Study of pruritus in psoriasis vulgaris : Role of tachykinins

University dissertation from Stockholm : Karolinska Institutet, Department of Medicine

Abstract: Pruritus has not been considered as the most important symptom of psoriasis. In the present thesis various methodologies have been used to investigate this symptom in psoriasis. The focus groups created a proper atmosphere for discussion on different aspects of pruritus in psoriasis. Pruritus was most common on the lower back and legs. Stress, cold weather and skin dryness were considered as the most common worsening factors for the condition. Sunbath and application of emollients with or without corticosteroids and calcipotriol cream were suggested as factors that relieved pruritus. Quality of life was affected in some patients. A comprehensive questionnaire was used to investigate in detail about pruritus in psoriasis. The frequency and intensity of pruritus were higher in women. Lower leg and scalp were reported as being the most commonly affected sites. Major aggravating factors were stress and dryness of skin. Sun, sleep and vacation could relieve to the condition. The most common anti-pruritic treatments used by the patients were topical glucocorticoids, vitamin D and emollients, while antihistamines were used by a small number of patients. Mood, concentration and sleep were negatively affected by pruritus. Substance P, neurokinins A (NKA), B (NKB) and NK-2 receptor (R), reactive nerves and substance P, NKA, NKB and their respective receptors NK-1, NK-2 NK-3 reactive inflammatory cells were more numerous in lesional than non-lesional psoriasis and healthy control skin, respectively. The pruritus intensity and number of NK-2R positive cells in lesional psoriatic skin were significantly correlated. Intradermally injected substance P induced pruritus, flare and wheal in psoriasis patients. Substance P (10-5 mol/L) induced a tendency to larger intensity of pruritus in lesional than non-lesional psoriatic skin. Histamine produced a shorter itch latency period in lesional and smaller wheal in non-lesional psoriasis skin compared to healthy individuals. In conclusion, pruritus is one of the common symptoms of psoriasis. Members of the tachykinin family might play an important role in the pathogenesis of pruritus in this disease.

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