Recent genome-wide association studies (GWAS) have identified four susceptibility loci associated with COPD including 4q22 (FAM13A), 4q31 (HHIP), 15q25 (CHRNA3/CHRNA5/IREB2) and 19q13 (RAB4B, EGLN2, MIA, CYP2A6) [9]–[11]. Here, RAB4B is linked to chronic obstructive pulmonary disease.