We adopted a two step process where we selected SNPs from key genes in the Caucasian population which have met genome-wide significance and/or with replication, namely eleven SNPs in the following genes; ORMDL3/GSDMB, IL33, IL18R/IL1RL1, SMAD3, IL2RB, PDE4D, CRB1 and RAD50. These SNPs were genotyped in a UK asthma family cohort with at least two affected siblings, to test for association with clinically relevant endpoints in asthma. Here, PDE4D is linked to asthma.