Cystic fibrosis is an autosomal recessive genetic condition, which means that people are born with it. The genetic condition occurs equally in males and females.
To have a child with cystic fibrosis, both parents must be a carrier of the cystic fibrosis gene change . If both parents are carriers of the cystic fibrosis gene change, then with each pregnancy there is:
- a 25% chance of that child having cystic fibrosis;
- a 50% chance that child will not have cystic fibrosis, but will be a carrier of the cystic fibrosis gene; and
- a 25% chance of that child neither having cystic fibrosis nor being a carrier.
In Australia 1 in 2,500 babies are born with cystic fibrosis every year, about one every four days.
Around 1 in 25 Australians carry the cystic fibrosis gene – that’s one million people – and most are unaware that they are carriers. Because carriers of cystic fibrosis are unaffected and show no symptoms, it is hard for them to appreciate that cystic fibrosis may be a real risk.
Any one of us could be a carrier and not know it. There are about one million unaware carriers in Australia.
In Tasmania, 1 in 20 people carry the cystic fibrosis gene. This is the second highest rate in the world behind Ireland.
How cystic fibrosis affects the body
While people with cystic fibrosis may look outwardly healthy, they are living with a life-limiting condition that affects their body in many ways. Cystic fibrosis is a complex condition, however, and people with cystic fibrosis may experience a difference in the severity of symptoms compared to others.
Cystic fibrosis primarily affects the lungs and digestive systems due to an exocrine malfunction that is responsible for producing saliva, sweat, tears and mucus. There is currently no cure.
People with cystic fibrosis develop an abnormal amount of excessively thick and sticky mucus within the lungs, airways and the digestive system. This causes impairment of the digestive functions of the pancreas and traps bacteria in the lungs resulting in recurrent infections, and leads to irreversible damage. Lung failure is the major cause of death for someone with cystic fibrosis. From birth, a person with cystic fibrosis undergoes constant medical treatments and physiotherapy.
Cystic Fibrosis Transmembrane Regulator (CFTR)
The CFTR gene regulates how salt and water is moved in and out of the cell. In people living with cystic fibrosis, there is a genetic variation to the CFTR gene, where the protein does not form correctly. This means that salt and water can not optimally flow into or out of the cell, causing the outside of the cells to become dry and dehydrated.
The variation leads to an abnormally thick, dry and sticky mucus building up in the lungs, airways and digestive system in the body. This mucus causes blockages and makes a person much more susceptible to bacteria and virus getting caught up in the mucus leading to infections particularly in the lung.
The diagram to the left displays the regular function of the CFTR.
There are 5 main variations to the CFTR gene, each affecting different stages of the CFTR gene function. To learn more about these variations, visit our CFTR Variant Classes Poster.
In healthy lungs, a thin layer of mucus traps dirt and bacteria so that the body can move them out of the lungs.
For people with cystic fibrosis their mucus is much thicker and stickier and it can clog the lungs and airways. This mucus is hard to clear from the lungs, so it can trap bacteria which can lead to lung infections. Persistent coughing is common among those with cystic fibrosis.
People with cystic fibrosis may have reduced lung function due to the thickening of the walls of the airways, narrowing of the airways, damage to the airways and obstruction of the airways with mucus.
The digestive system
The pancreas produces digestive enzymes which help the body digest food by breaking down fats, proteins and carbohydrates.
The thick mucus that people with cystic fibrosis have blocks the ducts that carry the enzymes from the pancreas to the digestive system, causing what is known as pancreatic insufficiency. People who are pancreatic insufficient need to take enzyme medications to assist their digestion.
People with cystic fibrosis have difficulty in digesting fats which makes it harder to maintain weight. They also lose higher levels of salt in their sweat, therefore need a diet that is higher in fats, salt and kilojoules to compensate for this. They may also experience greasy and bulky stools and difficult bowel movements.
About one-third of all people with cystic fibrosis also are affected by a form of diabetes called cystic fibrosis related diabetes (CFRD), where their mucus prevents the pancreas from producing enough insulin. CFRD can be managed by monitoring blood-sugar levels and through using insulin.
Chiefly among other symptoms, cystic fibrosis can affect bone density, the liver and cause fertility problems in both women and men.