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Cystic Fibrosis

Cystic fibrosis is an autosomal recessive multi-system condition caused by a mutation in the CFTR gene, which primarily affects the lungs, but also affects the liver, kidneys, and intestines. This CFTR mutation leads to increased sodium absorption and abnormal chloride secretion across the airway epithelial cells. This causes thicker mucus production, which impairs ciliary function. The 3 key consequences here are:

  • Thick pancreatic and biliary secretions - Cause blockage of ducts, therefore a lack of digestive enzymes in the gut

  • Thick, sticky airway secretions - Reduced airway clearance, leading to increased susceptibility to chest infections

  • Congenital bilateral absence of vas deferens - Causes infertility

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An airway with cystic fibrosis - National Heart Lung and Blood Institute

Presentation

In neonates, it presents with Meconium Ileus, which is where the meconium gets thick and sticky, leading to bowel obstruction. Should be suspected if not passing meconium within 24 hours, abdominal distention, and vomiting.


In later childhood, they'll present with:

  • Chronic productive cough

  • Recurrent chest infections

  • Failure to thrive

  • Pancreatic insufficiency

    • Diabetes meillitus due to endocrine loss

    • Steatorrhoea due to exocrine loss

  • Abdominal pain, Bloating

  • Very salty sweat


Diagnosis and Investigations

Diagnostic investigations include:

  • Neonatal heel prick day between day 5 and day 9

  • Sweat test - chloride > 60 mmol/L makes CF likely

  • Genetic screening for CFTR mutation

  • Faecal elastase - tests pancreatic exocrine function


Other investigations are done in those with known CF to look for the causes of symptoms, as well as for other complications, and to assess disease progression. This may include:

  • Sputum culture

  • Bloods - FBC, U&Es, LFTs, Clotting, Vitamin levels (may lack fat-soluble vitamins ADEK)

  • Glucose - tests pancreatic endocrine function

  • Spirometry - obstructive pattern

  • Abdominal US/XR

  • CXR - hyperinflation, bronchiectasis


Management

Conservative - Chest physio, Dietician


Medical - This includes:

  • Infective exacerbations - Abx, Nebulised mucolytics (Dornase alfa), Bronchodilators

  • Pancreatic insufficiency - Insulin, CREON, Vitamins ADEK

  • Abnormal liver function - Ursodeoxycholic acid (naturally-occurring bile acid that prevents liver disease in those with CF)

  • Worsening lung disease - Oxygen, NIV, Diuretics if signs of cor pulmonale


N.B. Prophylactic Flucloxacillin may be given for those with reccurent chest infections.




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