[Role of genetic factors in the development of COPD]

As only a small portion of smokers develop clinically-apparent COPD, there should be some factors relevant to the susceptibility to smoking. Several studies have demonstrated an increased risk of COPD within families of COPD probands. Recent exploratory studies have revealed a number of candidate genes that may influence a person's risk of COPD, including MMP-9, microsomal epoxide hydrolase, glutathione S-transferase, hemeoxygenase, and TNF-alpha. However, the results from other laboratory are often inconsistent, and there have been no genes except alpha 1-antitrypsin, which have been definitely confirmed to explain the susceptibility to smoking in the development of COPD. It is of note that the susceptibility to smoking could be explained also by non-genetic factors such as adenovirus latent infection to the airways.