are as frequent in clinical AD cases as mutations in APP, PSEN1, and PSEN2 (Jin et al., 2012). Here, GRN is linked to Alzheimer disease.