TREM2 and Alzheimer disease: Recently, it was reported that heterozygous mutations in the triggering receptor expressed on myeloid cells 2 (TREM2) increase the risk for AD, frontotemporal lobar degeneration, amyotrophic lateral sclerosis, and Parkinson's disease (Guerreiro et al, 2013; Jonsson et al, 2013; Rayaprolu et al, 2013; Borroni et al, 2014; Cady et al, 2014; Cuyvers et al, 2014; Colonna & Wang, 2016; Ulrich & Holtzman, 2016; Villegas‐Llerena et al, 2016).