Cystic Fibrosis
Cystic fibrosis is the commonest genetic defect carried in the Western World. The incidence of carriers in the UK is 1 in 25. The faulty gene results in a defective transport system for chloride ions (sufferers lack a protein called ‘cystic fibrosis transmembrane conductance regulator’, present in normal cells). This causes the production of thick mucous which is high in sodium and chloride concentration and low in water, making it very viscous. This results in the blockage of many glands and ducts. Besides affecting the lung, it also affects the pancreas and the gut (see pancreas in the digestive tract section) and produces very salty sweat. The main effects in the lungs are of repeated episodes of chest infection, often with unusual bacteria such as pseudomonas. Treatment is aimed at preventing and treating infections, often using prolonged courses of intravenous antibiotics (which means they’re injected into veins, rather than given by mouth), and helping to drain the secretions using physiotherapy. Long-term damage involving lung fibrosis and bronchiectasis leads to progressive respiratory problems. Newer techniques involving gene therapy via inhalation may delay deterioration, but badly affected patients may come to need heart-lung transplantation.
The diagnosis may be confirmed by measuring the amount of salt produced in sweat (a sweat test). There is a screening test available to assess whether or not people are carriers of the defective gene, by taking a swab from the mouth and performing genetic analysis following amplification of the genetic material using the polymerase chain reaction.
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