Neuropeptides and their receptors in psoriatic skin in relation to pruritus

BACKGROUND: Pruritus in patients with psoriasis has been reported to be more common than previously thought. OBJECTIVES: To determine the actual prevalence of pruritus in psoriasis according to severity of psoriasis and to verify the hypothesis of involvement of neuropeptides and their receptors in psoriatic pruritus. METHODS: We analysed questionnaire replies from 152 patients with chronic plaque-type psoriasis and we assayed the expression of neuropeptides and their receptors in lesional skin biopsies obtained from psoriatic patients with pruritus compared with those from psoriatic patients without pruritus, nonlesional skin of patients with pruritic psoriasis and normal controls by confocal laser scanning microscopy. RESULTS: Of the 152 patients with psoriasis, 112 (73.7%) had pruritus, and these patients had a higher mean Psoriasis Area and Severity Index (PASI) score than psoriatic patients without pruritus. There was positive correlation between the PASI score and the intensity of pruritus. Keratinocytes in the psoriatic plaques of patients with pruritus showed consistently increased expression of substance P receptor (SPR), high-affinity nerve growth factor receptor (TrkA) and calcitonin gene-related peptide receptor (CGRPR). CONCLUSIONS: Pruritus is a common feature in psoriasis. Considering the well-known roles of neuropeptides in pathogenesis of both psoriasis and pruritus, increased SPR, TrkA and CGRPR may be involved in the pathogenesis of pruritus in psoriasis and in the severity of psoriasis.