To identify potential mediators responsible for the CTCL-associated pruritus, we assessed serum or plasma concentrations of various known itch-associated mediators and found significantly elevated levels of IL-31, IL-33, TSLP, substance P, tryptase, and total IgE in MF patients as compared to healthy controls (Fig. 3). Here, IL31 is linked to primary cutaneous T-cell non-Hodgkin lymphoma.