Atopic Dermatitis Mediates the Association Between an IL4RA Variant and Food Allergy in School-Aged Children

Abstract

Atopic dermatitis (AD) and food allergy (FA) may share genetic risk factors. It is unknown whether genetic factors directly cause FA or are mediated through AD, as the dual-allergen hypothesis suggests. To test the hypothesis that AD mediates the relationship between an IL-4 receptor alpha chain gene (IL4RA) variant, the human IL-4 receptor alpha chain protein-R576 polymorphism, and FA. A total of 433 children with asthma enrolled in the School Inner-City Asthma Study underwent genotyping for the IL4RA576 allele. Surveys were administered to determine FA, AD, and associated allergic responses. Mediation analysis was performed adjusting for race and ethnicity, age, sex, and household income. Multivariate models were used to determine the association between genotype and FA severity. AD was reported in 193 (45%) and FA in 80 children (19%). Each risk allele increased odds of AD 1.39-fold ([1.03-1.87], P= .03), and AD increased odds of FA 3.67-fold ([2.05- 6.57], P < .01). There was an indirect effect of genotype, mediated by AD, predicting FA; each risk allele increased the odds of FA by 1.13 (odds ratio [95% CI], Q/R= 1.13 [1.02-1.24], R/R= 1.28 [1.04-1.51]; P < .01). Each risk allele increased the odds of severe FA symptoms 2.68-fold ([1.26-5.71], P= .01). In a cohort of children with asthma, AD is part of the causal pathway between an IL4RA variant and FA. This variant is associated with increased risk of severe FA reactions. Addressing AD in children with an IL4RA polymorphism may modulate the risk of FA.