C9orf72 and frontotemporal dementia: In a study published by the Mesulam working group [19], where targeted sequencing was performed for the main genes responsible for both AD and frontotemporal dementia (APP, TARDBP, FUS, GRN, MAPT, PSEN1, PSEN2, C9orf72, MAPT A152T, TREM2 R47H, APOE) in 403 cases of APP, they apparently found that 14 (3.5%) cases were carriers of pathological variants: 4 showed expansions of the C9orf72 gene, 9 in the GRN gene, and 1 in the TAR DNA-binding protein (TARDBP) gene.