Cystic Fibrosis Flashcards
What is cystic fibrosis?
What is the most common mutation associated with CF?
Autosomal recessive condition caused by mutation to the transmembrane conductance regulatory gene on chromosome 7
Delta-F508
-codes for chloride channel
What are the consequences of cystic fibrosis mutation?
Blockage of pancreatic and biliary ducts
- thick secretions
- leads to lack of digestive enzymes= pancreatic lipase
Recurrent airway infections
-low volume thick airway secretions leads to reduced airway clearance and bacterial colonisation
Male infertility
-bilateral abscence of vas deferens leading to healthy sperm being unable to reach the testes for ejaculation
When is cystic fibrosis commonly diagnosed and why?
At birth
Due to the babies having heel prick test (bloodspot test) which screens for CF
What is often the first sign of cystic fibrosis?
Meconium ileus = pathognomoninc of CF
- not passing meconium within 24 hrs
- abdo distention
- vomiting
Meconium is the 1st stool which newborns pass
In babies with CF, stool is very thick and sticky leading to them having difficulty passing the stool and it becoming stuck and obstructing the bowels
How might someone with CF present?
Chronic cough
Thick sputum production
Recurrent respiratory tract infections
Steatorrhea= due to lack of lipase leading to poor digestion of dietary fats
Abdo pain and bloating
Failure to thrive
Taste salty when parents kiss child= due to their sweat being concentrated with salt
Finger clubbing
Crackles and wheezes
Abdo distention
What are the 3 methods used to diagnose CF?
Newborn blood spot testing
Sweat test= gold standard for diagnosis
Genetic testing for CFTR gene
-via amniocentesis or chronic villous sampling
How is a sweat test performed and what is the theory behind it?
Pilocarpine applied to skin
Electrodes applied to either side of this area and current passed through to cause the area to sweat
Sweat absorbed onto gauze or filter paper and sent for chloride concentration testing
>60mmol/L chloride= DIAGNOSTIC
Defective CFTR in sweat gland leads to reduced transport of sodium chloride in reabsorptive duct leading to the sweat having a higher concentration of sodium chloride which can be quantified with a sweat test
What is the normal function of CFTR?
Normal function of CFTR:
-movement of Cl- ions against concentration gradient into mucus to increase the electrolyte concentration of the mucus and cause water to be drawn down osmotic gradient to thin the mucus
What microbes are people with CF at risk of being colonised by and why?
Staphylococcus aureus
Pseudomonas aeruginosa
Thicker secretions means the mucociliary escalator cannot clear the mucus which then provides the perfect environment for microbials to colonise
How is somone with CF managed?
Chest physiotherapy
-acts to clear mucus to reduce the risk of infection
Exercise
-improves respiratory function and reserve
High calories diet
-due to malabsorption, increased respiratory effort, coughing and infections and physiotherapy
CREON tablets
-CF patients can suffer from pancreatic insufficiency, so need pancreatic enzymes replacing
Prophylactic flucloxacillin
-reduce risk of bacterial infections
Bronchodilators i.e. salbutamol
Nebulised DNase
-breaks down DNA material in secretions to make the secretions less viscous
Nebulised hypertonic saline
-acts as mucolytic
Vaccinations
-flu/pneumococcal/varicella
What other conditions do patients with CF need monitoring for?
Diabetes
- blockage of pancreatic ducts can induce inflammation which leads to scarring of the pancrease
- can cause damage to beta-cells leading to decreased insulin production
Osteoporosis
-poor mineral absorption can lead to decreased bone mineralisation and also increased bone resorption
Vitamin D deficiency
Liver failure
-can be due to problems in bile ducts or due to induced scarring/cirrhosis of the liver
