A population-based cross-sectional study demonstrated that in serum of COPD, MMP-9 concentration is higher compare to non-COPD, and production of cough and decreasing FEV1 were associated with MMP-9 in COPD (Legrand et al., 1999; Linder et al., 2015). The gene discussed is MMP9; the disease is chronic obstructive pulmonary disease.