APOE and Alzheimer disease: The loss‐of‐function mutations in triggering receptor expressed on myeloid cells‐2 (TREM2) in microglia could also increase the risk of AD up to 4‐fold (Hall‐Roberts et al., 2020; Jin et al., 2014), similar to the risk increment of heterozygous ε4‐apolipoprotein E (APOE) (Gratuze et al., 2018).