Cystic Fibrosis Flashcards
Define Cystic Fibrosis
Cystic fibrosis is a auto recessive genetic condition. It’s caused by a faulty CFTR gene on Chr7 that affects the movement of salt and water in and out of cells. This, along with recurrent infections, can result in a build-up of thick, sticky mucus in the body’s tubes and passageways – particularly the lungs and digestive system.
There are decreased luminal Cl secretion and Increased Na reabsorption leading to viscous secretions.
In the sweat glands, there is decreased Cl and Na reabsorption so there is salty sweat.
Explain the aetiology/ risk factors for cystic fibrosis
CF is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), an anion channel found in the apical membrane of epithelial cells. Patients may be either homozygous or heterozygous with respect to CFTR mutations. Carriers of one CFTR mutation and one normal CFTR allele do not demonstrate disease in most cases.
Mutations in CFTR result in abnormal salt transport by epithelial cells, resulting in thick, sticky secretions.
- In the pancreas, this leads to blockage of exocrine ducts, early activation of pancreatic enzymes, and eventual autodestruction of the exocrine pancreas. Therefore, most patients require supplemental pancreatic enzymes.
- In the intestine, bulky stools can lead to intestinal blockage.
- In the respiratory system, the absence of CFTR function results in mucus retention, chronic infection, and inflammation that eventuate in the destruction of lung tissue.
Risk factors:
- FHx of CF
- known carrier status of both parents
- ethnicity - northern europeans
Organisms in CF:
- early: S.aureus, H.influenza
- late: P.aeruginosa, B. cepacia
Summarise the epidemiology of cystic fibrosis
10500 people in the UK
The incidence among white people is about 1/3000; the incidence is lower among people of African, Hispanic, and Asian descent.
Recognise the presenting symptoms of cystic fibrosis
Neonates:
- failure to thrive
- meconium ileus
- rectal prolapse
Children/YA:
- Nose: nasal polyps, sinusitis
- Resp: cough, wheeze, infections, bronchiectasis, haemoptysis, pneumothorax, cor pulmonale
- GI: pancreatic insufficiency, DM, steatorrhoea, Distal instestinal obstruction syndrome, gallstones, cirrhosis
- other: male infertility, osteoporosis, vasculitis
Recognise the presenting signs of cystic fibrosis
Clubbing ±HPOA (hypertrophic pulmonary osteoarthropathy, clubbing + periostitis)
Cyanosis
Bilateral coarse creps
Identify the appropriate investigations for cystic fibrosis
Diagnosing CF:
- Sweat test: Na and Cl > 60mM
- Genetic screening for common mutations (need 2 disease causing mutations)
- Faecal elastase (pancreatic exocrine function)
- Immunoreactive trypsinogen (neonatal screening)
Investigations:
- Bloods: FBC, LFTs, Clotting, ADEK levels, GlucTT
- Sputum: MCS
- Throat swab
- CXR: bronchiectasis ±sinus XR
- A/US: fatty liver, cirrhosis, pancreatitis
- Spirometry: obstructive patterns
- Serology: aspergillus, + skin test
Generate a management plan for cystic fibrosis
General:
- MDT: physician, GP, dietician, physio, specialist nurse
Chest:
- Physio: postural drainage, forced expiratory techniques, expectoration
- ABx: acute infections and prophylaxis (azithromycin)
- Mucolytics: DNAses
- Bronchodilators ±Inhaled corticosteroids if asthma
- Vaccinations
GI:
- Pancreatic enzyme replacement - pancreatin Creon
- ADEK supp
- Insulin
- Urso-deoxy-cholic acid for impaired hepatic fx, stimulates bile secretion
- Stool softeners, hydration
- H2RAs or PPIs for GORD
Advanced lung disease:
- O2
- diuretics
- heart/lung transplant
- NIV
Other:
- Rx of complications - DM
- Fertility and genetic counselling
- DEXA for osteoporosis screen
Identify possible complications of cystic fibrosis
Pneumothorax/ haemothorax
Cor pulmonale
Acute respiratory failure
Chronic resp acidosis
Cirrhosis
Intussusception
Distal intestinal obstruction syndrome
DM
Osteoporosis
Summarise the prognosis of cystic fibrosis
Improved expectancy due to novel therapies
Mean life expectancy 40-50 years
