A genome-wide association study of asthma indicated that the single nucleotide polymorphism (SNP) rs4950928 in the promoter region of CHI3L1 is associated with serum levels of YKL-40 in Western European and American populations [10,11], and another study illustrated that the rs4950928 G allele is significantly associated with asthma susceptibility in a population-based study of 6514 Danish adults [12]. This evidence concerns the gene CHI3L1 and asthma.