Cystic Fibrosis

Cystic Fibrosis

Cystic Fibrosis is a hereditary disorder of the exocrine glands that is characterized by respiratory and digestive problems. This disorder causes the body to release extremely thick and sticky mucus that clogs the lungs and pancreas, leading to problems with breathing and digestion, infection, and ultimately death (Encarta Encyclopedia, 1993-2003, 1). Abnormal secretion of sweat and saliva glands is also characteristic of cystic fibrosis. This disease is the most common inherited disease among Caucasians, affecting 3,200 live births and affecting about 30,000 children and adults in the United States alone. Cystic fibrosis affects men and women equally, but affects white people more than black people. This disease mainly affects children and young adults and is diagnosed by the age of three. Due to the advances in genetic research, diagnosis has been made on some adults that have mild forms of the illness and even on fetuses. About 1,000 new cases of cystic fibrosis are diagnosed each year (http://www.cff.org/).

The cause of cystic fibrosis used to be a genetic mystery with affected individuals dieing in early childhood. With all of the recent advances in genetic research, the genetic basis for cystic fibrosis as been unraveled and has aided in the much earlier detection of this life threatening disease. Genetic testing can now identify more than 80 percent of people with the abnormal gene (http://health.discovery.com/).

In 1989, it was discovered that this disorder is caused by a mutation, an alteration in the structure of the gene, to a gene found on chromosome 7. The defected gene causes a change in the amino acid sequence, which is coded for by a particular gene, ultimately altering the structure of the protein that controls the normal movement of sodium chloride in and out of specialized epithelial cells. This particular protein is known as the cystic fibrosis transmembrane conductance regulator. This protein is responsible for forming a channel in the plasma membrane of cells through which chloride ions enter and leave the cells lining the lungs, pancreas, sweat glands, and small intestine (Encarta Encyclopedia, 1993-2003, 3). As a result to the malfunction or absence of the cystic fibrosis transmembrane conductance regulator, there is an impaired movement of sodium chloride ions which build up in the cells of the lungs and other organs causing water to stay inside the cells to dilute the chloride rather than being drawn out of the cells by normal chloride movement and the normal secretions of these organs (The Columbia Encyclopedia, 2000, 1). The abnormal water and chloride ion secretion results in a heavy production of a thick and sticky mucus in the lungs, pancreas, small intestine, and reproductive organs that clogs the ducts or the tubes in these organs. Clogs that form on the ducts, tubes, and passage ways of these organs will eventually form into cysts on these tubes or passage ways. In a healthy individual, the mucus is thin and slippery acting as a lubricant.

In the lungs, this thick mucus on the respiratory tracts blocks airways and impedes natural infection-fighting mechanisms found in the lungs resulting in an increase of respiratory infections. Eventually, the body's immune system will turn against its own lung tissue resulting in lung failure (Encarta Encyclopedia, 1993-2003, 3). The pancreas is referred to as both an endocrine and exocrine gland. Exocrine secretions make up a number of important digestive enzymes that are released into the intestine and aid in digestion, but the block of these pancreatic ducts, due to the thick mucus, causes these important digestive enzymes to fail and reach the small intestine resulting in an impaired break down and absorption of certain foods in the small intestine leading to severe nutritional deficiencies. This disease also causes the sweat glands to secrete excessive amounts of salt, because the sweat glands in individuals with cystic fibrosis can not reabsorb the sodium chloride ions enabling excessive amounts of salt to escape in the sweat (Encarta Encyclopedia, 1993-2003, 3). The reproductive system of both men and women exhibiting cystic fibrosis can be affected by the thick and sticky mucus. Many men with cystic fibrosis have low, or zero, sperm counts due to the clogs formed on the vas deferens, the tubules carrying sperm from the testicles to the penis, resulting in a difficulty in fathering children (http://health.discovery.com/). Women with cystic fibrosis have lower fertility and usually will have complications with birth.

Cystic fibrosis is carried as an autosomal recessive trait. This implies that in order to exhibit cystic fibrosis, both the mother and the father must carry and pass the defected gene to the child. Because of the impaired reproductive system and life threatening implications associated with this illness, it is unlikely for an individual exhibiting cystic fibrosis to reproduce and transmit this disease to offspring, meaning that the disease can only occur in a child with two carrier parents. Through carrier screening, researchers have determined that one in twenty-five Caucasians carry the gene for cystic fibrosis (Sosnowski, 2000). More than 10 million Americans are unknowing, symptom less carriers of the defective cystic fibrosis gene ultimately transmitting the disease. Each time two carriers on cystic fibrosis conceive, there is a 25 percent chance that their child will have cystic fibrosis, a 50 percent chance the child will be a carrier of the defected cystic fibrosis gene, and a 25 percent chance that the child will be a non-carrier of the gene. (http://www.cff.org/). With such a small percent resulting in non-carriers, it is no wonder cystic fibrosis is the most common inherited disease in Caucasians.

There are no known environmental factors that cause cystic fibrosis or a mutation of the gene resulting in cystic fibrosis, so it is strictly a genetic disorder. Some experts believe that an imbalance of essential fatty acids may play a role in cystic fibrosis, since some people with cystic fibrosis clearly have excessively high levels of arachidonic acid and a deficiency of another fatty acid called docosahesaenoic acid. The exact nature of the relationship between fatty acid levels and the gene defect that causes cystic fibrosis isn't clear.

Recently, more than 200 different defects in the cystic fibrosis gene have been described, many of which produce cystic fibrosis in varying degrees of severity and in varying amounts of symptoms displayed and the gland in which is involved (Encarta Encyclopedia, 1993-2003, 5). One child with cystic fibrosis may have respiratory problems but not digestive problems, while another child may have both respiratory and digestive problems (http://www.mayoclinic.com/). In some

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