Natural history of eosinophil‑derived neurotoxin levels and the onset of allergic airway disease in preschool children.

'Atopic march' is the progression of allergic conditions through infancy and childhood. The present study investigated the association between blood eosinophil-derived neurotoxin (EDN) levels in preschool children with food allergy (FA) or atopic dermatitis (AD) and the onset of allergic airway disease [bronchial asthma (BA), allergic rhinitis (AR)]. A total of 123 children below the age of 1 year were enrolled in the present study, along with controls (n=37). Blood specimens were taken, serum EDN levels were measured and immunoglobulin E was quantified. Finally, a total of 86 subjects were analyzed. EDN values were measured at 3 time-points: before 1 year of age, before 2 years of age and before 3 years of age. The EDN levels were initially similar between those patients who did and those who did not develop allergic airway disease but then markedly diverged at the 2-year time-point (226.6 vs. 65.0 ng/ml; P<0.01) and remained divergent at the 3-year time-point (173.9 vs. 62.7 ng/ml; P<0.01). EDN levels prior to diagnosis were compared between the two groups and they were much higher in the Onset group (n=10) compared to the Non-onset group (n=67) (171.2±34.28 vs. 81.3±10.02 ng/ml; P=0.003), with 4 cases of BA and 6 cases of AR in the Onset group. After diagnosis, EDN levels were compared twice: i) At 1 and 2 years of age; and ii) 1 and 3 years of age. A significant difference was found only in the comparison at 2 years (P=0.001). In conclusion, young children with elevated EDN levels during the FA/AD disease period were more likely to develop allergic airway disease (BA, AR) in their first three years of life. A factor leading to this progression may be increased eosinophil activity.