Alarmin Levels and Gastroesophageal Reflux Disease in Children: Significant Elevation of Thymic Stromal Lymphopoietin

<b>Background/Objectives</b>: In children, gastroesophageal reflux disease (GERD) may lead to epithelial barrier dysfunction and the release of thymic stromal lymphopoietin (TSLP), interleukin-25 (IL-25), interleukin-33 (IL-33) and periostin, known as alarmins. These cytokines are associated with type 2 inflammation and may contribute to respiratory and allergic conditions. The main purpose of this study is to evaluate serum concentrations of TSLP, IL-25, IL-33, and periostin in children with and without GERD and to assess their relationships with bronchial hyperresponsiveness (BHR) and sensitization to inhaled allergens. <b>Methods</b>: The study included 93 children aged 7-17 years. GERD was diagnosed based on 24-h esophageal pH impedance monitoring. Serum levels of TSLP, IL-25, IL-33, and periostin were measured using enzyme-linked immunosorbent assay (ELISA). It should be noted that the assay used does not distinguish between TSLP isoforms, which represents a limitation of the study. BHR was assessed via a methacholine challenge test, and allergen sensitization was determined using skin prick tests and allergen-specific immunoglobulin E (asIgE). <b>Results</b>: Serum TSLP levels were significantly higher in children with GERD compared to those without, whereas IL-25, IL-33 and periostin did not differ notably between groups. Periostin was associated with the degree of sensitization to inhalant allergens, but no significant links were found between cytokine levels and bronchial hyperresponsiveness. <b>Conclusions</b>: Significantly higher TSLP levels were noted in children with GERD than in those without. Hence, TSLP may have a potential role as a biomarker of epithelial immune activation in pediatric GERD. In addition, periostin was associated with sensitization to inhalant allergens, although it did not differentiate between children with and without GERD.