Paeds: Cystic fibrosis HW Flashcards
Carrier rate
1/25
Birth rates
1/2500
Commonest ethnic group
Caucasians
Genetics
- Autosomal recessive
- Gene located on chromosome 7
- > 800 different gene mutations cause CF - commonest is FR08 blocker.
Gene on Chromosome 7 function
- Codes for protein called cystic fibrosis transmembrane regulator (CFTR) - mutated in CF.
- CFTR is a cyclic AMP-dependant chloride channel blocker.
Pathophysiology
- Abnormal ion transport across epithelial cells of exocrine glands in respiratory tract and pancreas.
- -> Leads to: Reduced Cl- excreted into airway lumen, raised Na absorption, water follows = raised viscosity of secretions.
- Abnormal function of sweat glands
- CFTR also affects inflammatory processes and defence against infections.
Sweat gland pathophysiology
= raised conc. of Na and Chloride in sweat (80-125 mmol/L in CF, 10-14 mmol/L normal)
Symptoms in infancy
- Meconium ileus
- Prolonged neonatal
- Failure to thrive
- Recurrent chest infections
- Malabsoprtion and steatorrhoea
Meconium ileus
10% in neonatal period
- Thickened meconium causes IO with vomiting, abdo distention and failure to pass meconium in first few days of life.
Recurrent chest infections
- Viscid mucus in smaller airways predisposes to c.i.
- Leads to damage of bronchi wall, bronchiectasis and abscess formation
Common organisms of chest infections
Staph aureus
Haemophilius influenza
Strep pneumoniae
Psuedomonas aeruginosa
Symptoms of chest infections
Persistent, loss cough productive of purulent sputum
Signs of chest infections
Hyperinflation
Coarse crepitations or expiratory rub ± finger clubbing
Malabsorption and steatorrhoea
- Due to insufficiency of the pancreatic exocrine enzymes (lipase, amylase, proteases)
- Pass large, pale, offensive, greasy stools throughout day.
Young child symptoms
Bronchiectasis (chronic dilation of bronchi)
Rectal prolapse
Nasal polyp
Sinusitis
Older child, Adolescent and Adult symtpoms
- DM (either IDDM or NIDDM)
- Cirrhosis and portal hypertension
- Distal intestinal obstruction
- Pneumothorax/ recurrent haemoptysis (cough up blood)
- Persistent Psuedomonas infection
- Aspergillosis
- Male infertility
- Women have reduced fertility
- increased psyhological problems
Distal intestinal obstruction
Viscid mucofaeculent material obstructs bowel.
Persistent infections to think of
Some also have Burkholderia cepacia which markedly reduces lung function - spread is from person to person to CF patients are advise not to socialise with other CF sufferers.
Male infertility due to
Abnormalities in vas deferens
Pregnancy and breast feeding :
Caution that their breast milk has a high sodium concentration
Diagnosis
Sweat test
CXR
Also: IRT/DNA, malabsorption screen, glucose tolerance test, lung function tests, sputum culture
Sweat test
- Stimulated by pulocarpine iontophoresis -collected int a capillary tube or absorbed onto a weighed piece of filter paper.
- Diagnostic error if inadequate volume of sweat - do two tests to confirm results.
- Sweat Chloride >60 mmol/L = CF (
CXR
Hyperexpansion,
peribronchial shadowing, bronchial wall thickening,
ring shadows
Screening newborns infants
- Immunoreactive trypsin (IRT) is increased in CF patients
- Confirm with a sweat test
- Screening in antenatal carrier-status testing is possible
- Pre-implantation analysis after IVF at 8 cell stag (one cel removed and analysed - only embryos without CF re-implanted.
