Interestingly, the GWAS study for ACO and COPD failed to identify known asthma-associated genetic loci such as ORMDL3, IL1RL1 and IL4R [135], indicating that ACO was not just an overlapping condition of asthma and COPD but was associated with a specific genetic background independent of asthma or COPD. Here, ORMDL3 is linked to asthma.