RÉSUMÉ
Papular urticaria [PU] is a common childhood disorder. It is a chronic allergic disease caused by insect bites. Both immediate and delayed type hypersensitivity reactions could be involved in the pathogenesis of PU. The immediate reaction is responsible for the immunoglobulin-E [IgE] response supported by T-helper 2 [Th2] cells while the delayed reaction is mediated by Thl cytokines particularly interferon-gamma [IFN-alpha]. Mast cells which are effector cells of IgE-mediated immune responses, can release vascular endothelial growth factor [VEGF] after IgE-dependant activation. VEGF was reported to play a role in the pathogenesis of many allergic conditions. This study included 28 children with papular urticaria and 15 age and sex-matched healthy controls. The age of the patients ranged from 2 to 7 years [mean, 3.5 years]. The duration of PU ranged from 3 months to 4 years. IFN-alpha, IgE and VEGF levels were quantitatively determined in serum of patients and controls by Enzyme Linked Immuno-Sorbent Assays [ELISA]. Children with papular urticaria showed significantly elevated serum levels of IFN-alpha, IgE and VEGF compared to healthy controls [p<0.05, p<0.001 and p<0.001 respectively]. A significant positive correlation was demonstrated between serum levels of IFN-y and IgE in children with papular urticaria [r-= 0.941, p<0.01]. Papular urticaria could be mediated by a complex immune response involving more than one mechanism, with evidence for both Thl response [increased production of IFN-alpha] and Th2 response [increased production of IgE] with a possible role for VEGF