WOS: 000476503500003PubMed ID: 29922975Purpose The aim of the study was to evaluate whether YKL-40 (chitinase 3-like 1 protein) plays a role in pterygium pathogenesis. Methods We included 42 primary pterygium patients and 24 control subjects with normal bulbar conjunctiva in the study. The pterygium patients were classified into the atrophic, fleshy, and intermediate groups according to the Tan classification. We then surgically removed the primary nasal pterygium and normal bulbar conjunctiva from the patients and immunohistochemically investigated YKL-40 expression. Results YKL-40 expression was statistically significantly higher in the epithelial, endothelial, and stromal cells of the pterygium tissues than in the control tissues (P=0.009, P=0.003, P=0.002, respectively). There was no significant correlation between the pterygium subgroups and YKL-40 expression (P > 0.05). Conclusions We believe YKL-40 may play a significant role in pterygium pathogenesis.Ahi Evran University Scientific Research Projects Coordination UnitAhi Evran University [TIP.A4.17.002]This work was supported by the Ahi Evran University Scientific Research Projects Coordination Unit. Project Number: TIP.A4.17.002