Cystic fibrosis is a genetic condition that primarily affects the lungs and digestive system. It does, however, impact on the whole body and people with cystic fibrosis do not generally live beyond their 30s or 40s.
The condition is caused by a faulty gene and people affected produce thicker than normal mucus in their lungs and gut. This makes them prone to lung infections and they often get a blockage in the pancreatic duct, which prevents digestive juices from reaching the intestine, and which tends to cause inflammation and pancreatitis.
How common is cystic fibrosis?
Approximately one in 25 people are carriers of cystic fibrosis, meaning that they have one faulty gene. They are completely healthy. If two carriers get together and have a baby, there is a one in four chance that the child will inherit two faulty genes and be born with cystic fibrosis. Around 250 such babies are born each year, and there are over 9,000 people with cystic fibrosis in the UK.
In the last 50 years, the life expectancy of children with this genetic disease has increased significantly. In 1959, a baby born with cystic fibrosis was unlikely to live past six months. Today, it is difficult to predict a life expectancy but one study has suggested that over half of the people born in 2010 with cystic fibrosis can expect to live past the age of 38.
What causes cystic fibrosis?
The gene responsible for cystic fibrosis is called CFTR, the cystic fibrosis transmembrane regulator. Normally the CFTR gene makes a protein pump located in the cell membrane of the epithelial cells that line the lungs and intestines.
This tiny pump moves salt (sodium chloride) out of the cells and into the mucus that covers the lining. The salt attracts water, which passes out of the cells, and makes the mucus runny and less sticky. This is important, particularly in the lungs, because thinner mucus can be more easily moved by cilia – the tiny hairs that help to keep the lungs clean.
In someone with cystic fibrosis, the faulty gene makes a protein that cannot pump salt, so there is no water movement. The mucus in the gut and lungs remains thick and sticky and cannot be moved by the lung cilia. This allows bacteria to become trapped in a moist, warm environment where there is plenty of oxygen, so it is hardly surprising that someone with cystic fibrosis has frequent lung infections.
What are the symptoms of cystic fibrosis?
Symptoms usually appear in the first year of life. One in 10 babies with cystic fibrosis is born with a bowel obstruction – called a meconium ileus – that results from the meconium, the first faeces produced by the gut, being too thick to move along the bowel.
In young children, the main symptoms are:
Breathing difficulties caused by the thick mucus
A persistent cough
Frequent lung infections, often caused by bacteria that do not usually cause lung infections in people without cystic fibrosis, such as Pseudomonas aeruginosa and Burkholderia cepacia
Poor digestion. The pancreatic duct is blocked and so much of the food, including fat, goes undigested. This results in poor nutrition and a greater volume of large, oily stools.
Later in life, the cystic fibrosis can have other effects:
Slow growth as a consequence of the poor nutrition. Children are often smaller than their classmates and they may experience puberty later. Adults may find it difficult to maintain or gain weight
Diabetes. The blocked pancreatic duct can result in the degeneration of the pancreas so that it fails to make any insulin. Diabetic symptoms are different from in non-CF diabetics, but the condition is still controlled by insulin injections
Infertility. In males with cystic fibrosis the vas deferens (the sperm duct) usually fails to develop. In females the thick mucus can block the fallopian tube so that the egg cannot be fertilised.
How is cystic fibrosis diagnosed?
Screening for cystic fibrosis: routine genetic testing of newborns is done from a heel-prick blood sample that is used to check for several other congenital conditions
Genetic testing: people with a history of cystic fibrosis in the family can find out if they are a carrier by having a simple genetic test done on a sample of cheek cells. If both parents are carriers, the foetus can be tested by taking tissue from the placenta (chorionic villus sampling) or the fluid surrounding the foetus (amniocentesis)
Sweat test. Many mothers notice that their baby’s skin tastes very salty. This is because the same protein pump fails to pump salt back into the cells of the sweat gland and too much salt escapes into the sweat. The diagnosis can be confirmed with a genetic test using cheek cells.
Living with cystic fibrosis
An important part of the daily routine of anyone who has cystic fibrosis is regular physiotherapy to dislodge the mucus in the lungs. A combination of breathing exercises and manipulation are used. Parents are taught how to do this for their children. Other family members, friends or carers can be taught to do this so that no single person becomes indispensable. Adults with cystic fibrosis can learn a technique to do themselves.
Medical treatment is also essential:
Medicines for the lungs
Antibiotics to combat the lung infections. As a precaution, people who have cystic fibrosis usually take antibiotics continuously
Bronchodilator inhalers to make the airways larger
Steroid inhalers to reduce inflammation of the airways
DNase. The thick mucus traps epithelial cells that contain long DNA molecules, which make the mixture even more viscous. DNase is used to break up the DNA, making the mucus easier to dislodge.
Medication for the intestines
Pills containing digestive enzymes are taken with meals, to replace pancreatic secretions
If the patient has cystic fibrosis-related diabetes, insulin and other medications will be necessary
Other medications include treatments for osteoporosis and liver problems.
Possible future treatments for cystic fibrosis
Gene therapy treats the person with the disease by giving them working copies of the defective gene. Multiple copies of the CFTR gene could theoretically be delivered to the cells where they could be expressed, restoring normal mucus. Unfortunately, this is easier said than done. Trials have shown that delivering the genes into the lungs using viruses or spheres of lipid is possible, but the gene is not reliably expressed. This line of research may one day result in a cure for cystic fibrosis, but this is unlikely to happen in the near future.