Respiratory II Flashcards
What are the common presenting features of cystic fibrosis?
Neonatal period:
- Meconium ileus
- Prolonged jaundice (less common)
General:
- Recurrent chest infections
- Malabsorption: steatorrhoea, failure to thrive
- Other features: liver disease
What are the other features of cystic fibrosis?
- Short stature
- Diabetes mellitus
- Delayed puberty
- Rectal prolapse (due to bulky stools)
- Nasal polyps
- Male infertility, female subfertility
What is cystic fibrosis?
An autosomal recessive disorder causing increased viscosity of secretions (eg. lungs and pancreas)
What is the pathophysiology of cystic fibrosis?
Defect in the cystic fibrosis transmembrane conductance regulator gene (CFTR), which codes a cAMP-regulated chloride channel
What are the specific mutations causing cystic fibrosis?
80% due to delta F508 on the long arm of chromosome 7
Which organisms may colonise cystic fibrosis patients?
- Staph aureus
- Pseudomonas aeruginosa
- Burkholderia cepacia
- Aspergillus
What are the diagnostic investigations for cystic fibrosis?
- Abnormally high sweat chloride
- Normal <40mEq/l, CF indicated by >60mEq/l
- Newborn screening via the heel prick test
What can cause a falsely positive sweat test?
- Malnutrition
- Adrenal insufficiency
- Glycogen storage diseases
- Nephrogenic diabetes insipidus
- Hypothyroidism, hypoparathyroidism
- G6PD
- Ectodermal dysplasia
What’s the most common reason for a false negative sweat test?
Skin oedema often due to hypoalbuminaemia/ hypoproteinaemia secondary to pancreatic exocrine insufficiency
What are the key points of managing cystic fibrosis?
- Regular (at least x2 per day) chest physiotherapy and postural drainage
- Prophylactic antibiotics, bronchodilators and medicines to thin secretions (eg. dornase alfa)
- High calorie diet, including fat intake
- Minimising contact with other CF patients
- Fat soluble vitamin supplementation (ADEK)
- Pancreatic enzymes taken with meals (eg. Creon)
- Regular immunisation with influenza and pneumococcal vaccines
- Lung transplantation (patients with end-satge pulmonary disease)
What is a contraindication for lung transplantation for patients with CF?
Chronic infection with Burkholderia cepacia
Why should CF patients minimise contact with each other?
To prevent cross infection with Burkholderia cepacia complex and Pseudomonas aeruginosa
What medication is used to treat CF patients homozygous for the delta F508 mutation?
Lumacaftor/ Ivacaftor (Orkambi)
What is the moa of Lumacaftor?
It increases the number of CFTR proteins that are transported to the cell surface
What is the moa of Ivacaftor?
It’s a potentiator of CFTR that is already at the cell surface, increasing the probability that the defective channel will be open and allow chloride ions to pass through the channel pore
