HHIP and chronic obstructive pulmonary disease: Pillai et al. (2009) identified genetic variants in the hedgehog interacting protein (HHIP) gene that are linked with COPD; however, the relationships did not reach statistical significance at the GWAS level. Subsequently, Wilk et al. identified HHIP SNPs associated with decreased forced expiratory volume in the first second (FEV1) in a general population in the Framingham Heart Study (Hobbs and Hersh, 2014).