The TREM2*R47H mutation triples the carrier’s likelihood of Alzheimer’s disease (Allen et al., 2016; Cacace et al., 2016; Wang et al., 2018; Logsdon et al., 2019; Andrews et al., 2020; Bellenguez et al., 2020). The gene discussed is TREM2; the disease is early-onset autosomal dominant Alzheimer disease.