Photobiological responses in patients with chronic actinic dermatitis and their relationship with the melanocortin-1 receptor gene Arg163Gln variant: a preliminary study

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), 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. Key words: Photosensitivity disorders; Pigmentation; Genes, Arg163Gln; Chronic actinic dermatitis; Photopatch tests