Cystic Fibrosis

Background/Epidemiology

  • Most common fatal genetic disease in caucasians
  • Incidence of ~1 in 2500 live births
  • NB It can be associated with atopy/asthma in up to 88%

Genetics and Pathophysiology

  • Result of mutations (most commonly ΔF508) affecting a gene on chromosome 7 encoding a subunit of a chloride channel (cystic fibrosis transmembrane conductance regulator- CFTR)
    • Results in increased sodium and chloride (salt) in sweat and increased resorption of sodium and water from respiratory epithelium.
    • The main pathology seen in CF is a relative dehydration of the airways which can predispose to bacterial infections and ciliary dysfunction
    • There are other organs affected
      • e.g. pancreas, GI tract and reproductive system
  • Most patients are identified through screening either antenatally (at risk) or at birth (screening)

Diagnosis

  • The majority will be diagnosed by immunoreactive trypsinogen (IRT) on the blood spot (Guthrie) test 6 days post-natally

Complications/Clinical Features

  • Most patients will develop bronchiectasis during childhood.
    • Lungs are ‘fragile’
      • Frequent exacerbations of bronchiectasis
      • Spontaneous pneumothorax (20%)
      • Haemoptysis
      • Nasal polyps
      • Respiratory failure
      • Cor pulmonale
      • Lobar collapse
  • Extra-respiratory features include
    • GI
      • Malabsorption (including failure to thrive) and steatorrhoea
      • Biliary cirrhosis and portal hypertension
      • Gallstones
      • Acute pancreatitis
      • Heartburn and peptic ulcers (often secondary to pancreatic failure)
    • Diabetes (25%)
    • Delayed puberty
    • Male infertility
    • Stress incontinence
    • Osteoporosis
    • Arthropathy
    • Cutaneous vasculitis
    • Rectal prolapse (up to 10%)
      • NB ALL children who present with rectal prolapse in the absence of other symptoms should be investigated for CF

Management

  • Patients require intense physiotherapy to help clear secretions from the lungs
  • Regular nebulised tobramycin is used between acute exacerbations to help prevent/suppress chronic pseudomonas infection
  • Patients will usually require intense (and possibly unusual) antibiotic treatments to tackle all infections (initially normal specific antibiotics for infections but later more specialised anti-pseudomonas antibiotics)
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