Abstract:

Li Xiuling, Yuan Chao, Yang Lijie, Jiang Wencai, Jiang Changqing Skin and Cosmetic Research Department, Shanghai Skin Disease Hospital, Shanghai 200443, China Corresponding author: Yuan Chao, Email: dermayuan@163.com 【Abstract】 Objective To explore differences in phototest and photopatch test results, and in skin color-related parameters between healthy subjects and patients with chronic actinic dermatitis （CAD）, and to examine their relationship with the melanocortin-1 receptor gene （MC1R） Arg163Gln variant. Methods Phototests were performed by using a sun simulator SUN1000, and skin color was analyzed by using Hexameter MX18 in 25 patients with CAD and 25 healthy subjects. The MC1R genotype at position -163 was determined by PCR. Photopatch tests were performed on 25 patients with CAD and 5 healthy subjects using a standard series of photoallergens （RuiMin） and an ultraviolet （UV） phototherapy equipment, SS-03A. Results Regarding phototest results, both UVA-minimal persistent pigment darkening dose （MPPD） and UVB-minimal erythema dose （MED） were significantly lower in CAD patients compared with healthy controls （both P < 0.05）, with the reduction in UVB-MED being particularly notable. Sixteen patients （64%） in the CAD group had positive photopatch reactions, including 13 （52%） cases of photoallergy. Skin color-related parameters were measured at four sites. Skin hemoglobin levels on the cheek, forehead, back of hands, inner upper arms were all significantly higher in CAD patients than in healthy controls （all P < 0.05）. However, skin melanin levels on the cheek, forehead and inner upper arms were similar between the two groups, and only those on the back of hands were significantly higher in CAD patients than in controls （P < 0.01）. Skin melanin and hemoglobin levels were significantly higher in exposed than in unexposed （inner upper arms） areas in CAD patients （all P < 0.05）. The frequency of the CGA genotype at position -163 in the MC1R gene was similar between CAD patients and controls （P > 0.05）, but that of the CAA genotype differed significantly between the two groups （P < 0.01）. UVA-MPPD and UVB-MED were both significantly lower in CAD patients with the CAA genotype at position -163 in the MC1R gene than in those without the genotype （P = 0.055, 0.325, respectively）. Conclusions Skin photobiological testing plays a critical role in the diagnosis of CAD. Further studies are needed to clarify the role of the CAA genotype at position -163 in the MC1R gene in the diagnosis, prevention and treatment of CAD.