The genetic polymorphism of MMP-12 gene may induce the abnormal expression of MMP12, and may also be related to the occurrence of COPD.[13] Although the results from a meta-analysis conducted in 2014 suggest that genetic polymorphisms in MMP12 gene may be strongly implicated in the development of COPD,[25] some studies since then have not supported this view.[23–24] the association between MMP12 polymorphism and COPD remains unclear. The gene discussed is MMP12; the disease is chronic obstructive pulmonary disease.