CHI3L1 and asthma: These findings indicate that the CHI3L1 (−131 CC, rs4950928) genotype and serum YKL-40 are not further implicated in the pathogenesis of asthma, but YKL-40 may be a potential biomarker of inflammation related to the severity of asthma—the more severe the asthma, the higher the serum YKL-40.