In addition to these SNPs in PTGDR, the promoter polymorphism −731A>G and the intronic variant 6651C>T were found to be associated with asthma, atopic asthma, and bronchial hyperreactivity in families from UK, with similar results for 6651C>T in a Danish study (Zhu et al., 2007). Here, PTGDR is linked to asthma.