A Preliminary Study On The Characteristics And Mechanism Of Pruritus In Psoriasis

[Background and Objective]Pruritus is defined as an unpleasant sensation that provokes a desire to scratch. It isthe most common clinical symptoms of psoriasis. Because itching is not life-threatening,so its impact is often underestimated. But pruritus can affect the emotional and mentalstate of the patient seriously. Repeated scratching will cause the release of inflammatorymediators and more intense itching. Thus it will form the vicious cycle of itching andscratching, and it will have a great negative impact on quality of life in patients withpsoriasis. The clinical treatment of psoriatic pruritus is difficult, and for the treatment,there is no effective drug and means. Histamine can cause itching, but the effect ofantihistamines in psoriatic pruritus is not obvious. Histamine seems not to participate inthe mechanism of pruritus in psoriasis. The mechanisms of psoriatic pruritus arecomplex, and it has not been elucidated yet.This study focused on the investigation and analysis of the characteristics of pruritusand quality of life in patients with psoriasis. We also explored the impact on the qualityof life in patients with psoriasis that caused by itching. At the same time, we made apreliminary study on the roles of Histamine receptor, Leukotriene B4receptor andInterleukin-2in pruritus of psoriasis vulgaris by immunohistochemistry. It will providenew ideas for further research of the mechanisms and clinical treatment of psoriaticpruritus[Methods and Results]Part one: A study on pruritic characteristics and quality of life in patients with psoriasisA questionnaire of pruritus and quality of life in patients with psoriasis was developed with the combination of the already existing international scale and clinicalpractice. We investigated and analyzed the pruritic characteristics and its related factors.At the same time, we evaluated the quality of life in patients with psoriasis. Accordingto the clinical investigation, we found that there were89.31%patients with differentdegrees of itch in131patients with psoriasis.Of these pruritic patients, the mood of87.18%patients and the sleep of62.39%patients were affected because of pruritus.Correlation analysis showed that the maximum itch intensity, itch frequency, itchduration and psoriasis severity were positively correlated with erythema, infiltration,desquamation of lesions (P<0.05). Our study also showed that the impact on mood sleepand quality of life were positively correlated with itch intensity, itch frequency and itchduration(P<0.05).Part two: A preliminary study on the mechanism of pruritus in patients with psoriasisvulgarisWe detected the expression levels of Histamine receptor, Leukotriene B4receptor andInterleukin-2in epidermis of psoriasis vulgaris by immunohistochemical technique, andexplored their relationship with the mechanisms of psoriatic pruritus. It was found thatH1R，H2R，BLT1，BLT2and IL-2were all expressed in lesional tissue and non-lesionaltissue of pruritic patients with psoriasis. In addition, they were also expressed in normalskin tissue. We also found that the expression intensity of H1R,H2R,BLT1,BLT2andIL-2in lesional tissue was significant higher than non-lesional tissue and normal skintissue（P<0.05）.But there was no difference between non-lesional tissue and normalskin tissue（P>0.05）. Correlation analysis showed that the expression intensity of H1R，H2R，BLT1，BLT2and IL-2in lesions of psoriasis were not correlated with themaximum itch intensity, itch frequency, itch duration（P>0.05）.But the expression ofBLT1and BLT2in lesions of psoriasis was positively correlated（P<0.05）. [Conclusions]1.pruritus was correlated with psoriasis severity,and it had a great negative impacton mood, sleep and quality of life in patients with psoriasis.2.The expression of H1R，H2R，BLT1，BLT2and IL-2were upregulated in lesions ofpruritic patients with psoriasis. It suggested that they may be involved in thepathogenesis of psoriatic pruritus. However, because of the limitations of the sampleand the experimental method, we cound not found the relationship between theexpression intensity and pruritus severity. Thus, their roles in the mechanisms ofpsoriatic pruritus need further study.