Cystic Fibrosis Flashcards
What is cystic fibrosis, include:
- Inheritence pattern
- Gene mutation
- Location of gene
- Secretions
- Where in body it affects
- Autosomal recessive
- CFTR (cystic fibrosis transmembrane conductance regulator)
- Chromosome 7
- Charcterised by thick secretions
- Can lead to multisystem disease- most commonly affects respiratory system and GI tract
Explain why cystic fibrosis leads to thick mucus
- Defect in CFTR gene
- Defective CFTR protein
- CFTR codes for Cl- ion channel. In the airways, CFTR also inhibits ENaC
- Hence, in healthy individual, Cl- is transported into lumen and the movement out of Na out of lumen is reduced; the net effect of this is increased water in the lumen (and hence in secretions)
- In CF pt, Cl- transport is reduced and the ENaC are not inhibited hence Na+ moves out of lumen; the net effect of this is decreased water in the lumen
Explain why people with cystic fibrosis have salty sweat
- In sweat glands, CFTR is responsible for reabsorption of Cl- through CFTR; it also regualtes Na+ reabsorption thorugh ENaC
- CFTR mutation means less reabsorption of Na+ and Cl- hence salty sweat
Function of the CFTR is tissue specific; true or false?
True (you can see from pathophysiology behind thick secretions and salty sweat that CFTR in resp tract works differently to CFTR in sweat glands. Main idea is that it regualtes Cl- and Na+ transport)
When do symptoms of CF often start?
- Symptoms often start in early infancy
- However, in milder cases symptoms may not appear until later in childhood
- Genetic testing allows for early detection & treatment
Discuss the symptoms of cystic fibrosis include symptoms of a:
- Newborn
- Children & young adults
Newborn
- Meconium ileus
- Failure to thrive
- Rectal prolpase
- Voracious appetite (never satisfied)
Children & Young Adults
- Respiratory
- Cough
- Wheeze
- Recurrent infections
- Haemoptysis
- GI
- Steatorrhoea
- Symptoms of diabetes (thirst, polyuria, polydipsia)
- Distal intestinal obstruction syndrome
- Gallstones
- GORD
- Symptoms of liver cirrhosis
- Other
- Male infertility
- Sinusitis
- Osteoarthritis
- Nasal polyps
What is meconium ileus?
In what % of infants, with CF, does it present in?
- Meconium (baby’s first stool) is blocking the ileum because it is very thick; leads to symptoms of: vomitting, abdo distension, delay in passing meconium
- 15-20%
What % of CF patients have malabsorption?
At what age is this most evident?
- >90%
- Infancy
Discuss what you might find on clinical examination of someone with CF
- Finger clubbing
- Bilateral coarse crackles
- Evidence of pneumothorax (e.g. hyperesonant percussion, decreased breath sounds, decreased expansion etc..)
- Cyanosis
- Evidence of malnutrition
- Mass in right lower quadrant of abdomen (DIOS)
Discuss how we diagnose CF
To diagnose CF need one or more of:
- Characteristic phenotypic features of CF
- History of CF in sibling
- Positive newborn screening test
And also need one of:
- Increased NaCl concentration in sweat (positive sweat test)
- Identification of two CF mutations via genotyping
- Demonstration of abnormal nasal epitihelial ion transport (nasal potential difference)
What test is the best indicator of CF?
NaCL sweat test
Discuss what investigations you would do if you wanted to diagnose CF
- If newborn, do heel prick test (immunoreactive-trypsinogen test)
- Sweat test
- Genetic testing
What value indicates a:
- Negative sweat test
- Intermediate result
- Positive sweat test
- Negative: <30mmol/L
- Intermediate: 30-59mmol/L
- Positive: >/=60mmol/L
Explain why pancreatic insufficiency is a common symptom of CF
Explain why CF can lead to diabetes
- Thickened secretions mean that overall secretion from pancreas is reduced.
- Blocked secretions cause inflammation which leads to scarrring which leads to impaired production of insulin from pancreas
State some symptoms of pancreatic insufficiency in CF patients
- Steatorrhoea
- Abdo pain
- Excess flactulence
- Weight loss
Discuss how we manage cystic fibrosis, think about treating:
- Respiratory problems
- Pancreatic/GI/malabsorption problems
- Psychological/emotional
Respiratory Problems
- Chest physio with postural drainage
- Mucolytics e.g.Inhaled recombinant human deoxyribonuclease 1
- Bronchodilators
- Antibiotics for acute infective exacerbations (usually give 2 antibiotics to reduce antibiotic resistancE)
- Prophylactic antibiotics (azithromycin 3x weekly proven to help)
- Inhaled antibiotics
- ICS
- Flu vaccination
- Lumacaftor-ivacaftor
- Lung transplant (in resp failure)
Pancreatic/GI/malabsorption problems
- Pancreatic enzyme replacement
- Fat soluble vitamins
- Supplements
- High calorie intake
- NG or PEG feeding
Psychological/emotional
- Support groups
- Counselling
