In addition to APOE, recent genome-wide association studies (GWAS) have identified more than 20 additional susceptibility loci associated with AD, including rare coding variants of TREM2 that confer AD risk comparable to that of APOE4 carriers (Benitez and Cruchaga, 2013; Guerreiro and Hardy, 2013; Guerreiro et al., 2013). This evidence concerns the gene TREM2 and Alzheimer disease.