CF Flashcards
What is Cystic fibrosis
Defect in CFTR gene on chromosome 7
Functions as chloride channel
Range of severity depending on mutation
What gene causes 70%
Phe508del / deltaF508
How is it transmitted
AR
What are different classes of mutation
Class 1 - no synthesis Class 2 - no maturation Class 3 - CFTR doesn't work Class 4 - decreased conductance Get milder
What population is carrier and affected
1 in 25 carrier
1 in 2500 affected
What does CFTR do / patholophysiology behind CF
Active transport of chloride and Na
Regular volume on epithelial surface giving cilia normal function
Abnormal viscosity interfere with clearance leading to bacteria colonisation and repeated infections
- Cilia collapse
- Excessive inflammation
Increased Na and decreased Cl inactive defences
Abnormal mucous builds up which traps bacteria
Affects other tracts e.g. GI / pancreas
- Lack of digestive enzymes
- Lack of pancreatic/ biliary secretion
What does reduced chloride out and increased Na in lead too
Inactivates defences in airway as high salt
CF have abnormal mucous glycoprotein which acts as binding site for bacteria
What are antenatal features
Echogenic bowel
Perforated meconium ileum
What are neonatal features
Pick up on Guthrie neonatal screen - increased trypsinogen Meconium ileus Gut aresia Obstructive Jaundice Vitamin deficiency so low cognition Steatorrhoea
What are features in children
Recurrent chest infection Chronic cough Constipation due to dysmotiltiy FTT Rectal prolapse Pseudobarttlers Pancreatic insufficiency -steatthorea and DM Delayed puberty
What are common organisms in CF / chronic
S.Aureus H. influenza S.pneumonia Klebsiella E.coli Fungal Mycoplasma = chronic Pseudomona's - form biofilm so resistant and very difficult to get rid of so chronic Burhoderi cepaci - cause rapid progression so PCR
What are less common organisms
Mycobacterium abscess
Genovar III
What do the less common organisms lead to
CI to transplant
What are the signs of pancreatic insufficiency in CF
Failure to gain weight / FTT Fat malabsorption Vitamin deficiency - ADEK Steatorrhea Offensive stools DM Gall stones Biliary cirrhosis
What do recurrent chest infections cause / resp complications
Obstruction = wheeze Pneumonitis Bronchiectasis Pneumothorax Resp failure Abscess Hypertrophy of artery = haemoptysis Cor pulmonale Scarring and difficult to inflate lungs / SOB Abscess Cyanosis Clubbing Coarse crackles
What do adults also often have
Nasal polyps Clubbing Sinusitis Male infertility Chronic pancreatitis Gall stones Cirrhosis DM Short stature Pseudo-bartter Osteporosis Vasculitis
What is pseudo-battler
Hypokalaemia Alkalsois Hyperaldosterone Normal BP Hypokalameic hypochlroamic metabolic alkalosis in absence of renal pathology
How do you screen CF
Neonatal screening
High immunoreactive trypsinogen
If +ve = sweat test which is gold standard + genetic test of blood / saliva
How do you Dx CF
Sweat test
CXR
CT
Bloods - FBC, U+E, LFT
Clotting + Vit ADEK due to malabsorption
Faecal elactase = pancreatic enzyme that is raised
Sputum culture to look for bacterial colonisation
Glucose tolerance test annually
Spirometry = obstructive
Abdo USS
What is the sweat test
Failure to absorb CL so if >60 in sweats suggests CF
What gives false +Ve
Malnutrition Adrenal insufficeincy Glycogen storage disorder DI Hypothyroid G6PD
What gives false -ve
Skin oedema due to pancreatic insufficiency
What does CXR show
Scarring
HYperinflation
Cyst
Bronchial dilation
What does CT show
Dilated airway
Thickened wall
Pus
