Wk 29: Cystic fibrosis

Question 1

What is CF?

Answer 1

• Autosomal recessive genetic disorder
• Single gene mutation on c’some 7: F508

Question 2

What is the normal CFTR action?

Answer 2

• CFTR ion channel export chloride ions
• Attracts water = low viscosity of mucus in lung
• CFTR mutation prevents chloride export, tf thick + sticky mucus
• Chloride imbalance = import sodium into cell
• Leads to water import into cells, dehydrating extracellular compartment

Question 3

How is cystic fibrosis diagnosed?

Answer 3

• Newborn: heel prick - measures immunoreactive trypsinogen in blood
• Genetic mutation analysis
• Sweat test: measures conc chloride in sweat

Question 4

What are the pulmonary effects of CF?

Answer 4

• Defective ion transport = impaired mucociliary clearance
• Airway clogged w/ sticky mucus, impairs clearance of staph/h influenza
• Infection cause inflammatory response, activating neutrophils
• Debris accumulation from bacteria + neutrophils difficult to clear
• Protease from neutrophils damage air way
• Lung function compromised

Question 5

What is the initial infecting pathogen of CF?

Answer 5

Staph A:

• Minor: flucox oral
• Severe: IV flucox or IV vancomycin

Question 6

How is MRSA treated?

Answer 6

• Nasal carriage: mupirocin
• Fusidic acid + rifampicin/trimethoprim
• Oral linezolid
• Severe IV teicoplanin/vanco

Question 7

How is haemophilus influenzae treated?

Answer 7

• Amox orally
• Severe chloramphenicol/cefuroxime

Question 8

Which bacteria causes chronic colonisation?

Answer 8

Pseudomonas aeruginosa

Question 9

How is severe exacerbation of p. aeruginosa managed?

Answer 9

• IV tazocin
• IV tobramycin (synergistic w/ b lactams)

Causes nephrotoxicity + ototoxicity

Question 10

Important points: doxycycline

Answer 10

Light sensitivity

Question 11

Important points: ciprofloxacin

Answer 11

• Interacts w/ milk, antacids, iron, zinc
• Tendon rupture
• Induce convulsions

Question 12

What is used longterm in patients w/ declining lung function, declining clinical status + chronic colonisation?

Answer 12

Azithromycin 250-500mg 3x weekly

Question 13

How does physiotherapy help in CF patients?

Answer 13

Airway clearance technique: red obstruction + resistance

Question 14

What are non-pulmonary manifestations of CF?

Answer 14

• Pancreatic insufficiency
• Cystic fibrosis related diabetes
• Liver disease
• Low mineral bone density
• Infertility in men

Question 15

What is used to treat pancreatic insufficiency?

Answer 15

Pancreatic enzyme replacement + fats soluble vitamins (ADEK)

Question 16

Why does CF cause liver disease?

Answer 16

• CFTR expressed on apical surface of cholangiocytes + biliary epithelium
• Regulates fluid + electrolyte content of bile
• Disrupted function = biliary cirrhosis

Question 17

What are the complications of CF on the liver?

Answer 17

• Portal hypertension
• Esophageal varices
• Ascites
• Hepatic failure

Question 18

What are the risk factors of lower mineral bone density?

Answer 18

• Steriod therapy
• CF related diabetes
• Dec physical activity
• Calcium, vit D + K deficiency
• Chronic inflammation

Question 19

Why are CF patients infertile?

Answer 19

Due to congenital bilateral absence of vas deferens

Question 20

What nebulised antibiotics are used in p. aeruginosa?

Answer 20

Colistin + tobramycin