الفهرس 
Introduction and aim of the workOnly 14 pages are availabe for public view
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Abstract
Cystic fibrosis (CF) is the most common autosomal recessive disease among the Caucasian people. It is life threatening disorder that causes severe lung damage and nutritional deficiencies. It is the most common cause of chronic exocrine pancreatic insufficiency. It is responsible for many cases of salt depletion, nasal polyposis, pansinusitis, rectal prolapse, pancreatitis, cholelithiasis and insulin-dependent hyperglycemia. CF may be presented as a failure to thrive and occasionally as cirrhosis or other forms of hepatic dysfunction. It usually develops during childhood and early life, so enters into the differential diagnosis of many pediatric conditions. CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene which produces the CFTR protein. This protein has been shown to function as a Cl- channel. CFTR is expressed in the epithelial cells in the lungs, pancreas, colon, sweat glands, liver, and salivary glands. It is required to regulate the components of sweat, digestive juices, and mucus. Defective CFTR function makes the membranes of epithelial cells unable to secrete chloride ions with excessive sodium absorption through these membranes. Consequently, there is decreased water excretion with the resultant production of thick tenacious dehydrated secretions. Thick mucus favours infection, airway injury and lung damage. Tenacious secretions also result in defective exocrine pancreatic function The incidence of CF varies from one ethnic group to another and even within different regions of the same country. Generally, the CF gene is most prevalent among Caucasians in Northern America, North and Central Europe in individuals who come from these areas. It is much less common, although not rare, among Afro-Americans. CF is not uncommon among Arabs and people of the Indian subcontinent, but it is very rare in the Chinese and Japanese Molecular analysis of the CFTR gene has led to the identification of more than 1000 different mutations but most of them are rare. The most prevalent mutation is the (∆F508) which results from deletion of a single phenylalanine residue of the protein’s 508 position, and shortens CFTR by one amino acid. It is considered as a severe form of mutation because it produces an early onset of chronic pneumopathy, pancreatic insufficiency, and limited life-span in homozygotes. The sweat electrolyte testing remains the standard approach to diagnose CF with elevated sweat chloride and sodium, and a sweat Cl- /Na+ ratio above 1. Measuring stool fat and pancreatic proteolytic enzymes can serve as a documentation of a defective exocrine pancreatic function. Genetic testing for the prevalent CFTR mutation(s) is a sure diagnostic test of CF especially in cases of equivocal sweat tests. Neonatal screening by serum immunoreactive trypsin and genetic testing is a rising issue. Prenatal diagnosis is possible when the common mutations are known in a community. Recent advances in diagnostics, nutrition, and respiratoiy therapy have dramatically influenced the lifespan of CF patients. The long-term outcome, however, remains dismal. Lung transplantation and liver transplantation are resorted to in cases of end-stage organ failure. Trials of gene therapy in cystic fibrosis are steadily going on.