These mediators, including substance P, total IgE, CCL24, tryptase, IL-31, IL-33, and GRP, although not exclusively linked to MCs, can function as either activators of MCs (substance P, IgE, IL-33, CCL24, and GRP) or as mediators released by MCs (tryptase, IL-31) [35–38], indicating a possible role of MC activation in the pathogenesis of MF-associated pruritus. The gene discussed is TAC1; the disease is mycosis fungoides.