Woodruff et al31 demonstrated that TH2-high and TH2-low asthma phenotypes, currently often referred to as type 2–high and type 2–low asthma phenotypes, can be differentiated on the basis of the expression levels of IL-13– and IL-13–inducible genes, including POSTN, which encodes periostin. Here, POSTN is linked to asthma.