CHI3L1 and asthma: A study combining GWAS with serum YKL‐40 measurement, involving 632 members of the Hutterite population of European decent (living in South Dakota) (age range 6–92 years; asthma in 11.5%, atopy in 41.2%), have shown CHI3L1 (SNP rs4950928, ‐131C‐ > G) to be a susceptibility gene for asthma, bronchial hyperresponsiveness, and reduced lung function [27 ].