In addition to the primary CFTR defect there are other important factors that can contribute to CF lung disease pathology including, for example, intrapulmonary proteases, mucus hypersecretion and microRNA (miRNA) expression in bronchial epithelium (Cantin et al., 1989; Voynow et al., 1998; Voynow et al., 1999; Oglesby et al., 2010), amongst others. The gene discussed is CFTR; the disease is cystic fibrosis.