To investigate morphological characteristics of female melasma lesions at different clinical stages by using three skin imaging techniques.

A total of 253 female outpatients with melasma were enrolled from the Third Affiliated Hospital of Zhejiang Chinese Medicine University between June 2017 and January 2018. According to the clinical staging criteria, melasma lesions at different clinical stages were observed with reflectance confocal microscopy (RCM) , VISIA skin imaging detector and dermoscopy, and correlations of clinical staging with dendritic melanocytes, subclinical melasma and morphological changes of blood vessels were analyzed. Statistical analysis was carried out with SPSS19.0 software by using chi-square test and Mann-Whitney U test for the comparison of enumeration data.

Of 253 patients with melasma, 100 were with progressive melasma, and 153 with stable melasma. RCM showed that dendritic melanocytes were observed in 78 (78%) patients with progressive melasma, as well as in 22 (14.4%) patients with stable melasma, and there was a significant difference between the 2 groups (χ² = 102.40, P < 0.01) . VISIA skin imaging detector showed that subclinical melasma was observed in 78 (78%) patients with progressive melasma, as well as in 25 (16.3%) patients with stable melasma, and the prevalance of subclinical melasma was significantly higher in the patients with progressive melasma than in those with stable melasma (χ² = 95.26, P < 0.01) . Dermoscopy showed that the frequency of morphological changes in blood vessels did not differ between the patients with progressive melasma (74%, 74/100) and those with stable melasma (68.6%, 105/153; χ² = 0.84, P = 0.39) .

The dendritic melanocytes and subclinical manifestations under RCM and VISIA skin imaging detector can serve as reference indices for clinical staging of melasma.

Chloasma; Melanocytes; Microscopy, confocal; Dermoscopy; Clinical stages; Skin imaging detector