Urinary eosinophil protein X and serum eosinophil cationic protein in infants and young children with atopic dermatitis: Correlation with disease activity

Background: Eosinophil cationic protein (ECP) and eosinophil protein X (EPX) or eosinophil-derived neurotoxin (EDN) are released by eosinophil granulocytes in allergic diseases. Serum ECP (s-ECP) levels have been correlated with disease activity in atopic dermatitis (AD) in adults and young patients, and high urinary EPX (u-EPX) levels in asthmatic patients seem to reflect active disease. A relationship between AD severity and u-EPX concentration in young children has not been previously studied. Objective: This study was performed to evaluate whether the severity of AD in infants and young children was correlated with s-ECP and u-EPX levels. Methods: Fifty-four infants and children (mean age, 17.7 months; range, 4-48 months) with AD and without other allergic conditions were evaluated. The severity of AD was measured by using the SCORAD index. S-ECP, serum total IgE, serum-specific IgE for common allergens, and peripheral blood eosinophil counts (PBECs) were determined. In forty-two children u-EPX was also measured. Seven age-matched control patients underwent the same determinations. Results: S-ECP and u-EPX were significantly higher in children with AD than in control children (mean, 23.9 vs 3.5 mu g/dL [P < .001] and 57.7 vs 6.0 mu g/mmol creatinine [P < .001]). A significant correlation was found between SCORAD and s-ECP (P = .002), u-EPX (P = .01), and PBECs (P = .01) and between symptom index and uEPX (P = .0004), PBECs were strongly correlated to s-ECP and u-EPX (P < .0001). However, 5 patients with moderate and severe AD (11.9%) showed low levels of s-ECP, u-EPX, and PBECs. Conclusion: S-ECP and u-EPX were useful markers of AD activity in infants and young children. When taken together, the two determinations could give more information about the clinical course of the illness. Some patients seemed to have clinical exacerbations without an involvement of eosinophils and their products.