The R47H and other variants of triggering receptors on myeloid cells (TREM)‐2, which result in loss of TREM2 function, are strong risk factors for PD.24, 25, 26 Activated microglia in the SN proliferate and produce reactive oxygen species and pro‐inflammatory cytokines, resulting in progressive degeneration of DA neurons in PD.27, 28 TREM2 may regulate microglial response and phagocytosis. This evidence concerns the gene TREM2 and Parkinson disease.