Serum YKL‐40 Levels as a Biomarker for Disease Severity and Therapeutic Response in Atopic Dermatitis Patients

Introduction: Atopic dermatitis (AD) is a prevalent chronic inflammatory skin disease, and the related biomarkers are still under investigation. Chitinase‐3‐like protein 1 (YKL‐40) is implicated in various inflammatory conditions. This study aimed to explore changes in serum YKL‐40 levels in patients with AD and evaluate their correlation with disease severity. Methods: We enrolled 62 patients with AD (16 with mild, 24 with moderate, and 22 with severe AD) and 62 age‐ and sex‐matched healthy controls. No statistically significant difference in the clinical baseline data was observed between the two groups. Peripheral venous blood samples were collected to assess the serum levels of YKL‐40, thymus and activation‐regulated chemokine (TARC), interleukin (IL)‐4, and IL‐13. YKL‐40 levels were compared between the groups, and correlations with SCORing Atopic Dermatitis (SCORAD) scores and other serum parameters were analyzed. Patients with moderate‐to‐severe AD received either traditional treatment (cetirizine hydrochloride and compound glycyrrhizin tablets) or dupilumab for 4 weeks, with comparison of therapeutic effects and serum changes. Results: Patients with AD exhibited significantly increased serum YKL‐40 levels ( p < 0.001), which was positively correlated with SCORAD scores ( R 2 = 0.603, p < 0.001). Serum YKL‐40 levels were significantly higher in moderate‐to‐severe AD patients compared with healthy controls but not in mild AD patients ( p = 0.094). In addition, TARC, IgE, IL‐4, and IL‐13 levels were increased in patients with AD ( p < 0.001), with strong correlations to YKL‐40. Dupilumab treatment significantly reduced visual analog scale scores for itching ( p = 0.016) and YKL‐40, IL‐4, and IL‐13 levels ( p < 0.05). Conclusions: YKL‐40 levels were elevated in patients with AD and are correlated with disease severity and IL‐4, IL‐13, and TARC levels. Dupilumab effectively lowers YKL‐40 and inflammatory markers, showing therapeutic benefit.