TRPA1 and Alzheimer disease: Although treatment of moderate-to-severe AD has entered a new era centered on biologic agents, interindividual differences in the expression of key neuroimmune genes such as IL-31, MRGPRX2, TRPA1, NGF, and CGRP contribute to molecular heterogeneity that is closely associated with the intensity of pruritus and disease chronicity, and these differences significantly affect patients’ responses to therapy (187).