The limitations of our study are its retrospective, cross-sectional design, the univariate and descriptive nature of the analyses performed, the lack of a large cohort of patients with CRS, and the not yet identified relevant mechanisms underlying including the regulation of the survival and recruitment of eosinophils through CD40-CD40L and ICOS-ICOSL pathway. This evidence concerns the gene ICOSLG and congenital rubella syndrome.