Investigation of eosinophilic cationic protein, eosinophil peroxidase, and eosinophil major basic protein levels in children with chronic spontaneous urticaria

Introductıon: Chronic spontaneous urticaria (CSU) is driven predominantly by mast cells; however, eosinophils are recognized as secondary effector cells. This study aimed to investigate the role of eosinophils in the pathogenesis of pediatric CSU by comparing serum levels of eosinophil granule proteins [Eosinophil Cationic Protein (ECP), Eosinophil Peroxidase (EP), and Eosinophil Major Basic Protein (EMBP)]. Methods: Children followed with a diagnosis of CSU, between August 2024 and June 2025 in our Pediatric Immunology and Allergy Department, and age- and sex-matched healthy controls were enrolled. Clinical, demographic, and laboratory data were recorded, including disease duration, triggers, and Urticaria Activity Score 7 (UAS7). Serum levels of ECP, EP and EMBP were measured from blood samples obtained from patients and healthy controls. Results: Seventy-four patients with CSU (age 2–17 years; mean 12.64±3.82; 55.4% female) and 70 healthy controls (age 2–17 years; mean 13.21±3.09; 55.7% female) were included. The primary presenting complaint was urticaria in 63.5% (n=47) and angioedema with urticaria in 36.5% (n=27) of patients. Serum ECP levels were significantly higher in the CSU group than in controls (p<0.001), whereas EP and EMBP levels did not differ significantly between groups. No significant relationships were observed between ECP/EP/EMBP levels and UAS7 scores demographic characteristics or mean eosinophil counts (p>0.05). Conclusion: This study first evaluates serum ECP, EP and EMBP levels together in pediatric patients with CSU. Our study suggests that ECP may play a role in the pathogenesis of CSU in children. These findings may also inform future development of targeted therapeutic strategies.