Histamine, Substance P and Calcitonin Gene-Related Peptide Plasma Concentration and Pruritus in Patients Suffering from Psoriasis

Abstract

Background: Many patients with psoriasis suffer from itch. The pathogenesis of psoriatic itch still remains unknown. Objective: To evaluate the relationships between plasma levels of histamine, substance P (SP) and calcitonin gene-related peptide (CGRP) and the presence as well as intensity of itching among psoriatic patients. Patients and Methods: 59 psoriatic individuals (43 pruritic and 16 non-pruritic) and 32 healthy controls were included in the study. Itching was evaluated by a visual analog scale (VAS) and a specially designed questionnaire. Plasma concentrations of histamine, SP and CGRP were measured by RIA (radioimmunoassay) method. Results: The mean plasma concentration of histamine in psoriatic patients was not significantly different from that found in controls. No significant differences were found between plasma levels of histamine in the groups of psoriatic pruritic patients, non-pruritic psoriatics and controls. Also, there was no significant difference in SP plasma concentration between psoriatic individuals and controls or between pruritic, non-pruritic and healthy people. No relationships between the substances studied (histamine, SP) and intensity of pruritus could be revealed. The mean CGRP plasma level was markedly increased in patients suffering from psoriasis as compared to controls (p < 0.01). The mean CGRP concentration in the plasma of pruritic psoriatic patients was significantly higher than in controls (p < 0.01). This was not observed when comparing non-pruritic to healthy subjects. The mean concentration of CGRP in the plasma of pruritic patients was also higher than in that of non-pruritic ones, but this difference did not reach statistical significance. A significant correlation was found between itching intensity and CGRP plasma concentration in male subjects and in those patients who had been suffering from psoriasis for 5–20 years. There were, however, no correlations between CGRP level and itching intensity in the whole group of 43 psoriatic patients with pruritus. Conclusion: Circulatory CGRP could be an important factor in the pathogenesis of psoriatic pruritus, but this still needs further investigation.