RESUMEN
Alopecia areata [AA] is a dermatosis involving the sudden occurrence of bald patches on the scalp. Although its aetiology is not entirely clear, much clinical evidence suggests that components of the nervous system such as psychological and neurogenic factors can influence the course of AA. The aim of this work was to study the role of substance P [SP] and its degrading enzymes in AA by immunohistochemical staining for expression of SP, neutral endopeptidase [NEP] and angiotensin - converting enzyme [ACE]. The results showed that the center of the areas of hair loss of patients with AA were richly innervated by SP-staining nerve fibers. Strong expression of NEP, was observed in hair follicles. Expression of NEP in hair follicles from the margins of areas of hair loss was stronger than in normal controls, but was weaker than in the center of the areas of hair loss. In addition, endothelial immunoreactivity for angiotensin-converting enzyme was not observed in the center of the areas of hair loss, which was insignificant contrast to normal controls as well as to the margins of areas of hair loss where it was expressed. In conclusions, these findings suggest that SP is endogenously released by dermal nerve fibers around hair follicles and this seems to be important in the regulation of endothelial-leucocyte interactions in AA. NEP is augmented in follicular structures and ACE is diminished in perifollicular vessels in AA lesions. Such characteristics suggest that S P and its degrading enzymes involved in the pathogenesis of AA