Pruritus：Mechanism and Treatment

• Main Authors: Mei-Ju Ko, 柯玫如
• Other Authors: 紀秀華
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/07719649407913297419

博士 === 國立臺灣大學 === 臨床醫學研究所 === 102 === Pruritus is the dominant symptom of skin disease and a frequent manifestation of systemic disease. It causes serious discomfort, anxiety, depression, sleeping disorders, considerable skin damagend and has substantial effects on quality of life. We conducted a cross-sectional study to investigate the association of glycemic control with generalized pruritus in type 2 diabetes. A total of 385 patients with type 2 diabetes who attended the diabetes care system underwent cutaneous examination by a dermatologist. A detailed interview questionnaire including visual analogue scale was used to assess various characteristics and the intensity of pruritus. Generalized pruritus was noted in 27.5% of the diabetic patients. As a result of pruritus, 24.5% of the patients had difficulties in falling asleep, 15.1% had disturbance of sleep, and 9.5% needed soporifics. Patients who had a higher postprandial glucose level had a higher probability of having generalized pruritus [OR=1.41 (95% C.I.: 1.05–1.90), P=0.02] in type 2 diabetic patients. We found generalized pruritus in patients with type 2 diabetes mellitus is associated with PC glucose control. This finding arouses the physicians to pay more attention to pruritus in diabetic patients and to motivate the patient for better blood glucose control. Uremic pruritus is also one of the most common and bothersome symptoms in patients with chronic kidney disease, with approximately 40-90% of patients on long-term maintenance dialysis suffering from this problem. To date, the mechanisms of uremic pruritus remain poorly characterized. We conducted a prospective cohort study of patients with maintenance hemodialysis in the hemodialysis center. Patient demographic and clinical characteristics, laboratory parameters, dialysis adequacy (assessed by Kt/V), and pruritus intensity were recorded at baseline and follow-up. Change score analysis of the difference score of VAS between baseline and follow-up was performed using multiple linear regression models. A total of 111 patients completed the study. Linear regression analysis showed that lower Kt/V and use of low-flux dialyzer were significantly associated with the aggravation of pruritus after adjusting for the baseline pruritus intensity and a variety of confounding factors. The optimal threshold value of Kt/V for pruritus was 1.5 suggested by both generalized additive models and receiver operating characteristic analysis. The cut-off value of 1.5 for Kt/V suggested by our study for pruritus is slightly above the target levels reducing mortality recommended in clinical practice guidelines, which not only implies that a Kt/V higher than the current standard may not further improve survival but may improve the quality of life, but also indicates that the clearance of pruritogenic substances could influence the intensity of pruritus. The therapeutic options for uremic pruritus are limited and unsatisfactory. Broad band ultraviolet B phototherapy has been demonstrated to be effective in the treatment of uremic pruritus in previous studies. Recently there is a trend of replacing BB-UVB phototherapy units with narrowband ultraviolet B (NB-UVB) units, as studies have demonstrated that NB-UVB is more efficacious in the treatment of psoriasis. However, studies regarding NB-UVB phototherpy for uremic pruritus are rare. A single blinded, randomized control trial was conducted to investigate the efficacy of NB-UVB phototherapy in uremic pruritus. Eligible participants were adults older than 18 years old, with CKD stage 3 to 5 and 5D. Patients with pruritus of visual analogue scale score over 5, itching duration of more than 2 months, and refractory to oral antihistamines and topical emollients were enrolled. The treatment group received NB-UVB phototherapy 3 times per week for 6 weeks. The dose of NB-UVB started from 210 mJ/cm2 and was increased by 10% at each time. The control group received time-matched exposures to long-wave ultraviolet light (UVA).Visual analogue scale score was evaluated weekly for pruritus intensity for 12 weeks. The characteristics of pruritus were also assessed by a questionnaire at baseline and after 6-week phototherapy. Both NB-UVB and control groups have significant and comparable improvement in the pruritus intensity VAS scores during the period of phototherapy and follow-up. Compared to control group, the NB-UVB group showed a significant improvement in the involved body surface area affected by pruritus (p = 0.006), but not in sleep quality. More detailed regression and estimating analysis revealed that the patients in the NB-UVB group had lower pruritus intensity at week 6, week 10, and week 12. This may indicate a beneficial difference at certain time points, but the effect seems marginal. NB-UVB phototherapy does not show a significant effect in reducing pruritus intensity compared to control group for refractory uremic pruritus. This finding may imply that although NB-UVB has been demonstrated to be more effective than BB-UVB for the treatment of psoriasis, its superior effect should not be directly extrapolated to other potential phototherapy-responsive dermatoses, such as uremic pruritus in this study.