Cystic Fibrosis Flashcards
Heritability of CF?
Autosomal recessive
What is CF caused by?
Abnormal gene coding for cystic fibrosis transmembrane regulator protein (CFTR) on chromosome 7
What type of protein is CFTR?
cAMP-dependent chloride channel blocker
Most common mutation in CF?
^F508 (^ meant to be a triangle)
Pathophysiology of CF?
Poor transport of chloride ions and water across epithelial cells of the respiratory and pancreatic exocrine glands result in an increased viscosity of secretions
Presentation of CF? (both adult + neonatal)
Adults
- recurrent chest infections
- failure to thrive due to malabsorption
- liver disease
Neonates
- prolonged neonatal jaundice
- bowel obstruction (meconium ileus)
- rectal prolapse
Investigation/diagnostic test for CF?
The sweat test
How does the sweat test work?
Sweat stimulated by pilocarpine iontophoresis, collected on filter paper, and analysed for NaCl concentration
- the abnormal function of sweat glands in CF results in excess concentration of NaCl in sweat
What are the expected sweat test results for a CF patient and a “normal” patient?
CF - NaCl = 80-125mmol/L
Normal - NaCl = 10-14mmol/L
How many times do sweat tests need to be performed and why?
At least 2 tests should be performed
- diagnostic errors and false positives are common
Management of CF?
Physiotherapy - for respiratory secretions
Antibiotics - for prophylaxis and treatment of lung infections
Pancreatic enzyme supplements - for prevention of malabsorption
Complications of CF?
Diabetes Hepatic cirrhosis Male infertility Severe pulmonary hypertension + cor pulmonale Chronic lung infections
How are cases of CF identified mostly nowadays?
National screening programme assesses immunoreactive trypsin levels (IRT)
How are the levels of IRT changed in CF?
IRT increased in CF
