MRGPRX2 and Alzheimer disease: Due to the expression of MRGPRX2 in connective tissue mast cells of the skin [35], Wang et al. proposed a possible role of MRGPRX2 in AD: while MRGPRX2-activated mast cells release inflammatory cellular contents that act on sensory nerves, neuropeptides from sensory fibers promote mast cell activity via MRGPRX2 in the skin.