Cystic fibrosis (CF) is acommon lethal autosomal recessive childhood genetic disorder which is popularin the Caucasian population with a carrier occurrence of one in 25 (Davidson and Porteous, 1998).It has been reported that onein 2500 child births are affected and have an average life expectation of 28years. It is an inherited disease, heterozygotes carry one normal CF allele andone mutant allele who are asymptomatic and chosen carriers. However, the childwho has two carriers has a one in four chances of inheriting a mutation fromeach parent and may be affected with CF (Collins, 1992).The cause of CF is bymutations in the CFTR (cystic fibrosis transmembrane conductance regulator)gene.
There are more than 1900 known mutations in the CFTR gene which causes CFand disrupts the work of chloride channels. CFTR is a protein which can befound in various different cell types including; liver, pancreas, sweat ducts,reproductive tract, epithelium and submucosal glands. The CFTR protein inhabitsin the surface where epithelial cell lines with the digestive system, lungs andsweat glands. The production of thick, sticky mucus in specific organs such theairway of the lungs is due to the release of chloride. Thicker fluids arecreated when chloride ions are incapable to exit the cell well through the CFTRprotein, due to cells absorbing water due to osmosis.
Sodium chloride (salt) is present in thehumans sweat. Mostly mutations that cause CF substitute at least one DNA base,which leads to the building material of DNA for another or delete a smallnumber of DNA bases. The most common gene is the deletionof phenylalanine at codon 508 (can be also known as ?F508).Approximately 70% of patients with cystic fibrosis have this deletion of codon (Whittaker, 2007).There are also other mutations such as; G542X (part of mutation class 1), G551D(part of mutation class 3), R117H (part of mutation class 5) and many more.Malabsorption of essential nutrients is alsoanother problem which can be found in CF patients, these leads to poor weightgain, growth obstruction, delayed puberty and muscle wasting.
Whereas there arepeople with Bronchiectasis which is the termination result of chronicinflammation and mucus blockage in the CF lung.The signs and symptoms that can be found inchildren with a median age are; gastrointestinal (GI) symptoms which include –meconium ileus, abdominal distention, intestinal obstruction. The respiratorysymptoms include – coughing, recurring wheezing, continual pneumonia, unusualasthma and chest pain. There may also be physical signs such as; rhinitis andnasal polyps (nose), wheeze or cackles, cough, abdominal distention, dry skin andrectal prolapse (GI tract).
The diagnosis found for CF are the sweat chloridetest, trypsinogen blood test, some may need lung transplant, airway clearancetechniques, antibiotics for chronic infections and many other treatments. Due tothe existence of the 1900 known mutations and various other unknowns it isdifficult to find an actual cure or define an effective treatment for thedisease.