TREM2 and Dravet syndrome: We have identified two extended haplotypes in DS cohorts which are the TREM2-C, HLA-DR-G, Tau-H2, and ApoE-ɛ2 variants as being a protective haplotype (C-G-H2-ɛ2) and a high-risk or disease haplotype, the TREM2-T, HLA-DR-A, Tau-H1, and ApoE-ɛ4 (T-A-H1-ɛ4) (Table 2).