TAC1 and psoriasis: For example, the pruritic-type of psoriasis is characterized by increased levels of substance P and nerve fibers; decreased levels substance P-degrading neutral endopeptidase; increased levels of NGF and/or its receptor TrkA (Nakamura et al., 2003; Chang et al., 2007; Amatya et al., 2011), decreased expression of semaphorin-3A (an axon-guidance molecule) (Taneda et al., 2011; Kou et al., 2012), and increased numbers of total and degranulated mast cells (Nakamura et al., 2003).