Diagnosis of Cystic Fibrosis - Sarah

Classic cystic fibrosis reflects two loss-of-function mutations in the CFTR gene and is characterized by chronic bacterial infection of the airways and sinuses, fat maldigestion due to pancreatic exocrine insufficiency, infertility in males due to obstructive azoospermia, and elevated concentrations of chloride in sweat. Patients with nonclassic cystic fibrosis have at least one copy of a mutant gene that confers partial function of the CFTR protein, and such patients usually have no overt signs of maldigestion because some pancreatic exocrine function is preserved. Although a value of 60 mmol per liter or higher on the sweat chloride test is diagnostic of cystic fibrosis, the concentration of sweat chloride is usually somewhat lower in patients with the nonclassic form of the disease (approximately 60 to 90 mmol per liter) than in those with classic cystic fibrosis (approximately 90 to 110 mmol per liter); moreover, the test result is sometimes borderline (40 to 59 mmol per liter) or normal ² Some CFTR mutations that result in residual CFTR function have been linked to disease of one organ, such as late-onset pulmonary disease, congenital bilateral absence of the vas deferens, or idiopathic pancreatitis.

references
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