Cystic Fibrosis

Question 1

Give a quick summary of cystic fibrosis.

Answer 1

• genetic disorder (monogenic)
• defect of a chloride ion channel in exocrine cells
• there is abnormal secretion of fluid in GIT, respiratory tract and the reproductive tract

Question 2

What causes cystic fibrosis?

Answer 2

• a genetic defect of the cystic fibrosis transmembrane regulator (CFTR) gene on chromosome 7
• autosomal recessive

Question 3

What is the pathology of cystic fibrosis?

Answer 3

• CFTR forms chloride ion channels on epithelial cells
• a mutation makes the cells impermeable to chloride, leads to impaired chloride ion transport across the cell membrane
• this causes abnormal secretion:
• – the chloride ions move from blood vessels into goblet cells
• – the chloride ions accumulate in the cell, increasing the concentration and drawing water and sodium back in
• – result is viscous, sticky mucous

in the repsiratory tract the mucus:

1) obstructs air flow when it plugs the airways, and decreases function
2) is hard to clear via cilia and results in recurrent infections

Question 4

How is CF diagnosed?

Answer 4

• sweat test (individuals with CF have 2-5 times the amount of sodium and chloride in their sweat)
• CF in a sibling
• newborn screen (measure blood levels of trypsinogen, since they will be elevated due to obstruction in pancreatic ducts)
• GI and respiratory manifestations

Question 5

How is CF treated?

Answer 5

• no cure
• try to improve QOL
• DNAase (because tissue damaged by inflammation release their contents, including DNA, and the strands make mucus stickier)
• control infections (treat, prophylaxis, gamma globulins)
• diet modification (smaller meals, low fat and high calorie)
• pancreatic enzyme supplementation
• anti-inflammatory drugs