Supplementary Material for: Clinical and Spectrophotometric Evaluation of Skin Photoadaptation in Vitiligo Patients after a Short Cycle of NB-UVB Phototherapy

Background: The phenomenon of photoadaptation to narrow-band ultraviolet B (NB-UVB) radiation has been previously described in vitiligo and has usually been clinically measured by the assessment of the minimal erythema dose (MED) after phototesting. Objectives: To assess the photoadaptive response in vitiligo and healthy skin after NB-UVB phototherapy not only clinically, but also by spectrophotometry. Materials and Methods: Fourteen patients affected by generalized vitiligo underwent NB-UVB phototherapy twice weekly for 12 weeks. Before and after phototherapy, a phototesting procedure was administered on vitiligo patches and adjacent healthy skin with a solar simulated radiation (SSR). Visual assessment of the MED took place after 24 h. A spectrophotometer was used to assess the a* value and the melanin index (MI*), as signs of skin erythema and pigmentation. The photoadaptation factor (MED-PF) and the a* photoadaptation factor (a*-PF) were calculated. Results: After NB-UVB phototherapy, both vitiligo and healthy skin showed an increase in MED and MI* values and a reduction of skin erythema compared to baseline (p < 0.05). MED-PF data showed a photoadaptation in 10 (71.4%) vitiligo lesions and in 12 (85.7%) healthy skin areas. The assessment of the a*-PF showed a negative mean percentage value in all affected and unaffected skin areas. Conclusions: A short cycle of NB-UVB phototherapy can induce photoadaptation in vitiligo by increasing the MED and reducing skin erythema after stimulation with SSR. This is most likely due to the physical filter function induced by ultraviolet radiation.

研究背景：窄谱中波紫外线（NB-UVB）辐射的光适应现象此前已在白癜风患者中被报道，临床通常通过光试验后评估最小红斑量（MED）进行测量。研究目的：同时从临床与分光光度检测两个维度，评估白癜风皮损与健康皮肤在接受NB-UVB光疗后的光适应反应。材料与方法：14例泛发性白癜风患者每周接受2次NB-UVB光疗，持续12周。光疗前后，分别对白癜风皮损及邻近健康皮肤进行模拟太阳光辐射（SSR）光试验。于照射后24小时对最小红斑量进行肉眼评估。使用分光光度计检测a*值与黑色素指数（MI*），以此作为皮肤红斑与色素沉着的量化指标，并计算光适应因子（MED-PF）与a*光适应因子（a*-PF）。研究结果：NB-UVB光疗结束后，与基线水平相比，白癜风皮损与健康皮肤的MED值与MI*值均有所升高，皮肤红斑程度降低（p < 0.05）。MED-PF数据显示，71.4%（10/14）的白癜风皮损及85.7%（12/14）的健康皮肤区域出现光适应。对a*-PF的评估显示，所有受累与未受累皮肤区域的平均百分比值均为负值。研究结论：短期NB-UVB光疗周期可通过提升MED值并降低模拟太阳光辐射刺激后的皮肤红斑程度，诱导白癜风患者出现光适应，这一效应大概率由紫外线辐射诱导的物理过滤功能所介导。