Abstract: 【Abstract】 Objective To detect the serum level of chitinase-3-like protein 1 （YKL-40） in patients with pemphigus vulgaris, and to analyze its correlation with the severity of pemphigus vulgaris. Methods From January 2017 to May 2018, serum samples were collected from 38 patients with pemphigus vulgaris in Department of Dermatology, the Affiliated Hospital of Southwest Medical University, and those collected from 14 age-, gender- and body mass index-matched healthy volunteers served as controls. Serum levels of YKL-40 and Th1/Th2/Th17-related cytokines were detected by using Luminex? 200TM system. Mann-Whitney U test was used to compare serum levels of cytokines between the patient group and control group; binary logistic regression was used to investigate factors independently related to the severity of pemphigus vulgaris; a receiver operating characteristic （ROC） curve was drawn, and the area under the curve, sensitivity and specificity were calculated to evaluate the ability of YKL-40 to predict the severity of pemphigus vulgaris. Results Compared with the control group, the patient group showed significantly increased serum levels of YKL-40 （expressed as median ［Q1, Q3］: 15.22 ［14.19, 15.93］ vs. 13.64 ［13.21, 14.63］ μg/L, z = -3.88, P < 0.05）, interleukin （IL）-6 （2.05 ［1.49, 4.21］ vs. 1.57 ［1.38, 1.75］ ng/L, z = -2.44, P < 0.05）, IL-7 （7.45 ［5.63，11.63］ vs. 3.77 ［2.21, 5.97］ ng/L, z = -3.26, P < 0.05］, IL-8 （6.59［3.60, 14.73］ vs. 4.36 ［2.96, 6.53］ ng/L, z = -1.96, P < 0.05）, IL-2R-α （509.08 ［386.36, 757.67］ vs. 336.44 ［309.86, 458.71］ ng/L, z = -2.35, P < 0.05）, and C5a （100.35 ［78.31, 140.84］ vs. 72.08 ［37.23, 82.08］ ng/L, z = -3.04, P < 0.05）. The concentration of serum YKL-40 gradually decreased along with the reduction of lesion areas （r = 0.634, P < 0.001）, and YKL-40 was independently correlated with the severity of pemphigus vulgaris （P = 0.025, OR = 46.54, 95% CI: 1.61, 1 347.19）. The area under the curve of YKL-40 was 0.783 （95% CI: 0.613, 0.953） for distinguishing between patients with severe to extremely severe pemphigus vulgaris and those with mild to moderate pemphigus vulgaris. Conclusion The serum level of YKL-40 is strongly correlated with the severity of pemphigus vulgaris, and has a potential value in predicting the severity of this disease.

Key words: Pemphigus, Chitinase, Severity of illness index, Biological markers, Th2 cells, Cytokines, Chitinase-3-like protein 1