ABSTRACT
I. Introduction The discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene led to a significant increase in our knowledge and understanding of the spectrum of disorders associated with functional alterations in the CFTR gene. Prior to this discovery, cystic fibrosis (CF) was thought to be a multisystem disease that manifests clinically either at birth (with intestinal obstruction) or in infancy/early childhood (with failure to thrive and recurrent pulmonary symptoms) (1). Great advances in molecular analysis techniques have led to not only the identification of more than 1550 CFTR mutations (2) but also the recognition of a wide spectrum of diseases associated with mutations in the CFTR gene. What was once considered a disease of infants and young childhood is no longer the case as individuals with symptoms manifesting in adolescence and adulthood are receiving a diagnosis of CF. This has been complicated by the fact that several diseases that resemble CF at an organ-specific level have also been found to be strongly associated with mutations in the CFTR gene. Consequently, the clinical diagnosis of CF disease is not always straightforward because progress in molecular genetics has not been matched by equal progress in our understanding of the clinical consequences of the majority of known CFTR mutations.
