Cetirizine reduces the number of tryptase-positive mast cells in psoriatic patients: a double-blind controlled study.

Psoriatic plaque contains an increased number of mast cells that are thought to play an important role in the initiation and maintenance of the disease through the release of mediators such as histamine, proteoglycans, proteinases and cytokines. To verify the possible participation of these cells in the chronic inflammatory cutaneous response in psoriasis, we performed a double-blind controlled study to investigate the presence and activation of tryptase-positive mast cells in the lesional skin of 19 patients affected by active psoriasis vulgaris minima compared with five healthy, age-matched subjects. Psoriatic patients were randomized into two groups (A and B). The first group was treated with cetirizine (10 mg/three times a day for 15 days) and the second one was treated with placebo. Both groups underwent clinical staging [psoriasis area and severity index (PASI) score] and immunohistochemical evaluation [alkaline phosphatase antialkaline phosphatase (APAAP) procedure] before and after treatment. In group A, the PASI score ranged from 3.8 (SE +/- 1.00) to 1.8 (SE +/- 0.68) and in group B, from 5.0 (SE +/- 0.98) to 3.4 (SE +/- 0.47). The mean number of tryptase-positive mast cells for field, mainly distributed in the perivascular and periadnexal sites, ranged from 40.8 (SE +/- 7.15) to 21.6 (SE +/- 3.04) in group A and from 25.1 (SE +/- 3.78) to 26.3 (SE +/- 3.59) in group B (ANOVA test f = 6.95; gl = 1.16; p = 0.02). In our psoriatic patients, cetirizine significantly reduced the expression of tryptase-positive mast cells and produced a clinical improvement in erythema, suggesting a multilevel immunopharmacologic modulation of this antihistamine in psoriasis.