IREB2 and chronic obstructive pulmonary disease: Several GWASs have identified a genetic loci of susceptibility, including FAM13A, CHRNA5/3, IREB2, MMP3/MMP12, TGFB2, and HHIP. The HHIP gene has been related to the FEV1/FVC ratio, FEV1, or both parameters of lung function, which are essential for diagnosis and COPD classification according to GOLD guidelines.