Lower respiratory tract diseases - CYSTIC FIBROSIS Flashcards
what is cystic fibrosis?
an INHERITED cause of severe bronchiectasis.
what gene passes on cystic fibrosis?
autosomal recessive
what leads to respiratory failure & death in cystic fibrosis?
- viscous circle of mucous stasis
- inflammation
- infection
what does CFTR stand for?
cystic fibrosis transmembrane conductance regulator
what causes cystic fibrosis?
autosomal recessive mutations of the gene encoding the CFRT.
what is CFTR?
a transmembrane chloride channel found in the respiratory epithelium, exocrine gland and sweat ducts.
- by transporting chloride ions across the cell membrane, CFTR controls the movement of sodium and water out of the cell and into the mucous later
- this movement of water is necessary for the production of thin, free flowing mucus.
what happens if the CFTR functions poorly?
- chloride flow across cell membrane is impaired
- mucous is inadequately hydrated and becomes thick and sticky
what are the 5 classes of defects in the CFTR and what effect do each of them have.
1) Class 1
- defective protein synthesis
- no CFTR made
2) Class 2
- defective protein processing
- CFTR os stuck within the cytosol
3) Class 3
- protein is made but there is defective Chanel regulation
4) Class 4
- not much protein is passed through, therefore, defective chloride conductance
5) Class 5
- reduced synthesis because of unstable messenger RNA
how does pancreatic damage & failure arise?
when mucus blocks the pancreatic ducts
clinical features of cystic fibrosis?
- chronic phlegm production and daily cough
- recurrent respiratory infections
- breathlessness
- wheeze
- pneumothorax
- bronchiectasis
- nasal polyps
- haemoptysis
GI;
- pancreatic insufficiency
- gallstones
- cirrhosis
Other;
- male infertility’s
- osteoporosis
- arthritis
- vasculitis
- nasal polyps
- sinusitis
- hypertrophic pulmonary osteoarthropathy
describe 3 crucial differences between cystic fibrosis and bronchiectasis?
Cystic fibrosis;
- starts in early childhood
- usually worse in lung apices
- almost always results in fatal respiratory failure due to severe airway obstruction
what are SIGNS of cystic fibrosis?
- finger clubbing
- low body mass
- extensive CREPITATIONS in both lungs
- obvious signs of airway obstruction with poor respiratory function
what are the clinical features of cystic fibrosis OUTSIDE the respiratory system?
- infertility in males
- abnormal liver function tests
- meconium ileus in neonates
- glucose intolerance and diabetes
- pancreatic insufficiency with malabsorption and deficiency of vitamins A, D & K
- chronic sinusitis
- osteoporosis
when are most cystic fibrosis diagnosis made?
most are made at newborn screening.
- involves measuring immuno-reactive trypsinogen at the time of neonatal heel prick test.
- if the conc is raised, formal testing is performed.
what are diagnostic methods are used?
- common clinical features
- CFTR functional testing; the SWEAT TEST. this measure Cl- ion concnenntrationn, if its high it indicates cystic fibrosis.
- confirm it with genetic testing
