Cystic fibrosis, «SIHS tihk fy BROH sihs», is a hereditary disease in which certain glands in the body secrete large amounts of abnormally thick mucus. Accumulation of mucus can block the ducts of these glands and eventually may block the passageways of organs into which the ducts empty. This accumulation of mucus may damage many organs, particularly the lungs, pancreas, and liver. Cystic fibrosis, often abbreviated CF, is also called mucoviscidosis.
The first symptoms of cystic fibrosis usually occur during infancy or early childhood. Infant deaths from CF are often caused by a blockage in the intestines. Patients who survive early infancy develop breathing difficulties because the thick mucus blocks their air passages. Many patients also suffer from frequent lung infections. Lung problems are the most common cause of death of CF patients. Cystic fibrosis patients may fail to digest their food completely because plugs of mucus may prevent the pancreas from secreting digestive enzymes. Physicians can diagnose CF by testing the patient's perspiration. People with the disease have much sodium chloride (salt) in their perspiration.
In 1989, researchers identified a gene called cystic fibrosis transmembrane conductance regulator (CFTR), which is responsible for CF. This gene, on a pair of chromosomes designated chromosome 7, normally allows chloride to pass through the cells that line many organs. A person who inherits a pair of abnormal CFTR genes cannot effectively absorb chloride into his or her cells and has CF. But scientists do not fully understand how the impaired chloride movement in cells causes the abnormal secretion of mucus found in CF patients.
People who carry one normal and one abnormal CFTR gene do not have the disease themselves. They are called carriers. Couples who plan to have children can be tested to see if they are carriers of the abnormal gene. A child of two carriers has a 1 in 4 chance of inheriting cystic fibrosis.
Cystic fibrosis cannot yet be cured. Doctors use antibiotics to fight the lung infections. Digestion can be improved by special diets and by pills that contain the missing enzymes. A drug called DNase is used for treatment of CF. The drug is genetically engineered from an enzyme that occurs naturally in the human body. DNase breaks down the substances that thicken mucus in the airways. Gentle pounding on the chest helps loosen the mucus from clogged airways so that the patient can cough it up.
In addition, scientists continue to try to develop techniques using gene therapy for patients with cystic fibrosis. Gene therapy involves replacing the abnormal genes with copies of normal genes.
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