Cystic Fibrosis Flashcards
How many people carry the CF gene?
1 in 25 people
How does a defect in the CFTR gene cause cystic fibrosis?
The CFTR protein doesn’t function
You cannot pump chloride ions out of your cells
It also inhibits the positive feedback of ORCC and the negative feedback of ENAC
Overall less Cl- is pumped out and more Na+ is pumped in meaning water moves into the cells be osmosis and mucus secretions become sticky
What does CFTR stand for?
Cystic Fibrosis transmembrane conductance regulator
What are the different classes of CFTR gene defects?
Class 1-5
Class 1 = no CFTR synthesis- often death in utero
Class 2 = CFTR trafficking defect (deltaF508 amino acid deletion) very severe CF
Class 3 = CFTR gets to the membrane but doesn’t open. Disregulation of CFTR diminished by ATP binding and hydrolysis
Class 4 = Defective chloride conductance or channel gating. CFTR channel doesn’t open in response to the correct stimuli
Class 5 = Reduced CFTR transcription and synthesis.
What causes CF?
A mutation in the CFTR gene on chromosome 7
What is the most serve and mild class of cystic fibrosis?
Class 1 is the most severe and class 5 the most mild
What is the most common gene mutation for CF with an occurrence of 70%?
deltaF508- deletion of phenylalanine at position 508 on chromosome 7.
Cyctic fibrosis is autosomal recessive but you can have different CF mutations on each copy of the gene. True or false?
True
What are the symptoms and signs of CF?
Salty sweat Intestinal blockage Fibrotic pancreas Failure to thrive Recurrent bacterial lung infections Congenital bilateral absence of vas defrens Gall bladder and liver disease Filled sinuses
Who would get a CF genetic test as an adult?
Bronchiectasis under 40 Upper lobe bronchiectasis Colonisation with Staph aureus Infertility Very low weight
What is the prophylactic management for CF?
Antibiotics:
Staph aureus = oral fluclox or oral cotrim
Pseudomonas = oral azithromycin, neb colomycin, neb/inhaled tobramycin, neb aztreonam
How are the pancreatic issues managed in CF?
1) Exocrine failure
2) Endocrine failure
1) CREON- enables patients to absorb energy
2) INSULIN- cannot be managed on metformin.
Annual glucose tolerance test and continuous glucose monitoring used by some.
How are the bowel issues managed in CF?
GASTROGRAFFIN (treatment), LAXATIVES (prophylaxis)
Fluid and exercise help
What are the liver problems in CF?
Sludging up of hepatic ducts( both intrahepatic and extra hepatic (bile ducts))
Portal hypertention => portal-systemic anastamosis, variceal bleeding and hepatic encephalopathy
How are the liver problems managed in CF?
TIPSS- Transjugular intrahepatic porto-systemic shunt
Inseert a tube to equalise the pressure between the portal and systemic circulation.
Reduces anastamoses and bleeding risk but increases encephalopathy risk
