TAC1 and alopecia areata: For another example, Toyoda et al. reported that the expression of substance P (SP), a potent proinflammatory neuropeptide, was enhanced in a patient with alopecia areata (AA), a dermatosis involving the sudden occurrence of bald patches on the scalp, and that NEP (which can degrade SP) is also up-regulated in AA follicles [24].