A 3.4-fold increase in TREM2 mRNA levels was observed in the hippocampus of AD cases compared to controls (mean ± SD mRNA levels in AD versus controls: 6.65 ± 4.30 % versus 1.73 ± 1.24 %; p = 1.1E-05) (Fig. 1a). This evidence concerns the gene TREM2 and Alzheimer disease.