Heterogeneity of interleukin 5 genetic background in atopic dermatitis patients: significant difference between those with blood eosinophilia and normal eosinophil levels

Background: Blood eosinophil levels in patients with atopic dermatitis vary widely during exacerbation of the disease. We considered that in addition to environmental factors, the genetic background involved with elevating blood eosinophil levels might be heterogeneous among atopic dermatitis patients. Objective: We attempted to determine whether a polymorphism of the interleukin (IL)5 gene plays a role in atopic dermatitis, particularly in those patients with blood eosinophilia. Due to the close relation of blood eosinophilia to high IgE productivity, we also assessed these polymorphisms in patients with high IgE concentrations. Methods: We determined the genotype of the IL5 polymorphism - 703C/T in 451 atopic dermatitis patients and 116 normal subjects. The patients were classified into three groups by blood eosinophil levels; less than 7%, from 7 to 15%, and more than 15%, as well as by serum IgE concentrations; less than 500 IU/ml, from 500 to 2000 IU/ml, and more than 2000 IU/ml. Results: IL5 - 703C/T was not significantly associated with either total atopic dermatitis patients or individual patients who had both blood eosinophilia and high IgE productivity. However, the distribution of the IL5 - 703C/T genotype was significantly different between patients with either blood eosinophilia or high IgE productivity and those without either condition (P = 0.0476, P = 0.0088, respectively). Conclusion: These results suggest that the IL5 gene may play a role in blood eosinophilia associated with atopic dermatitis. We also considered that the IL5 - 703C/T gene polymorphism does not have a direct relationship to disease specificity. (C) 2003 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.