The degree of erythema in melasma lesion is associated with the severity of disease and the response to the low-fluence Q-switched 1064-nm Nd:YAG laser treatment

The most characteristic feature of melasma is the hyperpigmentation of facial area, but recent studies revealed that the melasma lesion is more erythematous than the perilesional area (1,2). In addition, it was found that the size and number of vessels are increased in melasma lesion (1,3). However, the clinical significance of erythema in melasma has not yet been understood. For the treatment of melasma, use of a low-fluence Q-switched Nd:YAG laser, socalled laser toning, has been popular, especially in Asian population (4). However, studies regarding the exact outcome, statistical significance and prevention of adverse events are lacking. We herein present the results suggesting that “erythema” in melasma may reflect the severity of disease and predict the response to the laser toning treatment. We treated 22 Korean women (aged 26–64 years, mean ± SD 42.4 ± 8.9 years) with symmetric melasma. They were treated with a collimated 1064-nm Q-switched Nd:YAG laser (Spectra VRMIII , Lutronic Corp., Seoul, Korea) using 7 mm spot size, energy fluence of 1.2 to 1.4 J/cm at 10 Hz for 5–8 passes. For eachpatient, 5–10 sessionswere performed at intervals of 1–2 weeks. The degrees of pigmentation anderythemawere assessedbymelanin index (MI) and erythema index (EI) respectively using Mexameter (Courage-Khazaka Electronic, Köln, Germany) at baseline and before every treatment. The measurements were performed on both sides of the face of each patient. In order to investigate the changes in pigmentation and erythema, we estimated the marginal means of MI and EI at each measurement applying generalized estimating equations using a single predictor, the number of treatment. They were fitted as robust estimators, with unstructured working correlation matrix and identity link function, using SPSS version 19.0 (SPSS Inc., Chicago, IL, USA). The MI significantly decreased after only one treatment compared to the baseline (p = 0.001). The trend of gradual decrease continued to the last measurement with some fluctuations, but there was no additional statistically significant decrease in MI compared to the first post-treatment MI (Figure 1). The EI also showed a significant decrease and the pattern of the change was similar with that of MI (Figure 1). There was a positive correlation between MI and EI and this relation was verified by scatter plot (Figure 2) and Spearman correlation coefficient of 0.54. In addition, we analyzed the potential factors associated with the degree of decrease in MI compared with the baseline after laser treatment. We considered five factors : age, baseline MI, baseline EI, the side of the face (left versus right), and the number of treatments. The effects of the other factors were controlled by the generalized estimating equation analysis. After controlling the others, baseline MI (p < 0.001), baseline EI (p < 0.001) and the number of treatment (p = 0.016) were associated with the degree of decrease in MI after laser treatment. When the other factors