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Cystic fibrosis

Background knowledge 🧠

Definition

  • A multisystem genetic disorder affecting the lungs, pancreas, liver, and intestines, characterised by production of thick, sticky mucus

Pathophysiology

  • Defective CFTR protein leads to impaired chloride transport across epithelial cells.
  • Results in thick, viscous secretions in respiratory, gastrointestinal, and reproductive tracts

Aetiology

  • Autosomal recessive inheritance of mutations in the CFTR gene on chromosome 7

Clinical Features 🌑️

Symptoms

  • Respiratory: Recurrent chest infections, wheeze, cough, dyspnoea, and sputum production.
  • GI: Meconium ileus in neonates, pancreatic insufficiency, malabsorption, and steatorrhoea
  • Failure to thrive and malnutrition
  • Male infertility due to absent vas deferens
  • CF-related diabetes
  • Salty sweat

Signs

  • Cyanosis
  • Clubbing
  • Bilateral coarse crepitations

Investigations πŸ§ͺ

Tests

  • Sweat test: elevated chloride concentration is diagnostic
  • Genetic testing for CFTR mutations
  • Chest X-ray: bronchiectasis, atelectasis, and infiltrates
  • Pulmonary function tests: obstructive pattern
  • Stool elastase: to assess pancreatic function

Management πŸ₯Ό

Management

  • Airway clearance techniques: physiotherapy, positive expiratory pressure devices
  • Inhaled bronchodilators
  • Mucolytics, e.g. rhDNase (dornase alfa; recombinant human deoxyribonuclease)
  • Antibiotic therapy for respiratory infections (e.g., Pseudomonas aeruginosa)
  • Oral pancreatic enzyme replacement to aid digestion
  • High-calorie diet with vitamin supplementation
  • CFTR modulator therapies for specific mutations
  • Lung transplantation in advanced disease

CFTR modulator therapies

  • CFTR modulators are available depending on the CFTR mutation
  • They bind to the defective CFTR protein and increase the protein’s functionality
  • More efficacious when started in younger patients, conferring better prognosis
  • Example: Ivacaftor

Complications

  • Chronic respiratory failure
  • Cor pulmonale
  • Diabetes mellitus
  • Liver cirrhosis and portal hypertension
  • Distal intestinal obstruction syndrome
  • Complex/multi-drug-resistant infections, e.g. Burkholderia cepacia, MDR Pseudomonas, non-tuberculous mycobacteria, Aspergillus

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