Pulmonology & Medical Genetics & Family Medicine
Cystic fibrosis (cystic fibrosis)
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Cystic fibrosis—known by this name in Quebec and Canada, and referred to as mucoviscidosis in Europe—is the most common serious inherited genetic disorder among people of European descent. It is caused by mutations in the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) gene, located on chromosome 7, which encodes a chloride channel present on the surface of epithelial cells in many organs. The defective CFTR protein leads to abnormal transport of chloride and sodium ions across cell membranes, resulting in abnormally thick, viscous, and dehydrated secretions in the lungs, pancreas, bile ducts, intestines, sweat glands, and genital tract. In Quebec, the incidence is approximately 1 in 3,600 births, and it is estimated that more than 4,200 people are living with cystic fibrosis in Canada. The most common mutation, deltaF508 (or F508del), accounts for approximately 70% of mutated alleles in North America—it causes a folding defect in the CFTR protein, which is degraded before reaching the cell membrane. More than 2,000 mutations in the CFTR gene have been identified to date, with clinical consequences that vary widely depending on their functional class. Long considered a fatal pediatric disease affecting young children, cystic fibrosis has undergone an unprecedented therapeutic revolution since the 2010s with the advent of CFTR modulators—particularly elexacaftor-tezacaftor-ivacaftor (Trikafta/Kaftrio) — which directly correct the functional defect in the CFTR protein in the majority of patients, radically altering the course of the disease. Median life expectancy now exceeds 50 years in Canada for patients born today, and continues to rise.
Pathophysiology, diagnosis, and organ damage
- Genetics and CFTR mutation classes: autosomal recessive inheritance — two mutated alleles required to develop the disease — healthy carriers (heterozygotes) represent 1/25 people of European descent; mutation classes according to their functional impact: class I (nonsense mutations — W1282X, G542X): complete absence of CFTR protein synthesis — severe form; class II (processing mutations — F508del: the most frequent): CFTR protein synthesized but misfolded → degraded in the endoplasmic reticulum before reaching the membrane — severe form — target of CFTR correctors (lumacaftor, tezacaftor, elexacaftor); class III (gating mutations — G551D): CFTR protein present at the membrane but channel does not open properly — moderate to severe form — target of CFTR potentiators (ivacaftor); class IV (conduction mutations): channel open but reduced conductance — moderate form; class V (splicing mutations): reduced amount of normal protein — moderate to mild form; class VI: unstable protein at the membrane — variable form
- Pulmonary involvement (main cause of morbidity and mortality): Thick, dehydrated mucus in the bronchi → stasis + obstruction of the small airways → progressive chronic bacterial colonization: Staphylococcus aureus (from childhood onward) → Haemophilus influenzae → Pseudomonas aeruginosa (chronic colonization in 70–80% of adults — a marker of disease progression) → Burkholderia cepacia complex (genovar III = B. cenocepacia — cepacia syndrome — fulminant necrotizing pneumonia — high mortality) + Stenotrophomonas maltophilia + Achromobacter xylosoxidans + nontuberculous mycobacteria (NTM — Mycobacterium abscessus — difficult to treat); excessive neutrophilic inflammation of the bronchi → release of neutrophil elastase + metalloproteases → progressive destruction of the lung parenchyma → diffuse bronchiectasis + chronic respiratory failure; pulmonary complications: acute exacerbations (increased cough + increased purulent sputum production + dyspnea + decreased FEV1 + fever) + hemoptysis (20–30% of adults — sometimes massive) + pneumothorax + allergic bronchopulmonary aspergillosis (ABPA — total IgE + anti-Aspergillus antibodies + infiltrates) + end-stage chronic respiratory failure
- Extrapulmonary manifestations: exocrine pancreas (85–90% of patients): obstruction of the pancreatic ducts → autodigestion → exocrine pancreatic insufficiency → malabsorption of fats and fat-soluble vitamins (A, D, E, K) → steatorrhea + growth and weight failure + vitamin deficiencies → pancreatic enzyme replacement therapy (PERT); endocrine pancreas: cystic fibrosis-related diabetes (CFRD) — affects 40–50% of adults — mixed mechanism (destruction of the islets of Langerhans + peripheral insulin resistance during exacerbations) — distinct from type 1 and type 2 diabetes — preferred treatment: insulin; liver and biliary tract: focal biliary cirrhosis (5–10% of adults with CF) + gallstones + hepatic steatosis; intestine: meconium ileus (10–20% of newborns with CF — first clinical manifestation) + distal intestinal obstruction syndrome (DIOS — formerly meconium equivalent — adults) + chronic constipation + rectal prolapse (children); genitourinary system: obstructive azoospermia due to congenital bilateral absence of the vas deferens (CBAVD — 97–98% of men) → near-constant male infertility (female fertility preserved but reduced); sweat glands: sweat test (sweat chloride ≥60 mmol/L = diagnosis); ENT: nasal polyposis (50% of adults) + chronic sinusitis + sensorineural hearing loss (aminoglycosides)
- Diagnosis : Universal newborn screening in Quebec since 2019: measurement of immunoreactive trypsin (IRT) on a blood blot (Day 3) → if IRT is elevated → CFTR genetic testing + confirmatory sweat test; sweat test (Gibson-Cooke method): pilocarpine iontophoresis + measurement of sudoral chloride — chloride ≥60 mmol/L = confirmed CF diagnosis; chloride 30–59 mmol/L = borderline result (CFTR-RD — related disorder); chloride <30 mmol/L = normal; extended genetic analysis (CFTR mutation panel): confirms the diagnosis + identifies mutations to guide targeted therapy (eligibility for modulators); spirometry: FEV1 (forced expiratory volume in one second) — key prognostic marker — FEV1 <40% predicted = indicator of advanced severity + evaluation for transplantation; High-resolution chest CT: extent of bronchiectasis + bronchial wall thickening + mucoid impaction + consolidation
Treatment
| Treatment | Mechanism, molecules, and modalities | Effectiveness, results, and precautions |
|---|---|---|
| CFTR protein modulators Therapeutic Revolution — Treatment of the Molecular Cause |
CFTR modulators are small molecules that directly target the functional defect in the CFTR protein—they do not correct the DNA mutation but partially or fully restore the protein’s function; two main classes: correctors (correct the folding and intracellular trafficking of the CFTR protein, class II—e.g., lumacaftor, tezacaftor, elexacaftor) + potentiators (increase the opening time of the CFTR channel at the membrane—e.g., ivacaftor); ivacaftor (Kalydeco)—potentiator alone: gating mutations (G551D and 8 other responsive mutations) — FEV1 +10.6 L/s vs. placebo (STRIVE 2011 NEJM) — sudoral chloride −48 mmol/L — Health Canada approval 2012 — 4–5 L/s in eligible patients; lumacaftor-ivacaftor (Orkambi): first-generation corrector + potentiator — F508del homozygotes — FEV1 +2.6 to +4 L/s — modest improvement — pulmonary side effects (initial bronchospasm) + drug interactions (CYP3A4) — largely replaced by Trikafta; tezacaftor-ivacaftor (Symdeko/Symkevi): second-generation corrector + potentiator — FEV1 +4% — better tolerated than Orkambi; elexacaftor-tezacaftor-ivacaftor (Trikafta/Kaftrio): triple combination — next-generation corrector (elexacaftor) + second-generation corrector (tezacaftor) + potentiator (ivacaftor) — dosage: 2 tablets in the morning + 1 tablet in the evening — eligibility: ≥1 F508del copy + any responsive mutation — covers >90% of patients with CF in Canada | Trikafta — clinical results (VX19-445-102 trial, Middleton 2019 NEJM): FEV1 +14.3 L/s at 24 weeks vs. placebo + sudoral chloride −41.8 mmol/L + quality-of-life score (CFQ-R respiratory) +20 points + 63% reduction in pulmonary exacerbations at 24 weeks + BMI +1.0 kg/m²; long-term follow-up (AURORA Registry, Cystic Fibrosis Foundation Registry): sustained improvement at 2–3 years + reduced lung transplant rate + improved survival; Trikafta reimbursement in Canada: approved by Health Canada in June 2021 (≥12 years) then extended to ≥6 years (2022) and ≥2 years (2023) — reimbursed in Quebec (RAMQ) since November 2021 for patients ≥12 years old (F508del homozygotes or heterozygotes + responsive mutation) — exceptional access application process for other genotypes; Trikafta side effects: elevated transaminases (10–15 % — monthly liver monitoring for the first 3 months) + lens opacities (cataracts — ophthalmological screening before treatment in those <18 years) + CYP3A4 interaction (rifampicin, azithromycin — dose adjustment) + skin rash; Trikafta cost: approximately 350,000 CAD/year without reimbursement — RAMQ reimbursement radically changes accessibility in Quebec |
| Respiratory physiotherapy and mucociliary clearance Pillar of treatment — daily for life |
Respiratory physical therapy (RPT) is a fundamental and irreplaceable treatment for cystic fibrosis—its goal is to mobilize and clear thick bronchial secretions that obstruct the airways and serve as a substrate for chronic bacterial colonization; airway clearance techniques (ACT): autogenic drainage (AGD): a technique involving controlled active exhalation at different lung volumes—learned with a physical therapist specializing in CF—the gold standard in Europe and Canada—can be performed independently without equipment; high-frequency oral oscillation (OOFE — Acapella, Flutter): device creating expiratory oscillatory resistance → intrabronchial vibrations → loosening of secretions + improvement in mucociliary clearance; Positive expiratory pressure (PEP): mask or mouthpiece providing resistance to exhalation → recruitment of collateral alveoli → mobilization of secretions from the small airways; high-frequency chest oscillation vest (ThAIRapy vest): used primarily in North America + in young children or uncooperative patients; frequency: 1–2 sessions/day of 20–40 min — increased during exacerbations (3–4 sessions/day); mucoclearance-facilitating medications inhaled prior to PTR: hypertonic saline solution (3–7 M NaCl — 4 mL nebulized) → rehydration of the bronchial mucosal surface → improvement in viscosity; inhaled mannitol (Bronchitol): inhaled osmotic agent — approved by Health Canada in 2021 | PTR should ideally be taught and supervised by a physical therapist specializing in cystic fibrosis at an accredited CF center—in Quebec, adult and pediatric CF centers (CHU Sainte-Justine, CHUM, Hôpital Maisonneuve-Rosemont, CHU de Québec—IUCPQ) have multidisciplinary teams that include experienced physical therapists; rhDNase (dornase alfa — Pulmozyme): mucolytic enzyme — cleaves extracellular DNA released by necrotic polymorphonuclear cells in bronchial secretions → reduces mucus viscosity — administered via nebulizer prior to PTR (2.5 mg × 1/day) — reduction in exacerbations of 29% and improvement in FEV1 of 5.8% (Fuchs 1994 NEJM) — covered by RAMQ; since the introduction of Trikafta, secretion volume and viscosity have decreased significantly within 4 to 8 weeks of initiation — adjust the duration and intensity of PTR based on clinical response (but maintaining a daily routine is recommended) |
| Antibiotic therapy - infections and exacerbations Maintenance and Exacerbation Strategies |
Antibiotic therapy in cystic fibrosis—three distinct strategies depending on the goal: early eradication of Pseudomonas aeruginosa (primary colonization detected by sputum culture): inhaled tobramycin (TOBI) 300 mg twice daily for 28 days + oral ciprofloxacin 750 mg twice daily for 4 weeks — eradication rate 75–85% % — objective: to delay chronic colonization; long-term anti-Pseudomonas antibiotic therapy (established chronic colonization): alternating inhaled tobramycin (TOBI — 1 month ON / 1 month OFF) OR inhaled aztreonam (Cayston) — maintenance of pulmonary stability + reduction in exacerbations + slowing of FEV1 decline; oral azithromycin 250–500 mg × 3/week: anti-inflammatory + immunomodulatory effect (non-antibiotic) — reduces exacerbations by 35–40% in patients colonized with P. aeruginosa — precaution: do not use if active nontuberculous mycobacteria (masks and promotes resistance); treatment of acute pulmonary exacerbations: hospitalization criteria — FEV₁ drop >10% + significant increase in secretions + hemoptysis + SpO₂ <95% + patient unable to maintain outpatient care; IV antibiotics: based on antibiotic susceptibility testing (recent sputum cultures required) — P. aeruginosa: piperacillin-tazobactam 4.5 g × 4/day IV + tobramycin IV (once daily — 10–12 mg/kg/day — pharmacokinetic monitoring required — nephrotoxicity + ototoxicity) — duration: 14–21 days IV or until return to baseline FEV1 | Managing bacterial resistance is a major challenge in cystic fibrosis—patients are exposed to dozens of courses of antibiotics over the course of their lives → emergence of multidrug-resistant (MDR) P. aeruginosa + B. cepacia complex + nontuberculous mycobacteria (M. abscessus—complex treatment: IV amikacin + imipenem + cefoxitin ± azithromycin × 12 months); segregation of patients in hospitals and clinics: patients colonized with B. cepacia complex (particularly B. cenocepacia) must never come into contact with other CF patients — single rooms mandatory — risk of interpatient transmission and fulminant cepacia syndrome + relative contraindication for lung transplantation (B. cenocepacia — very high post-transplant mortality) ; ototoxicity of aminoglycosides (tobramycin): annual audiometric screening in patients receiving inhaled or IV tobramycin — nephrotoxicity: creatinine + clearance before each IV course + peak and trough pharmacokinetic measurements; Trikafta significantly reduces the frequency of exacerbations requiring IV antibiotics (63% reduction in % trials) → decreased cumulative exposure to aminoglycosides → reduced risk of ototoxicity |
| Nutritional and pancreatic support PERT — pancreatic enzymes — fat-soluble vitamins |
Exocrine pancreatic insufficiency (85–90% of patients): pancreatic enzyme replacement therapy (PERT): Creon (pancreatin—lipase + amylase + protease in the form of enteric-coated, gastro-resistant microspheres)—take at the start of a meal or snack—dosage: 500–2,500 IU lipase/kg/meal (max 10,000 IU lipase/kg/day) — titrate based on steatorrhea and weight gain; nutritional goals in FK: target BMI ≥22 kg/m² (women) and ≥23 kg/m² (men) — 1–3 times the expected weight ≥90% of the recommended intake in children; high-calorie, high-fat diet (caloric intake 110–200% of recommended intake) — no fat restriction (unlike standard pancreatitis); mandatory fat-soluble vitamin supplementation: vitamin A (10,000 IU/day) + vitamin D (800–2,000 IU/day — annual 25-OH-D measurement — target 75–120 nmol/L) + vitamin E (100–400 IU/day) + vitamin K (coagulopathy prevention — 1–10 mg/day); additional salt in summer or during intense exercise (excessive NaCl loss in sweat); nocturnal enteral nutrition via nasogastric tube or gastrostomy: if BMI <18 or weight <85 kg despite optimal oral management — often prescribed for adolescents during growth spurts; CF-related diabetes (CRD): rapid-acting insulin therapy at meals + nocturnal basal insulin if fasting hyperglycemia — avoid oral antidiabetics (except metformin as a second-line treatment) — specialized endocrinological follow-up; osteoporosis: bone densitometry starting at age 18 + bisphosphonates if T-score <−2.5 | Nutrition is a major independent prognostic factor in CF — nutritional status is directly correlated with lung function and survival (BMI <18 associated with accelerated FEV1 decline and increased mortality); since Trikafta: significant improvement in nutritional status in the first months of treatment (increase in body weight + improved fat absorption) — possible reduction in PERT doses needed in some patients (adjustment guided by clinical steatorrhea and nutritional status, not empiric cessation); CF-related diabetes (CFRD) is often asymptomatic initially — annual screening with oral glucose tolerance test (OGTT 75g — 2h) recommended from age 10 in all patients — screening with HbA1c is insufficient in CF (accelerated erythrocyte turnover + anemia) — use postprandial glycemia; liver transplantation: indicated in decompensated cirrhosis (Child-Pugh C) — can be performed in combination with lung transplantation in some patients |
| Lung transplantation End-stage — FEV1 <30% of predicted or rapid decline |
Bilateral lung transplantation (double-lung transplant) is the last-resort treatment for end-stage respiratory failure associated with cystic fibrosis—CF is the third most common indication for lung transplantation worldwide (after COPD and idiopathic pulmonary fibrosis); Transplantation criteria (Cystic Fibrosis Foundation + ISHLT): FEV1 <30% of predicted (or decline >20% of predicted value within 12 months) + resting SpO₂ <90% on oxygen or during exercise + hypercapnia (PaCO₂ >50 mmHg) + frequent exacerbations requiring hospitalization + severe treatment-resistant malnutrition + PAH + recurrent massive hemoptysis; relative or absolute contraindications: colonization with B. cenocepacia (genotype IIIA — post-transplant mortality of 50–75% at 1 year — contraindication in most centers, including the IUCPQ) + active, uncontrolled M. abscessus + severe obesity (BMI >35) + severe uncorrectable renal or hepatic insufficiency + documented non-adherence to therapy + major comorbidities; lung transplantation program in Quebec: IUCPQ (Quebec University Institute of Cardiology and Pulmonology) — the only lung transplantation center in Quebec + pre-transplant follow-up centers (CHUM, CHU Sainte-Justine); post-transplant survival FK: 80 % at 1 year / 55–60 % at 5 years / 40–45 % at 10 years (ISHLT registry 2022) — better outcomes in FK patients than for other indications (younger population + fewer comorbidities); complications: chronic rejection (CLAD—bronchiolitis obliterans) + opportunistic infections (bacterial, viral [CMV], fungal) + immunosuppressant toxicity | Since the introduction of Trikafta, the number of CF patients on transplant waiting lists has decreased significantly in countries where Trikafta is covered—some patients awaiting transplantation have even been removed from the list after starting Trikafta due to the clinical improvement achieved; however, Trikafta does not reverse irreversible lung damage that has already occurred (bronchiectasis, parenchymal destruction)—patients with very low FEV1 (<30–40% of predicted) may have a partial response and remain candidates for transplantation even while on Trikafta; Management of CF medications post-transplant: CFTR modulators (Trikafta) are generally continued after transplantation—they continue to benefit non-transplanted organs (pancreas, sinuses, intestines, genital tract) — interactions with immunosuppressants (tacrolimus + cyclosporine — CYP3A4 substrates) require adjustment of immunosuppressant doses (a 50% reduction in tacrolimus is recommended upon initiation of Trikafta) + monitoring of residual levels; palliative care: for patients ineligible for transplantation or in the terminal phase — specialized palliative care program + cystic fibrosis team + ambulatory oxygen therapy + non-invasive ventilation + advance discussion of care directives |
ℹ️
Trikafta and access in Quebec — an accessible revolution: Elexacaftor-tezacaftor-ivacaftor (Trikafta) has been reimbursed by the RAMQ in Quebec since November 2021 for patients aged 12 and over with at least one F508del mutation, and since 2023 for children aged 2 and over according to Canadian guidelines. For eligible patients with other non-F508del mutations, an exceptional access request (exception drug) is possible through the RAMQ upon recommendation from a CF-specialized pulmonologist. Cystic Fibrosis Canada (cysticfibrosis.ca) offers access support resources and a patient assistance program. Quebec patients whose genotype is not covered by Trikafta are followed in compassionate access programs or ongoing clinical trials for new modulator combinations (vanzacaftor-tezacaftor-deutivacaftor – VX-522 – in phase 3).
Emergency — Severe exacerbation and massive hemoptysis
Dial 911 or go immediately to the emergency room if : Sudden shortness of breath + SpO₂ <90% % + rapid decline in respiratory function Severe pulmonary exacerbation - IV antibiotics + intensive inpatient PTR.
Massive hemoptysis (>240 mL/24h or massive hemoptysis) Call 911. Affected lateral position. No anticoagulants. Emergency bronchial artery embolization at a specialized center.
Sudden chest pain + sudden shortness of breath + unilateral absence of breath sounds → pneumothorax — surgical emergency → chest drain.
Consult at Clinique Omicron
Les médecins de Clinique Omicron assurent le suivi de première ligne des patients atteints de fibrose kystique en collaboration avec les centres spécialisés FK au Québec : gestion des infections intercurrentes, renouvellement des ordonnances, suivi nutritionnel, dépistage du diabète lié à la FK et coordination des demandes de remboursement des modulateurs CFTR (RAMQ). Des consultations sont disponibles dans nos points de service au Québec et via la télémédecine. Pour prendre rendez-vous, choisissez votre service en ligne.
The content of this page is provided for informational purposes only and does not substitute for the advice of a qualified healthcare professional specializing in cystic fibrosis. Optimal management of cystic fibrosis requires a multidisciplinary team at an accredited center—pulmonologist, physical therapist, nutritionist, specialized nurse, and social worker.
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