Abstract
It is well recognised that genetic factors play a major role in the development of respiratory diseases such as asthma and chronic obstructive pulmonary disease. However, whilst extensive data exist on diseases caused primarily by single gene defects, such as α1-antitrypsin deficiency, the genetic factors responsible for the development of complex disease are only now being defined. Once the gene(s) responsible for the heritable element of disease risk are known, the next step is to identify the mechanisms underlying the pathophysiological effects of the causal mutations in these genes. This process can be time consuming, but allows a full understanding of the mechanisms underlying disease development to be obtained. This knowledge can then potentially be used to stratify patient groups within (or even across) disease boundaries and then to target therapy more effectively.