Abstract:

Objective The study aimed to investigate the value of reflectance confocal microscopy（RCM） in evaluating microscopic changes in moderate to severe plaque psoriasis treated with secukizumab. Methods Eleven patients with moderate to severe plaque psoriasis，three to six lesions were selected from each patient and the local psoriasis severity index（LPSI）score was used to evaluate the clinical efficacy before and after 12 weeks of treat⁃ ment；the same lesions were examined using RCM to measure changes in the area，circumference and diameter of the dermal papillae（DP）and capillary loops（CL）clearly identified at the epidermis⁃dermis junction. The groups were divided into upper limb，trunk and lower limb groups according to the site of the lesion，and the differences in DP and CL diameter change rates were compared between the groups；the correlation between DP and CL diame⁃ ter change rates and clinical efficacy was analysed using Spearman′s correlation analysis. Results A total of 53 lesions selected from 11 patients，the area，circumference and diameter of DP and CL were reduced after treatment （P<0.001）. However，12 of the 26 clinically cured（LPSI=0）lesions still had enlarged DP diameters（≥80 μm） and active cells were still visible in the lumen of some CL canals. The rate of change in DP diameter was significantly smaller in lower limb lesions than in upper limb and trunk lesions（P<0.05），with no significant difference in CL diameter change between different sites（P>0.05）. There was a strong correlation between the rate of change in LPSI and the rate of change in DP diameter before and after treatment（rs=0.644 8，P<0.000 1）and a weaker corre⁃ lation with the rate of change in CL diameter（rs=0.339 2，P=0.003 1）. Conclusion Clinical cure of lesions is not the best time to discontinue the biologics，the RCM parameters of DP and CL of psoriatic lesions can be used asmicroscopic indicators to monitor the efficacy of biologics dynamically and provide a more objective basis for biolog⁃ ics reduction and discontinuation.

Key words:

psoriasis, secukinumab, dermal papillae, capillary loops, reflectance confocal mi? croscopy