Two Patients with Cystic Fibrosis, Nonsense Mutations in Each Cystic Fibrosis Gene, and Mild Pulmonary Disease

CYSTIC fibrosis is the most common lethal inherited disorder in the white population. It is manifested by viscous secretions in the lungs and pancreas and abnormal electrolyte composition of sweat.¹ Epithelial cells from patients with cystic fibrosis have abnormal conductance of chloride ions across apical membranes due to defective regulation of a particular chloride channel.^{2 3 4} Inadequate secretion of chloride is believed to cause the insufficient hydration of mucus in the airways and pancreatic ducts.¹ The cystic fibrosis gene has recently been identified, and it is predicted to encode a 1480-amino-acid protein termed the cystic fibrosis transmembrane conductance regulator (CFTR).^5,6 The.