Cystic fibrosis Flashcards
Describe the inheritance pattern of cystic fibrosis
Autosomal recessive
How many Caucasians are carriers of CF gene?
1 in 25
What is cystic fibrosis?
Multisystem dysfunction caused by mutation in CF transmembrane conductance regulator gene (CFTR)
Life long and life limiting disease
What is the commonest CF mutation?
F508 deletion
What is the CFTR protein?
Chloride channel present in numerous epithelial tissues - drives chloride against its concentration gradient using ATP
Present on airway epithelial cells and submucosal glands
What happens when there is a defective CFTR protein?
Disruption in chloride ion and sodium movement
Reduces amount of water in secretions
Reduced surface liquid and thicker secretions
Describe the effects of CF in the lungs
Reduced clearance and thicker secretions predisposes to more infections
Can lead to bronchiectasis
Describe the effects of CF in the pancreas
Pancreatic duct occluded in utero
Permanent damage to the exocrine pancreas
Pancreatic insufficiency
Describe the effects of CF in the GI tract
Small intestine viscous mucus causes bowel obstruction in utero - meconium ileus
Biliary tree - cholestasis - neonatal jaundice
Distal intestinal obstruction syndrome later in life
Describe the effects of CF in the reproductive tract
Males - absence of vas deferens
What do the clinical features of CF depend on?
Age of patient
Describe features of CF in neontaes
Meconium ileus
Failure to thrive
Prolonged neonatal jaundice
What does meconium ileus present with?
First days of life
Failure to pass meconium
Abdominal distension
Bilious vomiting
Describe features of CF in infants
Failure to thrive
Recurrent chest infections
Steatorrhea
Describe features of CF in childhood
Nasal polyps
Rectal prolapse
Sinusitis
Describe features of CF in adolescence
DM Chronic liver disease DIOS Gallstones Liver cirrhosis
What are the key aims of management of CF
Early treatment of infections
Optimising nutrition
Give some examination findings of CF
Finger clubbing
Nasal polyps
Chest - hyperinflated, crepitations, portacath
Abdomen - faecal mass (if constipated/DIOS), scar from ileostomy (meconium ileus)
How is cystic fibrosis diagnosied
Clinical findings + positive sweat test + 2 identified mutations (may support diagnosis)
What investigations are useful in CF
CXR - hyperinflation and bronchial thickening
Chloride sweat test - at diagnosis and annually if in receipt of CFTR corrector therapy
Microbiological assessment - cough swab/sputum sample
Glucose tolerance test - annual assessment and teenage
Liver function and coagulation - annual assessment
Bone profile - annual assessment
Lung function - spirometry
Faecal elastase - pancreatic function
Chest CT - bronchiectasis
Genetic analysis
What is a problem with the chloride sweat test?
Baby might be too small so not enough sample may be obtained
False negatives and false positives
What concentration of sweat chloride is suggestive of CF?
> 60mmol/L
Describe the management of CF
MDT
Patient and family education
Airway clearance and BD chest physio, mucolytic and DNase (reduces viscosity of mucous by digesting DNA in the sputum), hypertonic saline (can aid airway clearance)
Nourishment and exercise - pancreatic enzyme supplementation (Creon), fat soluble vitamin supplements, monitor growth, dietician input, build up milkshakes to supplement meals
Continuous microbial assessment and 2 weeks of antibiotics to treat respiratory infections even if asymptomatic
Infection control - different clinics for those with different bacteria, side room if admitted
Monitor complications
Annual review
CXR
Glucose tolerance test >age 12
What bacteria are common to CF patients?
Staphylococcus aureus
Haemophilus influenza
Pseudomonas aeruginosa - can be chronic
Which antibiotic has been shown to reduce exacerbations even in patients without chronic Pseudomonas infection?
Azithromycin
List the complications of CF
Allergic bronchopulmonary aspergillosis Bronchiectasis Haemoptysis Pulmonary hypertension and right heart strain Pneumothorax Respiratory failure Nasal polyps and sinusitis Rectal prolapse Distal intestinal obstruction syndrome CF liver diseases - cholestasis, gallstones and liver cirrhosis CF related diabetes Delayed puberty Arthritis Reduced bone mineral density Sub/infertilty
Describe distal intestinal obstruction syndrome
Obstruction at the distal ileum
Colicky abdo pain with mass in RLQ
What is CF related diabetes associated with?
Rapid decline in lung function and disease progression
