Density of mast cells and intensity of pruritus in psoriasis vulgaris: a cross sectional study.

BACKGROUND: Psoriasis is a chronic and prevalent disease, and the associated pruritus is a common, difficult-to-control symptom. The mediators involved in psoriatic pruritus have not been fully established.

OBJECTIVE: To evaluate associations between the number of mast cells in psoriatic lesions and the intensity of pruritus.

METHODS: 29 patients with plaque psoriasis were recruited. In all participants, Psoriasis Area and Severity Index and Body Surface Area were assessed. A questionnaire was administered to obtain clinical information and the Dermatology Life Quality Index. Pruritus was assessed using a visual analog scale and skin biopsies were performed for staining with Giemsa and Immunohistochemistry with C-Kit.

RESULTS: Pruritus was observed in 91.3% of our patients. Median VAS was 6 (p25-75: 2-8). The immunohistochemical method revealed a mean of 11.32 mast cells/field and Giemsa staining revealed a mean of 6.72 mast cells/field. There was no correlation between the intensity of pruritus and mast cell count, neither in Immunohistochemistry (p = 0.15; rho = -0.27) nor in Giemsa (p = 0.16; rho = -0.27). Pruritus did not impact on the Dermatology Life Quality Index (p = 0.51; rho = -0.13).

STUDY LIMITATIONS: The small sample size may be considered the main limitation of our study.

CONCLUSIONS: Although mast cells are mediators of pruritus in many cutaneous diseases, our findings support that psoriatic pruritus is a complex disorder with multifactorial, complex pathophysiology, involving pruritogenic mediators others than mast cells.