Analysis Of Sensitivity To UVA And UVB In Patients With Melasma Of Yunnan Area

Background:Melasma is a chronic discosmetic dermatosis acquired and pigmented at the exposure site,especially on female faces.According to the epidemic investigation abroad,there are about 34%of middle-aged females and 6%of middle-aged males suffering from or having ever had melasma.Melasma usually emerges,with various factors,such as sunlight exposure,hormone levels,genetic factors,among which ultraviolet(UV)irradiation is the most important driving and aggravating factor.And in the epidemiological studies,about one third of melasma cases associated with exposure to solar radiation.Yunnan is located in a high-altitude area,where melasma is common,with strong UV radiation.However,whether photosensitivity of patients with melasma are different from that of normal people,the issues whether they are related to the examination of epidermal biophysical properties of skin,and whether they are related to the severity of the disease are worth exploring.Objectives:This study aims to explore the sensitivity of patients with melasma in Yunnan to ultraviolet-A(UVA)and ultraviolet-B(UVB)by measuring minimal erythema dose(MED),and the correlation between the photosensitivity with epidermal biophysical properties of skin and the severity of melasma.Methods:116 females with melasma and 89 normal controls aged 20 to 60 from Yunnan area were included from December 2018 to July 2020.Ultraviolet-A minimal erythema dose(MED-UVA)and ultraviolet-B minimal erythema dose(MED-UVB)in patients with melasma and normal controls were detected with SUV-1000 UV solar simulator,with differences of MED-UVA and MED-UVB in melasma group and normal control group compared.Meanwhile,melasma area and severity index(MASI)score of melasma in the two groups were also evaluated by professional dermatologist.The stratum corneum hydration(SCH),transepidermal water loss(TEWL),melanin index(MI)and erythema index(EI)of patients with melasma were determined both in lesions and surrounding normal skin,and the correlation between MED-UVA and MED-UVB of patients with their epidermal biophysical properties and MASI score were analyzed.Results:1.116 patients with melasma and 89 normal controls were included in this study.The average age of patients in the melasma group was 40.62±7.23 years old,with the duration averaged 5.64±3.50 years,and MASI score averaged 8.16±5.20.And the average age of subjects in the normal control group was 38.84±7.10 years old,with no significant difference in age between the two groups(P>0.05).2.Compared to the normal control group,MED-UVA(Z=-6.190,P<0.001)and MED-UVB(Z=-2.806,P<0.05)of patients in the melasma group decreased significantly,and MED-UVA decreased more obviously.3.Through the correlation analysis of skin epidermal biophysical properties and MED in the melasma group,SCH of lesions was significantly positively correlated with MED-UVA(rs=0.420,P<0.001)and MED-UVB(rs=0.273,P=0.005).MI of lesions was negatively correlated with MED-UVA(rs=-0.189,P=0.043)and MED-UVB(rs=-0.202,P=0.040).According to the analysis of surrounding normal skin,only SCH showed a significant positive correlation with MED-UVA(rs=0.246,P=0.012).4.In the melasma group,MASI score had a significant negative correlation with MED-UVA(rs=-0.740,P<0.001)and MED-UVB(rs=-0.475,P<0.001),suggesting that the lower the MED value of patients with melasma,the higher the MASI score.Conclusions:1.Patients with melasma had higher sensitivity to UVA and UVB,and the photosensitivity to UVA was more significant.2.The lower the MED value,the lower the corneum hydration of cuticle in lesions, and the higher the melanin index.3.The lower the MED value of patients with melasma,the higher the MASI score.This suggest that the higher photosensitivity,the more serious the skin lesions.