TREM2 and frontotemporal dementia: Here, in a multiple single cases study, we aimed to compare cognitive, neuropsychiatric, and brain atrophy patterns in FTD patients (N = 42) with different genetic levels (G-FTD), including a) GR1: patients with mutations in different types of causative genes (MAPT, TARDBP, and TREM2), b) GR2: patients with variants in candidate genes potentially associated with FTD (tau Haplotypes H1 and H2 and variants of APOE including ε2, ε3, ε4), and c) S-FTD (GR3): patients with sporadic FTD.