TREM2 and Alzheimer disease: The association at TREM2 p.(Arg47His) and AD has been replicated in multiple populations of European descent [28–35, 36•, 37, 38], and although the risk-effect sizes vary by cohort, cumulatively, the results suggest that TREM2 R47H is the largest genetic effector of sporadic AD after APOE ε4.