Moreover, while TREM2 research has undoubtedly offered new insight into the underlying pathological processes of AD, its mutation, along with mutations in Presenilin 1 (PS1), Presenilin 2 (PS2), and Amyloid precursor protein (APP) account for <5% of all AD cases (National Institute of Aging, 2011). Here, TREM2 is linked to Alzheimer disease.