Cystic Fibrosis

Meet the patient

:A 24-year-old electrician lands in your respiratory clinic with a decade of daily green sputum, two pneumonias a year, and clubbing you can see from the door. His CT shows diffuse bronchiectasis; his BMI sits at 18 despite a ravenous appetite and greasy stools. He is here only because the fertility clinic, working up his absent vas deferens, finally asked the question nobody else did. [4]

The thread that joins his lungs, his gut and his reproductive tract is the thread that runs through every cystic fibrosis case: one gene, many organs — and the sweat chloride confirms it. Hold that frame and the whole topic — the anion channel, the microbiological succession, the modulator ladder — falls into place. [2]

One broken channel, many damaged organs — and it is now a disease of adults

Cystic fibrosis is one broken anion channel — and, since the modulators arrived, increasingly a disease you meet in adults, not just children. [4]

Cystic fibrosis is the most common life-limiting autosomal recessive disorder in populations of European ancestry (about 1 in 2500 livebirths), caused by loss-of-function mutations in the CFTR gene on chromosome 7. The gene product, the cystic fibrosis transmembrane conductance regulator, is a chloride-conductance channel that regulates anion transport and mucociliary clearance on the apical membrane of epithelial cells in the airways, pancreas, intestine, biliary tree, sweat glands and vas deferens. When CFTR fails, mucus retention and chronic infection follow, with local airway inflammation that progressively damages the lungs. [27] [28] [4]

Etymology for viva gold: F508del is literal — a deletion of F (phenylalanine, the single-letter amino-acid code) at position 508 of the CFTR protein, the mutation classically written ΔF508. Read the mutation name and the molecular lesion is already in front of you. [28]

The clinical face of CF is therefore relentlessly multi-system. Lung disease — chronic bacterial endobronchitis with Staphylococcus aureus and then Pseudomonas aeruginosa, progressing to bronchiectasis and respiratory failure — dominates the prognosis and is the focus of most therapy. Pancreatic exocrine insufficiency is a defining feature of the classic phenotype and produces steatorrhoea, failure to thrive and fat-soluble vitamin deficiency; progressive endocrine loss causes CF-related diabetes (CFRD) in about 20 percent of adolescents and 40 to 50 percent of adults. Meconium ileus and distal intestinal obstruction syndrome (DIOS) reflect gut involvement; focal biliary cirrhosis, gallstones and the absent vas deferens (the organ most sensitive to reduced CFTR function) complete the picture. [29] [4] [9]

Two decades ago median survival barely exceeded 30 years. The arrival of CFTR modulators — small molecules that restore CFTR function at the protein level — has transformed CF into a chronic disease of adults: median life expectancy is now older than 40 years and rising. The triple combination elexacaftor-tezacaftor-ivacaftor (Trikafta in the US, Kaftrio in Europe) is effective in nearly nine out of ten patients (all who carry at least one Phe508del allele) and is standard of care for F508del homozygotes and for compound heterozygotes carrying one F508del plus one minimal-function allele. [4] [3] [2] In countries with modulator access the focus of CF care is shifting from delaying death to preserving quality of life, mental health and reproductive choice. [4]

Six mutation classes — and the class picks both the severity and the drug

You classify a CFTR mutation by what it does to the protein, not where it sits on the gene — because the functional class sets both the phenotype and which modulator will work. [17]

[17] [29]

A single patient inherits two CFTR alleles, and the combination — not either allele alone — writes the phenotype. Most patients are compound heterozygotes: F508del on one chromosome plus a gating or minimal-function variant on the other. Always consult the CFTR2 database for variant-specific disease liability and modulator eligibility before you commit to a drug. [15]

When only one organ speaks — CFTR-related disorder

Everyone forgets: partial CFTR dysfunction does not always mean classic CF. A class IV, V or VI variant can surface as a CFTR-related disorder instead — isolated CBAVD with adult-onset respiratory symptoms, recurrent or chronic pancreatitis, or bronchiectasis without the full phenotype. A CFTR-related disorder is "a clinical entity associated with CFTR dysfunction that does not fulfil diagnostic criteria for CF", and consensus algorithms use sweat testing, mutation analysis, nasal potential difference and intestinal current measurement to draw the line. [10]

The classic trap: a man presenting with CBAVD and adult-onset bronchiectasis may carry a single CFTR mutation and have a CFTR-related disorder, not classic CF — always sweat-test and genotype before you label him. [10]

Who gets it — and why newborn screening changed everything

CF is overwhelmingly a disease of European ancestry — and the single biggest change in who you actually meet is universal newborn screening. [27] [4]

[27] [3] [9] [21] [4]

CF is overwhelmingly a disease of European ancestry, and CFTR mutant alleles show wide heterogeneity across world populations, with DeltaF508 the most common mutation in most. The single most important epidemiological advance of the past two decades has been universal newborn screening (NBS) in high-income countries: infants with a high immunoreactive trypsinogen (IRT) level proceed to further testing, and a positive screen with two CFTR mutations is confirmed with a sweat test. NBS and early specialist care have shifted diagnosis from the symptomatic toddler with failure to thrive to the asymptomatic neonate, and have improved long-term nutritional and pulmonary outcomes. [28] [29] [5]

The principal risk factor for disease is parental carrier status (genetic counselling for siblings and at-risk couples); consanguinity increases risk where the variant is local. Chronic Pseudomonas aeruginosa infection, malnutrition, CFRD and environmental exposures such as tobacco smoke are associated with more rapid decline. Socioeconomic deprivation amplifies each of these. [4]

The molecular lesion — chloride out, mucus like glue

Lose CFTR and one thing happens at the airway surface: the hydration layer fails. That single fact explains every organ CF damages. [4]

Normal airway epithelium keeps its surface liquid hydrated so that ciliary beating can sweep mucus and trapped pathogens upward. CFTR is an ion channel crucial for correct ion and fluid transport across epithelial cells. When CFTR is absent or dysfunctional: [4]

• Anion and fluid transport fail → secretions become dehydrated, viscous and adherent.
• The periciliary liquid layer collapses, cilia lie flat in viscous mucus, and mucociliary clearance grinds to a halt.
• Retained, dehydrated mucus plugs small airways; identification of pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus in respiratory samples is integral to CF, and infection becomes chronic.
• A self-perpetuating cycle of mucus retention → chronic infection → airway inflammation → bronchiectasis establishes itself, often insidiously, from early infancy. [4] [29]

The same dehydrated-secretion mechanism damages other organs: thick pancreatic juice obstructs ducts and acini (exocrine and then endocrine loss); viscid meconium obstructs the terminal ileum (meconium ileus); inspissated bile produces focal biliary cirrhosis; and the vas deferens — the organ most sensitive to reduced CFTR function — fails to develop (CBAVD). Sweat glands lose CFTR-dependent function, giving the elevated sweat chloride that is the diagnostic cornerstone. [29] [4]

The microbiological succession — name the organism, name the decade

CF airway infection follows a sequence you can almost date by the patient's age — and the worst organism, Burkholderia, rewrites the transplant conversation. [29]

CF airway infection evolves in a recognisable sequence. Staphylococcus aureus dominates infancy and early childhood. Pseudomonas aeruginosa appears later — initially intermittent and treatable, then chronic within biofilm and essentially incurable, marking accelerated decline. Burkholderia cepacia complex infection modifies the disease phenotype and complicates care. Non-tuberculous mycobacteria and Aspergillus add further layers. [29] [4]

[29]

The classic trap: Burkholderia cepacia complex is not just another organism — it can complicate transplant candidacy. Identify it early and never let a cepacia-positive patient share clinical space with another CF patient. [29]

How they present — by the decade of life

Modern newborn screening means most patients are diagnosed before they have a symptom — but presentations still arrive at every age, and the atypical or CFTR-related case in adolescence and adulthood is the one you must not miss. [4] [5]

Neonate and infant

The neonate can announce CF from the gut before the lung ever does. [29]

• Meconium ileus — abdominal distension, bilious vomiting, failure to pass meconium, with microcolon and inspissated meconium pellets in the terminal ileum on contrast enema; meconium ileus is one of the suggestive signs that trigger diagnostic confirmation after newborn screening.
• Prolonged neonatal jaundice and cholestasis.
• Failure to thrive despite a ravenous appetite, frequent bulky greasy stools, rectal prolapse, salty-tasting skin, hypochloraemic metabolic alkalosis, electrolyte depletion in hot weather ("pseudo-Bartter"). [29] [4]

Child and adolescent

In the school-age child the lung takes over the story — and the clues cluster. [4]

• Chronic productive cough, recurrent wheeze, recurrent pneumonia or "asthma that doesn't respond".
• Bronchiectasis: daily purulent sputum, finger clubbing, coarse inspiratory crackles, wheeze, exertional dyspnoea.
• Nasal polyposis and chronic sinusitis in a child — a major clue.
• Malabsorption: steatorrhoea, distal intestinal obstruction syndrome (DIOS), failure to thrive, fat-soluble vitamin deficiencies (night blindness, rickets, easy bruising, neuropathy).
• CF-related diabetes typically emerges from about age 10 — weight loss, polyuria, polydipsia, and an unexplained decline in pulmonary function. [9]
• Delayed puberty, short stature, salty crusting on the skin after exercise. [4]

Adult

The adult with CF is now common — and the disease you meet at 30 is not the disease your textbooks described. [4]

• Chronic Pseudomonas bronchitis with frequent exacerbations; massive haemoptysis (about 4 percent of registry patients over a decade); pneumothorax; cor pulmonale in end-stage disease. [21] [30]
• CFRD in 40 to 50 percent of adults; osteoporosis; arthritis. [9]
• Infertility (CBAVD, the organ most sensitive to CFTR dysfunction, in most males; thickened cervical mucus in females) — often the presenting complaint in atypical or CFTR-related disease. [29]
• Mental health burden: depression, anxiety and treatment fatigue — screening for anxiety and depression in patients and caregivers is part of routine CF care. [29]

Focused bedside examination

What else looks like this — split by the presenting system

The differential splits by which door the patient walked through: chronic lung disease, malabsorption, neonatal bowel obstruction, or male infertility. [4]

Chronic respiratory disease with bronchiectasis:

• Primary ciliary dyskinesia (PCD) — situs inversus (Kartagener), chronic sinusitis, otitis media, neonatal respiratory distress, infertility; diagnosis by nasal nitric oxide (low) and electron microscopy of cilia.
• Primary immunodeficiency — common variable immunodeficiency, IgA deficiency, X-linked agammaglobulinaemia; recurrent sinopulmonary infection with low immunoglobulins.
• Post-infectious bronchiectasis — pertussis, measles, adenovirus, severe pneumonia in childhood.
• Allergic bronchopulmonary aspergillosis (ABPA) — overlapping clinical, radiographic, microbiologic and immunologic features make it particularly hard to separate from CF lung disease. [24]
• Tuberculosis — epidemiological risk, upper-lobe cavitation, positive sputum AFB.
• Foreign-body aspiration — unilateral fixed wheeze, regional hyperinflation.
• Asthma with chronic infection — atopy, reversibility, normal sweat chloride. [4]

Malabsorption and failure to thrive:

• Shwachman-Diamond syndrome — exocrine pancreatic insufficiency, neutropenia, skeletal dysplasia; sweat chloride normal.
• Coeliac disease, chronic pancreatitis, short-bowel syndrome, biliary atresia, protein-losing enteropathy. [4]

Neonatal bowel obstruction (differential of meconium ileus):

• Meconium plug syndrome (small left colon, often with maternal diabetes).
• Intestinal atresia, Hirschsprung disease, malrotation with volvulus, imperforate anus. [4]

Male infertility with CBAVD:

• Isolated CBAVD may be a CFTR-related disorder even without classic CF — consensus guidelines exist precisely to classify such patients. Always genotype and offer sweat testing in men presenting with CBAVD. [10]

The clinic visit — every organ, every time

A CF review is a whole-body exercise at every visit — the lung is the headline but never the whole story. [4]

• History. Neonatal (meconium ileus, NBS result, weight trajectory); respiratory (cough character, sputum volume and colour, exacerbation frequency, hospitalisations, ICU admissions, haemoptysis, pneumothorax); gastrointestinal (stool pattern, malabsorption, DIOS, rectal prolapse, liver disease); endocrine (CFRD symptoms, polyuria, polydipsia); ENT (nasal polyps, sinusitis); reproductive (fertility, contraception, pregnancy plans); social (school, work, exercise, smoking, alcohol, mental health, adherence, financial); family (siblings, carrier testing, consanguinity); medicines (modulator, nebulised therapies, antibiotics, PERT dose and timing, vitamins); vaccination history; infection history by organism with dates of acquisition. [4] [29]

• Examination. Vital signs including SpO₂ on room air; growth — height, weight, BMI, growth velocity; chest (deformity, crackles, wheeze, hyper-resonance); abdomen (hepatosplenomegaly, mass); ENT (polyps); skin (salty crust, clubbing, cyanosis, injection sites, eczema); musculoskeletal (kyphoscoliosis, joint disease); mental state. [4]

• Functional status. Spirometry trend (FEV1 is the key prognostic metric); symptom-based quality-of-life scores (CFQ-R); depression and anxiety screening annually. [29] [1]

Confirming the diagnosis — sweat chloride over sixty, then genotype

Diagnostic tests

The diagnostic triad is the spine: a compatible phenotype (or positive newborn screen), evidence of CFTR dysfunction on sweat testing, and two disease-causing CFTR mutations — the 2017 CFF consensus fixes the algorithm. [5]

[29] [5] [15]

Routine monitoring battery

The annual review interrogates every organ system — lung, gut, endocrine, bone, microbe, reproductive. [4]

Respiratory:

• Spirometry at review — FEV1 percent predicted is the single most important prognostic metric; track the trajectory.
• Sputum or respiratory cultures at every visit — identification of pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus is integral to CF management; treat new organisms aggressively. [29]
• Chest imaging to characterise structural change (bronchiectasis, mucus plugging, air trapping). [29]
• Arterial blood gas in advanced disease; respiratory failure remains a characteristic complication of late CF. [30]

Gastrointestinal and nutritional:

• Faecal pancreatic elastase to classify pancreatic exocrine status (insufficiency is part of the classic phenotype).
• Liver function tests with imaging surveillance for CF liver disease. [4]
• Growth and weight-status monitoring using registry-based normative data — a CFF evidence-based recommendation. [16]

Endocrine and metabolic:

• Oral glucose tolerance test annually from age 10 for CFRD screening; HbA1c alone is not recommended as a screening test. [9]
• Vitamin status on pancreatic-insufficient patients — nutrition guidelines address micronutrient monitoring. [16]

Microbiological:

• ABPA surveillance — recognised by overlapping clinical, radiographic, microbiologic and immunologic features (including total IgE) per the CFF consensus conference; distinguishing ABPA from CF lung disease is deliberately criteria-based. [24]
• Respiratory microbiology including mycobacterial and fungal targets when clinically indicated. [29]

Reproductive:

• Fertility discussion in adolescents and adults (CBAVD); offer genetic counselling. [10] [4]

Why does sweat chloride rise in CF?

In a normal sweat gland, CFTR on the reabsorptive duct handles chloride (and sodium follows), so surface sweat stays relatively salt-poor; sweat secretion through beta-adrenergic pathways is CFTR-dependent and is diminished or absent in CF. In CF, CFTR-dependent sweat gland function fails, so sweat emerges with elevated chloride and sodium concentrations — a hallmark diagnostic feature, with values over 60 mmol/L indicating CFTR dysfunction. The same channel defect that dehydrates airway secretions leaves the duct unable to reclaim salt.

[29] [4]

When CF decompensates — airway, antibiotics, nutrition

Most CF emergencies are pulmonary, and the bundle is always the same shape: antibiotics guided by the last sputum, intensified airway clearance, nutritional support, and anticipation of complications. [4]

Acute pulmonary exacerbation

An exacerbation is a change from the patient's baseline — and fever is often absent, so do not wait for it. Think increased cough, sputum volume or purulence, dyspnoea, fatigue, falling exercise tolerance, weight loss and new crackles; in the pivotal trials an exacerbation was defined by respiratory symptoms requiring parenteral (IV) antibiotics. [8]

Immediate management:

• IV antibiotics guided by the most recent sputum cultures — active against the patient's known organisms (a beta-lactam plus an aminoglycoside is the classic anti-pseudomonal combination for Pseudomonas; adjust to sensitivities for MRSA or Burkholderia).
• Intensified airway clearance — increase physiotherapy frequency; continue home nebulised mucolytics (dornase alfa, hypertonic saline) with bronchodilator pre-treatment. [6]
• Nutritional support — maintain or increase caloric intake, continue PERT, and give fat-soluble vitamins; the CFF nutrition recommendations cover energy needs and enzyme dosing. [16]
• Oxygen for hypoxaemia; bronchodilators before physiotherapy and hypertonic saline. [6]
• Screen for CFRD — patients with acute pulmonary exacerbation requiring IV antibiotics should have glucose monitoring; the OGTT remains the screening test of choice. [9]
• Disposition: hospitalise for moderate-severe exacerbations; selected mild exacerbations can finish IV therapy at home with reliable support. [8]

Massive haemoptysis

Massive haemoptysis is large-volume or recurrent life-threatening bleeding — it occurs in about 4 percent of registry patients over a decade (roughly 1 in 100 each year), afflicts older patients with severe lung disease, and carries attributable mortality. The answer is embolisation. [21]

• Protect the airway: high-flow oxygen; secure IV access; correct coagulopathy and transfuse as needed.
• Treat the driving exacerbation with antibiotics. [8]
• Bronchial artery embolisation (BAE) by interventional radiology is the initial treatment for massive haemoptysis — immediate success in 98 percent in the largest paediatric series, with about half of embolised children needing a repeat procedure over time. [22]
• Surgical resection is reserved for refractory localised bleeding after failed embolisation. [30]

Pneumothorax in CF

A pneumothorax in CF marks advanced disease — drain it when large or symptomatic, and talk to the transplant centre before definitive pleurodesis. [30]

Pneumothorax remains one of the characteristic pulmonary complications of advanced CF alongside massive haemoptysis and respiratory failure; modern reviews describe drainage for large or symptomatic events and definitive recurrence-prevention (pleurodesis) once the acute episode is controlled — with the caveat that transplant candidacy should be discussed before definitive pleural symphysis, which complicates future transplant surgery. [30]

Distal intestinal obstruction syndrome (DIOS)

DIOS is right iliac fossa pain with a palpable mass and obstruction — rehydrate, give stool-softening laxatives or gut lavage, and reserve surgery for disaster. [12]

• Rehydration (IV fluids) combined with stool-softening laxatives or gut lavage with balanced electrolyte solutions — the core of guideline management; beware rapid fluid shifts after osmotic agents. [12]
• Diagnosis rests on suggestive symptoms with a right lower quadrant mass confirmed on imaging; the main differential is chronic constipation, and DIOS is mainly seen in pancreatic-insufficient patients with a history of meconium ileus or previous DIOS. [12]
• Surgery is reserved for failed medical therapy, perforation, or peritonitis — a last resort given the morbidity in CF. [12]
• Prevent recurrence: avoid dehydration and optimise pancreatic enzyme dosage; prophylactic laxative therapy is widely used but not evidence-based. [12]

The treatment stack — modulator, clearance, antibiotic, nutrition

Modern CF care is a multidisciplinary stack, layered one therapy on the next: a modulator for the molecular defect, clearance and mucolytics for the mucus, inhaled antibiotics and a macrolide for the infection, nutrition for the body, and aggressive treatment of each complication as it arrives. [4]

1. CFTR modulator therapy — the foundation

The modulators are the single greatest advance in CF history — and they are mutation-directed, not phenotype-directed: you match the drug to the class. [17] [20]

[1] [14] [18] [19] [2] [3] [2] [3]

Citations: [1] (ivacaftor); [14] (lumacaftor-ivacaftor); [18] [19] (tezacaftor-ivacaftor); [2] [3] (elexacaftor-tezacaftor-ivacaftor).

2. Airway clearance and mucolytics

• Chest physiotherapy — an individualised, regular airway-clearance regimen (technique chosen by patient preference and age) is the backbone of daily care; intensify during exacerbations. [4]
• Dornase alfa (Pulmozyme, recombinant human DNase) — nebulised once daily; it reduces the viscoelasticity of purulent CF secretions. The 1994 Fuchs trial (968 patients, 24 weeks) showed a 28 percent reduction in the risk of respiratory exacerbations with once-daily rhDNase (37 percent twice daily) and an FEV1 improvement of about 5.8 percent. [8]
• Hypertonic saline 7 percent — 4 mL nebulised twice daily for 48 weeks, with a bronchodilator given before each dose; the Elkins 2006 NEJM trial showed significantly higher FVC (by 82 mL) and FEV1 (by 68 mL) values and 56 percent fewer pulmonary exacerbations (relative reduction) than control saline, with no worsening of infection or inflammation. [6]
• Inhaled mannitol (dry powder, 400 mg twice daily) — an osmotic alternative: in the phase 3 trial (324 patients, 26 weeks) FEV1 improved by 92.9 mL, with benefit whether or not patients were also on rhDNase. [25]

3. Anti-infective therapy

[7] [13] [11] [26]

Citations: [7] (inhaled tobramycin); [13] (aztreonam lysine); [11] (azithromycin); [26] (early anti-pseudomonal treatment).

Infection control on wards and clinics — strict cohort segregation by organism (Pseudomonas, B. cepacia, MRSA), hand hygiene, single rooms where possible, dedicated equipment per patient. B. cepacia complex patients should never share clinical space with other CF patients. [29]

4. Anti-inflammatory and bronchodilator therapy

• Bronchodilators — a bronchodilator is given before each hypertonic-saline dose (it is irritant) and before physiotherapy; add regular long-acting bronchodilator where there is a reversible component. [6]
• Systemic corticosteroids — short courses for severe exacerbations or ABPA; avoid chronic oral steroids. The CFF consensus conference on ABPA in CF addresses corticosteroid- and antifungal-based treatment approaches explicitly — treat ABPA per consensus criteria. [24]
• High-dose ibuprofen — in a propensity-matched registry cohort of children, high-dose ibuprofen use was associated with a 37.5 percent slower FEV1 decline and better long-term survival; it remains an option in children with preserved lung function where monitoring is feasible. [23]

5. Nutritional and pancreatic support

Aim for caloric intake above standard requirements, with pancreatic enzyme replacement and fat-soluble vitamin supplementation — the CFF evidence-based nutrition recommendations cover energy intake, PERT dosing and growth monitoring. [16]

• Pancreatic enzyme replacement therapy (PERT) — enteric-coated microspheres with every meal and snack; dose is individualised and titrated to symptoms, growth and fat absorption; the CFF systematic review sets out evidence-based dosing recommendations. [16]
• Fat-soluble vitamins — A, D, E and K supplementation in pancreatic-insufficient patients, with laboratory monitoring per the nutrition guidelines. [16]
• Growth and weight-status monitoring — registry-based normative data guide targets; a falling BMI or weight trajectory is a poor prognostic sign and should trigger nutritional review. [16]
• Caloric supplementation — oral high-calorie supplements, then enteral tube feeding if oral intake cannot maintain growth and weight status. [16]

6. Cystic fibrosis-related diabetes

CFRD is the commonest comorbidity of adult CF — about 20 percent of adolescents and 40 to 50 percent of adults — and it is neither type 1 nor type 2: primarily insulin insufficiency with fluctuating insulin resistance, it tracks with pulmonary decline, and the additional diagnosis worsens pulmonary function and survival. [9]

• Screen with a 2-hour 75-g OGTT annually from age 10; HbA1c performs too poorly to be recommended as a screening test. [9]
• Treat with insulin, not metformin alone — insulin is the standard medical therapy for CFRD. [9]
• Coordinate insulin timing with PERT and meals. [16]
• Re-screen with OGTT during acute pulmonary exacerbation requiring IV antibiotics and during systemic glucocorticoid treatment. [9]

7. Hepatobiliary and bone disease

• Liver — CF liver disease (focal biliary cirrhosis, portal hypertension, gallstones) is part of the multi-system phenotype; monitor liver function and imaging at annual review and involve hepatology for portal hypertension and decompensation. [4]
• Bone — CF low bone mineral density and fragility fracture risk accompany advanced disease; nutrition guidelines cover vitamin D and calcium status in pancreatic insufficiency, with DEXA and specific therapy guided by specialist protocols. [16] [4]

8. Reproductive and mental health

• Males — CBAVD (the vas deferens is the organ most sensitive to reduced CFTR function) causes infertility; classify isolated CBAVD as a possible CFTR-related disorder and arrange genotype-guided counselling and assisted-reproduction referral. [29] [10]
• Females — pregnancy is increasingly common as survival improves; preconception counselling should optimise lung function, nutrition and CFRD. [4]
• Mental health — screening for anxiety and depression in patients and their care partners is recommended, with pharmacological and psychological treatment when identified. [29]

9. Lung transplantation

Bilateral sequential lung transplant is the end-game option for end-stage disease — and is increasingly deferred because the modulators are keeping people off the list. [4]

Bilateral sequential lung transplantation is offered for end-stage disease; timing follows transplant-programme criteria, and modulator therapy is reshaping the referral landscape. [4]

• Indications: advanced respiratory failure despite optimised therapy; refractory complications such as recurrent massive haemoptysis; declining functional status. [30]
• Contraindications (centre-dependent) — multiply resistant organisms with no post-transplant antibiotic options, severe malnutrition, non-adherence, active malignancy.
• Outcomes — transplantation extends survival and improves quality of life in end-stage CF; CFTR modulators are expected to reduce transplant need further as the treated population ages. [4] [30]

Stepwise care at a glance

The subtypes and scenarios that bite

• F508del homozygous CF — classic severe multisystem phenotype; eligible for elexacaftor-tezacaftor-ivacaftor from age 12 in the pivotal trial (label ages have since extended). [2]
• Compound heterozygous Phe508del + minimal-function allele — also eligible for triple therapy; Middleton 2019 demonstrated comparable benefit. [3]
• Gating mutations (G551D) — class III; ivacaftor monotherapy is highly effective (Ramsey 2011). [1]
• Residual-function heterozygotes (Phe508del + residual-function allele) — tezacaftor-ivacaftor (or ivacaftor alone) is efficacious (Rowe 2017, EXPAND). [19]
• Atypical / CFTR-related disorder — late presentation with isolated CBAVD, chronic pancreatitis or bronchiectasis; classify per consensus criteria with sweat testing, genotyping, NPD/ICM. [10]
• DIOS in adults — rehydration plus stool softeners or gut lavage; optimise enzyme dose to prevent recurrence. [12]
• Allergic bronchopulmonary aspergillosis — recognise by consensus criteria (overlapping clinical, radiographic, microbiologic and immunologic features, including immunologic markers such as total IgE); treat per the CFF consensus approach with corticosteroid- and antifungal-based regimens. [24]
• CF in pregnancy — preconception optimisation (FEV1, BMI, CFRD) with MDT care; modulator risk/benefit is individualised. [4]
• Post-lung-transplant CF — immunosuppression, infection prophylaxis, ongoing management of extrapulmonary CF (PERT, CFRD, fertility, bone). [30]

How CF patients come to harm — by system

[21] [9] [29] [4] [30]

Common pitfalls:

• Misdiagnosing atypical CF as "asthma plus malabsorption" or "idiopathic bronchiectasis" — always sweat-test and genotype a child with chronic productive cough, nasal polyps and clubbing, and any man with CBAVD. [29] [10]
• Missing CFRD — HbA1c alone is insufficient; annual OGTT from age 10 is the recommendation. CFRD heralds pulmonary decline. [9]
• Inadequate nutritional rescue — every exacerbation should trigger a nutritional review; growth and weight status must be tracked against registry norms. [16]
• Person-to-person transmission — never mix B. cepacia–positive patients with other CF patients in clinics or wards. [29]

The trajectory has been rewritten — but only where modulators reach

Where modulators and modern multidisciplinary care reach, median life expectancy is now older than 40 years and climbing. Survival is set by: [4]

• Genotype and modulator eligibility — F508del homozygous and Phe508del-minimal-function genotypes gain the most from triple therapy. [2] [3]
• Age at diagnosis and early care — NBS-detected infants have better growth and pulmonary trajectories. [5]
• Microbiological history — chronic Pseudomonas and Burkholderia infection complicate the course. [29]
• Nutritional and metabolic status — BMI, CFRD. [16] [9]
• Adherence and psychosocial factors — nebulised therapies are burdensome; adherence shapes outcome.
• Socioeconomic and structural access — modulator access varies dramatically by country and reimbursement. [4]

Disposition — outpatient multidisciplinary care with annual review for stable patients; admission for exacerbations, complications and transplant workup. End-of-life and advance care planning run in parallel with transplant referral; palliative CF care remains essential for the non-modulator subset. [4] [30]

Special populations — neonate to transplant survivor

• Neonate — meconium ileus or a positive NBS triggers diagnostic confirmation; transfer to a specialist CF centre; start PERT if pancreatic insufficient; involve the family in early education. [29] [16]
• Child — growth and development are paramount; school support, family psychosocial input; transition preparation begins in early adolescence. [16]
• Adolescent and young adult — adherence is the central challenge; mental health screening; reproductive and fertility counselling; transition to adult CF services. [29]
• Pregnancy in CF — preconception MDT optimisation; modulator risk/benefit discussion; postpartum respiratory vigilance. [4]
• CF after lung transplant — immunosuppression, infection prophylaxis, ongoing extrapulmonary CF management. [30]
• End-of-life — palliative care integrated with disease-modifying therapy; symptom control; advance directives. [30]

The trials and guidelines that built the modern ladder

Landmark trials

[1] [2] [3] [14] [18] [19]

Citations for individual trials: [1] (Ramsey 2011 ivacaftor), [2] (Heijerman 2019), [3] (Middleton 2019), [14] (Wainwright 2015 lumacaftor-ivacaftor), [18] [19] (tezacaftor-ivacaftor).

Guidelines & registries

• Cystic Fibrosis Foundation (CFF) consensus statements — diagnosis (Farrell 2017), [5] CFTR modulator use (Ren 2018), [20] nutrition (Stallings 2008), [16] CFRD (Moran 2010), [9] DIOS (Colombo 2011), [12] CFTR-related disorders (Bombieri 2011), [10] ABPA (Stevens 2003). [24]
• European Cystic Fibrosis Society (ECFS) standards of care and ECFS Patient Registry — annual outcome reporting across Europe; ECFS standards are reflected in the diagnostic algorithms. [29]
• CFTR2 database (cftr2.org) — variant-specific disease liability and modulator response. [15]

Regional differences

[2] [3] [20] [29]

Controversies and future directions

• Modulator access and equity — between-country disparity in modulator access widens the survival gap. [4]
• Modulator therapy in pregnancy and the very young — long-term safety data are still accumulating; label ages continue to extend downward. [2] [3]
• Gene therapy and mRNA therapeutics — further small molecule and gene-based therapies are being developed to restore CFTR function. [4]
• ELX-TEZ-IVA for rarer mutations — extension studies continue to add variant indications. [3]
• Palliative care integration — evolving alongside modulator-driven survival gains. [30]

The exam pearls — the numbers you must reproduce

• CF = autosomal recessive, CFTR gene on chromosome 7; Phe508del is the most common mutation, and nearly 90 percent of patients carry at least one copy. [27] [3] [14]
• The CFTR defect is failed anion secretion → mucus retention → chronic infection → airway inflammation → bronchiectasis. [4]
• Sweat chloride over 60 mmol/L indicates CFTR dysfunction; equivocal values need repeat testing or extended CFTR analysis. [29]
• Microbiological succession: Staph aureus (early) → Pseudomonas aeruginosa (the key chronic pathogen) → Burkholderia cepacia complex and NTM complicate advanced disease. [29]
• Pancreatic exocrine insufficiency is a defining feature of classic CF; CFRD in about 20 percent of adolescents and 40 to 50 percent of adults; the vas deferens is the organ most sensitive to reduced CFTR function. [29] [9]
• Newborn screening = immunoreactive trypsinogen (IRT), with sweat-test confirmation. [5] [29]
• CFTR modulator classes: potentiator (ivacaftor — gating G551D); correctors (lumacaftor, tezacaftor, elexacaftor — F508del); triple therapy covers nearly 90 percent of patients (at least one Phe508del allele). [1] [3]
• Acute exacerbation = IV antibiotics guided by the most recent sputum (exacerbations were defined by the need for parenteral antibiotics in the trials), intensified airway clearance, nutritional support. [8]
• Dornase alfa neb once daily (28 percent lower exacerbation risk); hypertonic saline 7 percent, 4 mL twice daily with bronchodilator (56 percent fewer exacerbations); inhaled tobramycin 300 mg BD in 28-day cycles; aztreonam lysine 75 mg TDS for 28 days; azithromycin 250 mg (under 40 kg) or 500 mg three days weekly. [8] [6] [7] [13] [11]
• PERT with every meal and snack, dosed per CFF nutrition recommendations and titrated to growth and symptoms. [16]
• CFRD treated with insulin, NOT metformin alone; screen with OGTT annually from age 10 (HbA1c not recommended as screening). [9]
• Median life expectancy now over 40 years in countries with modern care. [4]

[27] [3] [29] [8] [6] [29] [5] [9]

The mantra

Sweat chloride over sixty, genotype to confirm, clear the airway every day — and a modulator if the genotype allows. [29] [15]

Ward-round test — three stems, thirty seconds each

Stem 1 — the neonate who never passed meconium (answer)

A term neonate has abdominal distension, bilious vomiting, and no meconium at 48 hours; contrast enema shows a microcolon and pellets in the terminal ileum. What is the diagnosis, the next test, and the principle of management? Model: This is meconium ileus — inspissated meconium obstructing the terminal ileum, one of the suggestive findings that trigger CF diagnostic work-up after newborn screening. Confirm CF with sweat chloride testing (the gold standard) plus CFTR genotyping, and check the newborn-screen result. Manage the obstruction with the contrast enema that is already defining the anatomy, reserving surgery for perforation, volvulus or atresia — involve paediatric surgery early. [29] [5]

Stem 2 — bronchiectasis and absent vas deferens (answer)

A 28-year-old man is referred for daily purulent sputum, clubbing, and CT-confirmed diffuse bronchiectasis; his fertility work-up shows congenital bilateral absence of the vas deferens. Sweat chloride is 38 mmol/L. What is going on, and what do you do next? Model: This is a CFTR-related disorder, not classic CF — reduced-function CFTR variants giving isolated CBAVD plus adult-onset bronchiectasis, with an equivocal sweat chloride. Do not dismiss him as 'idiopathic bronchiectasis'. The diagnostic algorithms recommend extended CFTR sequencing interpreted through the CFTR2 database, with nasal potential difference or intestinal current measurement when sweat testing and genotype disagree — an equivocal value does not exclude a CFTR-related diagnosis. Manage the bronchiectasis with airway clearance and aggressive infection control, and offer genetic counselling. [10] [15] [29]

Stem 3 — massive haemoptysis in established CF (answer)

A 32-year-old with known CF coughs up a large volume of bright red blood in an hour. What is your first move at the bedside, and what is the definitive treatment? Model: This is massive haemoptysis — a serious complication occurring in about 4 percent of registry patients over a decade, in older patients with severe lung disease, with attributable mortality. At the bedside: protect the airway, give high-flow oxygen, secure IV access, set up for transfusion, and treat the driving exacerbation with antibiotics. The definitive treatment is bronchial artery embolisation by interventional radiology — the initial treatment for massive haemoptysis (immediate success 98 percent in the paediatric series; about half need a repeat procedure later). Surgical resection is reserved for localised, refractory bleeding after failed embolisation. [21] [22] [30]

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