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Flashcards in Cystic Fibrosis Deck (11):

What is the genetic abnormality in CF?

- CFTR (cystic fibrosis transmembrane conductance regulator) abnormality
- Autosomal recessive (homo/heterozygous)


What is CFTR, and what is its physiological role?

• chloride channel found in the apical membrane of epithelial cells - lungs, intestines, pancreatic ducts, sweat glands, and reproductive organs
• CFTR has two functions:
1. Inhibits ENaC -> dec sodium abs into cell -> water doesn't follow into cell
2. Secretes Cl- -> reduces water absorption


In CF, what does the CFTR not do?

• -> ENaC not inhibited and Cl- ions not secreted
• abnormal salt transport by epithelial cells -> thick, sticky secretions


Complications of CF

○ Pancreas: blockage ducts -> early activation of pancreatic enzymes -> autodestruction

○ Intestine: bulky stools -> obstruction (esp. ileum)

○ Respiratory: cycle of mucus retention -> chronic infection and inflammation -> chronic pulmonary disease inc. cor pulmonale -> resp failure

• Cor pulmonale 
• DM (onset usually between 18-21 years of age) 
• Osteoporosis 
• Chronic sinusitis 
• Failure to thrive 
• Advanced liver disease 


How does CF lead to chronic lung infections?

1. thick mucous -> obstruction -> infection -> inflammation -> thickened mucous

2. ASL (airway surface liquid) volume hyperabsorption has important consequences for both the PC (periciliary) and the mucus layer:
□ Volume depletion of PCL →failure of ciliary beating
□ Absence of lubrication → adherent mucus plaque

-> promotes chronic infection


What might be one of the first symptoms of CF?

Failure to pass meconium


What features might CF present with?

• Bowel obstruction with meconium (meconium ileus) 
• Failure to thrive 
• Insatiable appetite 
• Wet cough 
• Recurrent infection 
• Chronic sinusitis 
• Haemoptysis 
• Steatorrhoea 
• Pancreatitis 
• Hepatosplenomegaly (rare) 
• Genital abnormalities in males (bilateral absence of vas deferens) 


Ix for CF

(Newborn screening = immunoreactive trypsinogen test)

1. Chloride sweat test: positive (> 60 mmol/L) in homozygote: Dx confirmed

2. If <60mmol/L (but clinically suspect) -> genetic testing:
□ 2 mutations = Dx

3. If 1 mutation - further tests:
□ panc enczymes in faeces
□ sinus radiography
□ sputum/throat swaps
□ PFTs, CXR (hyperinflated, increased pulmonary markings (especially in upper lobes))


Classic presentation of CF

Infant with FTT


Most common lung infection in CF



Mx of CF

- General: chest physio, postural drainage
- Nutrition: high energy + protein diet, fat-soluble vit supp

• Bronchodilators (salbutamol +/- ipratropium bromide) 
• Inhaled mucolytic (dornase alfa and hypertonic saline) 
• IV Abx for exacerbations (tobramycin and ticarcillin/clavulanic acid)  
• Pancreatic enzyme replacement, bile acids for liver disease