One of these, TREM2 (triggering receptor expressed on myeloid cells 2), has an AD-associated risk allele (R47H) with an effect size in AD similar to that of ApoE4 (odds ratio 2.90–5.05) (Guerreiro et al., 2013b, Jonsson et al., 2013). The gene discussed is APOE; the disease is Alzheimer disease.