J Dowsett and O Tully, St Vincent's University Hospital, Dublin, Ireland
© 2005 Elsevier Ltd. All rights reserved.
Cystic fibrosis (CF) is a multisystem autosomal recessive disorder caused by the mutation of a single gene on the long arm of chromosome 7 that codes for the cystic fibrosis transmembrane regulator (CFTR). This protein regulates the passage of chloride through the membrane of secretory epithelia; the dysfunction of which results in an altered composition of epithelial secretions. Clinically, CF is characterized by chronic pulmonary infection with periods of acute exacerbation, pancreatic insufficiency and excessive losses of sweat electrolytes. The latter forms the basis for the diagnostic test. The mutated gene was identified in 1989 and since then over 800 CFTR mutations have been reported, the most common of these being A F508.
Approximately 5% of the Caucasian North European and North American populations are carriers of the gene defect causing CF, leading to an approximate incidence of 1 in 2500 live births. This inheritance is illustrated in Figure 1. The incidence of CF in non-Caucasians is much lower and estimated to be around 1 in 100 000 in Oriental populations.
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