Cystic fibrosis explained: causes, care and new treatments

What cystic fibrosis is

Cystic fibrosis is caused by a fault in a single gene that controls how salt and water move in and out of cells. When that gene does not work properly, the body produces thick, sticky mucus instead of the thin, slippery kind. This mucus clogs the lungs and blocks the tubes that carry digestive juices from the pancreas to the gut. To be born with cystic fibrosis, a child must inherit a faulty copy of the gene from both parents, who are usually healthy carriers with no symptoms. It is not caused by anything the parents did, and it cannot be caught from another person.

How it affects the body

In the lungs, sticky mucus is hard to clear and traps bacteria, leading to repeated chest infections that gradually damage the airways over years. This causes a persistent cough, wheezing and breathlessness. In the digestive system, thick secretions block the pancreas so that enzymes cannot reach food, making it hard to absorb fat and nutrients; this can cause poor weight gain, greasy stools and vitamin shortages. Cystic fibrosis can also affect the liver, the sinuses, the bones and fertility, and many people develop a form of diabetes over time. Because it touches so many systems, care needs a whole team rather than a single specialist.

Diagnosis and monitoring

In the UK, most babies are picked up soon after birth through the newborn blood spot (heel prick) screening test, which flags those who need further checks. Diagnosis is then confirmed with a sweat test, which measures the amount of salt in the sweat, and often genetic testing to identify the exact gene faults. People with cystic fibrosis are cared for at specialist centres, where they are seen regularly to monitor lung function with breathing tests, track weight and nutrition, and check for infections and complications. Regular review lets the team act early — treating infections promptly and adjusting therapy — rather than waiting for problems to become severe.

Everyday treatment and care

Day-to-day care aims to keep the lungs clear and nutrition strong. Airway clearance — physiotherapy techniques and breathing exercises, sometimes with devices — helps shift mucus, often alongside inhaled medicines that thin secretions and open the airways. Chest infections are treated promptly with antibiotics. Because the pancreas is blocked, most people take enzyme supplements with meals to digest food, along with extra vitamins and a high-energy diet. Exercise is strongly encouraged because it helps clear the lungs and maintain fitness. Avoiding cross-infection matters too, which is why people with cystic fibrosis are asked not to meet each other in person. Care is coordinated by a specialist multidisciplinary team.

Modulator therapies and the changing outlook

The biggest recent change is a group of medicines called CFTR modulators. Rather than only treating symptoms, these target the faulty protein itself, helping it work better so that mucus becomes less thick. For the many people whose gene fault responds, these treatments can improve breathing, reduce infections and support weight gain, and they have contributed to a marked improvement in health and life expectancy. They do not suit everyone, and physiotherapy, enzymes and infection control remain essential. Research continues, including work aimed at people whose gene faults are not yet treatable this way. With modern care, many people with cystic fibrosis now live active adult lives.