Cystic fibrosis has changed more in the past decade than in the previous fifty years combined. For families receiving a diagnosis now – often at newborn screening before a child is even symptomatic – the landscape is profoundly different from what parents of CF children were told a generation ago. The life expectancy projections that shaped how CF was understood and communicated have had to be substantially revised upwards.
This doesn't mean CF is now a straightforward condition. Daily treatment remains demanding: physiotherapy, nebulisers, medications, clinic appointments, and the vigilance required around infections are a permanent feature of life. But the trajectory has changed in a way that is genuinely important for families to understand from the outset.
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What Cystic Fibrosis Is
CF is caused by mutations in the CFTR gene (cystic fibrosis transmembrane conductance regulator), located on chromosome 7. CFTR encodes a protein that acts as a chloride channel in cell membranes; without normal CFTR function, salt and water balance across epithelial cell surfaces is disrupted, leading to abnormally thick and sticky mucus in the airways, gut, and other organs.
CF is autosomal recessive: a child needs to inherit a defective copy from both parents to be affected. In the UK, around 1 in 25 people carries a single CF gene mutation without any health effects. The chance of two carriers having an affected child is 1 in 4.
There are over 2,000 known CFTR mutations. The most common in the UK is F508del (also written delta F508), which accounts for around 85-90% of CF alleles in the UK population. This distinction matters for treatment: CFTR modulator therapy targets specific mutations, and eligibility depends on which mutations a child carries.
How It Is Diagnosed
Since 2007, CF has been included in the newborn bloodspot screening programme in England, Scotland, Wales, and Northern Ireland. The screening test measures immunoreactive trypsinogen (IRT), a pancreatic enzyme that is elevated in CF; an elevated result triggers DNA analysis. The sensitivity of the combined IRT and DNA testing is around 95-99%, meaning the vast majority of affected infants are detected before symptoms begin.
Before screening was introduced, diagnosis typically followed repeated chest infections, failure to thrive, a parent noticing that their child tasted salty, or meconium ileus at birth (intestinal obstruction from thick meconium, occurring in around 10-20% of CF-affected newborns). Some children are still diagnosed through these symptomatic presentations – either because the mutation was missed by screening or, in some cases, because symptoms suggest the diagnosis in older children from non-UK backgrounds.
The diagnostic gold standard is the sweat test: a pilocarpine-stimulated collection of sweat that measures chloride concentration. Chloride above 60 mmol/L on two occasions confirms CF; 30-59 mmol/L is borderline and requires further evaluation. Genetic testing confirming two CFTR mutations on separate chromosomes also confirms the diagnosis.
The Main Effects of CF
The lungs are the primary site of damage in CF. Thick mucus impairs mucociliary clearance – the normal mechanism by which the airways remove bacteria and debris – leading to chronic bacterial colonisation, recurrent infections, and progressive inflammation. The bacteria that colonise CF airways are different from those that cause common pneumonias: Staphylococcus aureus and Haemophilus influenzae are common in younger children, but the appearance of Pseudomonas aeruginosa – typically in older children and adults – marks an important step in the natural history. Pseudomonas is difficult to eradicate once established, and its presence accelerates lung decline.
The pancreas is affected in about 85% of people with CF: thick secretions block the pancreatic ducts, leading to pancreatic exocrine insufficiency (inability to produce digestive enzymes). This means fat and protein are not properly absorbed, leading to steatorrhoea (fatty, oily stools), poor weight gain, and nutritional deficiencies. Treatment with pancreatic enzyme replacement therapy (PERT – Creon is the most common preparation in the UK) is given with every meal and snack.
The liver is involved in around 5-10% of people with CF, with cirrhosis possible in a minority. The gut is affected beyond the pancreas: CF-related liver disease and meconium ileus equivalent (an adult equivalent of the newborn intestinal obstruction) are recognised complications. Around 97% of men with CF are infertile due to absence of the vas deferens.
Daily Treatment Before the Modulator Era
Daily airway clearance physiotherapy has been the cornerstone of CF management for decades and remains so, even in the modulator era. The goal is to loosen and clear mucus from the airways before it becomes a site for bacterial growth. Various techniques are used: the Active Cycle of Breathing Technique (ACBT), the Autogenic Drainage technique, oscillating positive expiratory pressure (PEP) devices (Flutter, Acapella, AeroBika), and high-frequency chest wall oscillation vests. The technique used depends on age, ability, and which the child and family find effective and can sustain.
Nebulised medications are used routinely: hypertonic saline (6-7%) draws water into the airways and thins mucus; DNase (dornase alfa, or Pulmozyme) breaks down DNA released from dead inflammatory cells, which is a major component of CF mucus; nebulised antibiotics (tobramycin, colistin, aztreonam) are used to control chronic Pseudomonas colonisation.
Nutrition is a full clinical focus in CF: high-calorie intake is required to compensate for the energy cost of chronic inflammation and infection, and for malabsorption. Gastrostomy feeding is sometimes used to supplement oral intake in those who can't meet their nutritional needs.
CFTR Modulators: The Transformation
CFTR modulators are small molecules that target the defective CFTR protein rather than treating the consequences of defective function. They represent a fundamental shift in CF treatment philosophy.
The first modulator, ivacaftor (Kalydeco), was approved in 2012 for people with specific "gating" mutations (particularly G551D). In those patients – around 5% of the CF population – the effect was striking: lung function improved significantly, exacerbation rates fell, and weight improved.
The triple combination modulator Kaftrio (elexacaftor/tezacaftor/ivacaftor) was approved in the UK by NICE in 2020 and extended to children aged 6-11 in 2022. It is effective for people with at least one copy of the F508del mutation – covering 85-90% of people with CF in the UK. Clinical trial data, including the phase 3 trial by Heijerman and colleagues published in the Lancet in 2019, showed a mean improvement in FEV1 (lung function) of 14 percentage points compared with placebo, with dramatic reductions in pulmonary exacerbation rates and in sweat chloride.
The real-world impact has been substantial. CF Trust data from UK centres show that people starting Kaftrio are experiencing fewer hospitalisations, reduced sputum production, improved quality of life, and in some cases a reduction in chronic infection load. Projections for life expectancy – previously around 40-50 years for those born in the 1990s – are now expected to be substantially better for those who benefit from modulator therapy.
Kaftrio is not effective for the 10-15% of people with CF whose mutations are not responsive to available modulators. Research into treatments for these mutations (including gene therapy approaches) is ongoing.
Life with CF
Families of children with CF manage a daily treatment burden that is substantial: physiotherapy sessions (often 20-30 minutes, twice daily), nebuliser treatments, medication doses with every meal, regular clinic appointments, and heightened vigilance around infections. Cross-infection between people with CF is a genuine risk, because the organisms that colonise CF airways can transfer between patients; all CF centres in the UK have protocols that prevent patients from being in the same clinical space at the same time.
School life requires planning: ensuring PERT is available at mealtimes, managing physiotherapy around school schedules, and helping teachers and peers understand the condition without the child feeling singled out. Teenagers with CF face particular psychological challenges: managing a visible and demanding illness during an age when fitting in is paramount, and coming to terms with the long-term implications of the diagnosis.
The Cystic Fibrosis Trust is the UK's main charity for CF, providing support for families, funding research, and advocating for treatment access. Their parent resources and forum are genuinely useful for newly diagnosed families.
Key Takeaways
Cystic fibrosis (CF) is the most common life-limiting inherited condition in the UK, affecting around 10,800 people. It is caused by mutations in the CFTR gene, which controls chloride transport across cell membranes; defective CFTR leads to thick, sticky mucus affecting the lungs, digestive system, and other organs. Most cases are now detected through the newborn bloodspot screening programme. The introduction of CFTR modulator therapy – particularly the triple combination drug Kaftrio (elexacaftor/tezacaftor/ivacaftor) – has transformed outcomes for the 85-90% of people with CF who have the F508del mutation, with significant improvements in lung function and life expectancy now expected.
