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Cystic fibrosis (CF)

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Cystic fibrosis (CF)

Cystic fibrosis (CF) is an inherited multisystem disease caused by abnormal chloride transport, resulting in thick, sticky secretions, especially in the lungs and digestive system.

Also called

Mucoviscidosis (older term)

ICD-10

E84.9

Specialty

Pulmonology

Onset

Chronic

Reviewed

July 2026

On This Page

Overview

Cystic fibrosis mainly affects the:

  • Lungs
  • Pancreas
  • Gastrointestinal tract
  • Sinuses
  • Reproductive system
  • Sweat glands

Abnormally thick mucus causes airway obstruction, recurrent lung infections, and progressive lung damage.

Etiology & Risk Factors

Cause:

Cystic fibrosis is caused by mutations in the CFTR gene.

Inheritance

  • Autosomal recessive
  • Both parents usually carry one abnormal CFTR gene

Common Mutation

  • F508del is the most common CFTR mutation.

Risk Factors

  • Family history of cystic fibrosis
  • Sibling with cystic fibrosis
  • Parents who are CFTR mutation carriers

Pathophysiology

Flow Chart:

CFTR gene mutation
⬇
Abnormal chloride and bicarbonate transport
⬇
Reduced water movement into secretions
⬇
Thick, dehydrated mucus
⬇
Impaired mucus clearance
⬇
Airway obstruction + Bacterial infection
⬇
Chronic inflammation
⬇
Bronchiectasis and progressive lung damage

Other Organs

Thick pancreatic secretions
→ Duct obstruction
→ Pancreatic insufficiency
→ Malabsorption

Abnormal sweat gland function
→ Increased salt loss in sweat

Clinical Presentation

  1. Respiratory Features

    • Chronic cough
    • Persistent sputum production
    • Recurrent chest infections
    • Wheezing
    • Dyspnea
    • Bronchiectasis
    • Hemoptysis

    Gastrointestinal Features

    • Poor weight gain
    • Malabsorption
    • Steatorrhea
    • Abdominal symptoms
    • Pancreatic insufficiency

    Other Features

    • Salty-tasting skin
    • Chronic sinusitis
    • Nasal polyps
    • Digital clubbing
    • Male infertility

    In Newborns

    • Meconium ileus
    • Failure to thrive

History Taking

    • Chronic cough?
    • Daily sputum?
    • Recurrent chest infections?
    • Wheezing or dyspnea?
    • Previous bronchiectasis?
    • Poor weight gain?
    • Greasy or bulky stools?
    • Abdominal symptoms?
    • Chronic sinus problems?
    • Nasal polyps?
    • Salty-tasting skin?

Physical Examination

  • Look for:

    • Low body weight
    • Poor growth
    • Digital clubbing
    • Cyanosis in advanced disease
    • Respiratory distress

    Chest Examination

    • Coarse crackles
    • Wheezing
    • Reduced air entry in advanced disease

    Other Findings

    • Nasal polyps
    • Signs of malnutrition
    • Abdominal distension
    • Signs of chronic liver disease in advanced cases

Investigations

  • Sweat Chloride Test — Key Test

    Measures the chloride concentration in sweat.

    An elevated sweat chloride level supports the diagnosis.

    CFTR Genetic Testing

    Used to:

    • Identify CFTR mutations
    • Confirm the diagnosis
    • Determine eligibility for CFTR modulator therapy

    Newborn Screening

    May detect cystic fibrosis before symptoms develop.

    Respiratory Tests

    • Sputum culture
    • Pulmonary function tests
    • Chest X-ray
    • CT chest

    Other Tests

    • Pancreatic function testing
    • Nutritional assessment
    • Blood glucose monitoring
    • Liver function tests

Diagnosis

  • Diagnosis is based on:

    1. Clinical Features or Positive Newborn Screening

    Together with:

    2. Evidence of CFTR Dysfunction

    Demonstrated by:

    • Abnormal sweat chloride testing
    • CF-causing CFTR mutations
    • Specialized CFTR functional testing when needed

    Important Note

    The sweat chloride test is the main diagnostic test for cystic fibrosis.

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Related Topics

Management

Cystic Fibrosis · Treatment

TREATMENT IS MULTIDISCIPLINARY, LIFELONG, AND INCREASINGLY DISEASE-MODIFYING CF is caused by mutations in the CFTR gene → defective chloride channel → thick secretions, recurrent infection, progressive organ damage. Management addresses the underlying CFTR defect (modulators), airway clearance, infection control, nutritional support, and complication prevention.
Core Treatment Pillars
1
CFTR Modulator Therapy
Disease-modifying drugs targeting the underlying CFTR defect — correct protein folding/function, not just symptoms. Transformative when applicable.
Mutation-specific
2
Airway Clearance
Daily physiotherapy techniques (ACBT, PEP, HFCWO) combined with mucolytics to clear thick secretions and reduce infective burden.
Daily — lifelong
3
Infection Management
Prophylactic, suppressive and acute antibiotic therapy targeting chronic colonising organisms (esp. Pseudomonas aeruginosa, Staphylococcus aureus, Burkholderia).
Chronic + acute
4
Nutritional & Systemic Support
Pancreatic enzyme replacement, fat-soluble vitamin supplementation, high-calorie diet, CFRD management, and multiorgan complication screening.
Lifelong
Treatment Category Drug / Intervention Notes
CFTR Modulator — Triple Combination Elexacaftor / Tezacaftor / Ivacaftor (ETI, Kaftrio/Trikafta) For F508del (at least one copy, ~90% of patients). Most effective modulator available — dramatic improvement in FEV1, quality of life, and exacerbation rate. Now first-line where eligible.
CFTR Modulator — Potentiator Ivacaftor (Kalydeco) For gating mutations (G551D and others). Opens dysfunctional CFTR channels. Not effective for F508del alone.
CFTR Modulator — Dual Lumacaftor / Ivacaftor (Orkambi) or Tezacaftor / Ivacaftor (Symkevi) For homozygous F508del if ETI not yet available or tolerated. Less effective than ETI.
Mucociliary Clearance Dornase alfa (DNase) inhaled daily — Hypertonic saline 7% inhaled Dornase alfa cleaves extracellular DNA, reducing sputum viscosity. Hypertonic saline hydrates airway surface. Use bronchodilator first, then mucolytic, then physiotherapy.
Chronic Antibiotic Suppression Inhaled tobramycin alternating months — Inhaled aztreonam — Oral azithromycin (3x/week) Targets chronic Pseudomonas colonisation. Azithromycin has anti-inflammatory properties independent of antimicrobial effect. Alternate-month inhaled regimens reduce resistance.
Acute Pulmonary Exacerbation IV antipseudomonal antibiotics (e.g. piperacillin-tazobactam + tobramycin or meropenem) Based on most recent sputum sensitivities. IV for moderate-severe exacerbations; oral for mild. Minimum 14-day course. Intensify airway clearance throughout.
Pancreatic Enzyme Replacement Creon (pancrelipase) with every meal and snack 85% of CF patients have exocrine pancreatic insufficiency. Titrated by stool consistency and fat malabsorption symptoms. Essential for caloric absorption.
Vitamin Supplementation Fat-soluble vitamins A, D, E, K daily Malabsorbed due to pancreatic insufficiency and bile salt abnormalities. Especially important for bone health (vitamin D/K) and infection risk (vitamin A/E).
CF-Related Diabetes (CFRD) Insulin (preferred over oral agents) CFRD affects ~50% of adults. Unique — combined insulin deficiency + resistance. Insulin anabolism also helps maintain weight. Annual OGTT screening from age 10.
Bronchodilators Inhaled SABA (salbutamol) before airway clearance Used to pre-treat before physiotherapy/inhaled therapies; improves tolerance and delivery of subsequent treatments.
Lung Transplantation Bilateral lung transplant Definitive treatment for end-stage CF lung disease. Consider referral when FEV1 <30% predicted or rapid decline. Does not cure systemic CF manifestations.
Complications to Monitor
CF-related diabetes (CFRD) — annual OGTT from age 10; insulin is treatment of choice
CF-related bone disease — DEXA scanning; vitamin D + bisphosphonates if indicated
CF liver disease — cirrhosis/portal hypertension in ~10%; ursodeoxycholic acid; consider transplant
Haemoptysis — minor is common; massive haemoptysis requires bronchial artery embolisation
Pneumothorax — increased risk; treat as standard but avoid vigorous physiotherapy acutely
Infertility — males almost universally infertile (CBAVD); females reduced fertility; offer counselling
Routine Monitoring
Spirometry — every clinic visit; FEV1 is primary marker of disease progression
Sputum MC&S — every clinic visit; guides antibiotic selection for exacerbations
Weight/BMI/nutritional assessment — every visit; target BMI ≥22 (female) or ≥23 (male)
Annual OGTT — from age 10 for CFRD screening
Annual blood tests — LFTs, vitamin levels (A/D/E), HbA1c, renal function (if aminoglycosides used)
DEXA scan — every 2–5 years from adulthood; more frequent if bone disease present

Complications

  • Bronchiectasis
  • Recurrent pulmonary infections
  • Respiratory failure
  • Hemoptysis
  • Pneumothorax
  • Pancreatic insufficiency
  • Malnutrition
  • Cystic fibrosis-related diabetes
  • Liver disease
  • Osteoporosis
  • Infertility
  • Death

Prognosis

  • Cystic fibrosis is a chronic progressive disease, but survival has improved greatly with modern treatment.
  • Prognosis depends mainly on:
    • Severity of lung disease
    • CFTR mutation
    • Frequency of pulmonary exacerbations
    • Nutritional status
    • Presence of complications
  • Early diagnosis and specialized multidisciplinary care improve outcomes.
  • CFTR modulator therapy has significantly improved outcomes for many eligible patients.

Key Points / Clinical Pearls

  • Cystic fibrosis is an autosomal recessive disease caused by CFTR mutations.
  • Thick secretions affect multiple organs, especially the lungs and pancreas.
  • Chronic cough and recurrent respiratory infections are common.
  • Pancreatic insufficiency causes malabsorption and poor growth.
  • The sweat chloride test is the key diagnostic test.
  • Respiratory cultures guide antibiotic therapy.
  • Airway clearance is a cornerstone of treatment.
  • Pancreatic enzymes and nutritional support are essential in pancreatic insufficiency.