Cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disorder in which there is a mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) causing thick, sticky secreations

70% of cases are due to a deletion at ΔF5O8 on chromosome 7. 
Incidence is 1 in 2500. 

Presentation may be: 
  • Finding at newborn screening 
    • Guthrie blood spot test, looking for raised levels of trypsinogen
  • Meconium ileus (10%)
  • Failure to thrive due to pancreatic insufficiency and malabsorption 
    • Steatorrhoea 
    • Diarrhoea 
    • Abdominal distension
  • Recurrent respiratory infections 

  • Diagnosis is confirmed by the pilocarpine sweat test 
    • >60mmol/l Na/Cl diagnostic, <40mmol/l Na/Cl normal 
  • PCR can pick up >90% of mutations 
  • Faecal elastase is a sensitive and specific test to detect decreased exocrine pancreatic function
  • Spirometry can be used to monitor disease progress – it shows an obstructive pattern 

Features/complications of CF include:
  • Chronic pulmonary infection and inflammation 
  • Bronchiectasis 
  • Haemoptysis 
  • Pneumothorax 
  • Pancreatic insufficiency  and malabsorption
  • Liver disease 
  • Chronic sinusitis 
  • Diabetes (a third of patients by age 30)
  • Male infertility (congenital absence of vas deferens) 
  • Osteoporosis 
  • Meconium ileus 
  • Distal intestinal obstruction syndrome 
  • Rectal prolapse 
  • Nephrolithiasis 
  • Finger clubbing 

Organisms which cause infections in CF include: 
  • Pseudomonas 
  • Burkholderia cepacia 

  • Enzyme replacement 
  • Physio to clear airways 
  • Prompt treatment of infection 
  • ?heart/lung transplant 

Death currently around aged 30 but expected to rise to around 50. 

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