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 granulo cytes in allergic diseases. Serum ECP (s-ECP) levels have been correlated w ith 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, 4-4 8 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 eosinoph il counts (PBECs) were determined. In forty-two children u-EPX was also mea sured. 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 betwe en SCORAD and s-ECP (P = .002), u-EPX (P = .01), and PBECs (P = .01) and be tween 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 a nd young children. When taken together, the two determinations could give m ore information about the clinical course of the illness. Some patients see med to have clinical exacerbations without an involvement of eosinophils an d their products.