Polymorphisms in IL13, total IgE, eosinophilia, and asthma exacerbations in childhood

Background: It is unclear whether single nucleotide polymorphisms (SNPs) in the gene for IL-13 (IL13) influence asthma severity and/or asthma morbidity. Objectives: To examine the relation between IL13 SNPs and asthma-related phenotypes in 2 independent populations. Methods: We used family-based methods to test for association between SNPs in IL13 and asthma-related phenotypes in Costa Rican children with asthma. We attempted to reproduce significant findings in white (non-Hispanic) children with asthma in the Childhood Asthma Management Program (CAMP). Results: In Costa Rica and in CAMP, the A allele (Gin) of IL13 coding SNP (rs20541) was significantly associated with increased eosinophil count (P <.011 in both studies) and increased serum total IgE (P <.054 in both studies). The T allele of IL13 promoter SNP (rs1800925) was inversely associated with asthma exacerbations in Costa Rica (P =.069). Although this SNP (rs1800925) was not associated with asthma exacerbations among all white children in CAMP, it was associated with increased risk of asthma exacerbations among children on inhaled corticosteroids (P :=.02). Conclusion: Polymorphisms in IL13 were significantly associated with serum total IgE and eosinophil count in 2 populations. IL13 polymorphisms may also be associated with asthma exacerbations, and this effect may be dependent on medication use. Our study is the first to report a potential negative interaction between a genetic polymorphism and response to inhaled corticosteroids. Clinical implications: Polymorphisms in IL13 are associated with serum total IgE and eosinophil count and may be associated with asthma exacerbations.