Cystic Fibrosis Flashcards
What is cystic fibrosis?
An autosomal recessive disorder most commonly caused by a mutation (∆F508) in the CFTR gene on chromosome 7, leading to thickened secretions in the lungs and GI tract.
What is the most common genetic mutation in cystic fibrosis?
∆F508 deletion in the CFTR gene on chromosome 7.
What is the primary defect in cystic fibrosis?
Abnormal chloride transport leading to thick mucus secretions in the lungs, pancreas, and other organs.
What GI condition is highly associated with CF in neonates?
Meconium ileus (bilious vomiting, failure to pass meconium, microcolon on imaging).
How does meconium ileus differ from duodenal atresia?
Meconium ileus: Dilated bowel loops, microcolon.
Duodenal atresia: Double bubble sign on x-ray, association with Trisomy 21.
What are other GI conditions that can present similarly to meconium ileus?
Duodenal atresia, jejunal/ileal atresia (triple bubble sign), Hirschsprung disease, and malrotation with volvulus.
What are the major features of cystic fibrosis?
In children, failure to thrive (less than 2nd percentile). Pancreatic insufficiency. Chronic cough. Recurrent respiratory infections. Lung diseases like bronchiectasis and obstructive lung disease. On spirometry, there is usually an obstructive pattern characterized by decreased forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC). Because the decrease in FEV1 is more profound, FEV1/FVC ratio is also reduced. The airway obstruction prevents full expiration (ie, causes air trapping), leading to increased residual volume (RV) and hyperinflated lungs with increased total lung capacity (TLC). This progressive increase is clinically apparent by a barrel-shaped chest on examination and lung hyperexpansion on x-ray.
What is the long-term pulmonary complication of CF?
Bronchiectasis, leading to chronic airway inflammation and irreversible lung damage. The lungs are the predominant organ affected in CF due to the accumulation of viscous secretions in the airways. Bacteria colonize the airways and cause recurrent infection and chronic inflammation that eventually leads to scarring of the bronchial walls (ie, bronchiectasis). Progressive bronchiectasis (ie, weakened, dilated bronchioles that collapse easily) and mucus-plugging result in obstructive lung disease.
What are the most common respiratory pathogens in CF patients by age?
Staphylococcus aureus (infants, young children), Pseudomonas aeruginosa (adolescents, adults).
What bacteria should always be covered in CF exacerbations?
Pseudomonas aeruginosa and Staphylococcus aureus.
What GI conditions are associated with CF?
Pancreatic insufficiency, fat-soluble vitamin malabsorption (ADEK), rectal prolapse, and meconium ileus.
What test is used to assess pancreatic insufficiency in CF?
Fecal elastase (low in pancreatic insufficiency).
What hepatobiliary disease is seen in CF?
Biliary cirrhosis and hepatosteatosis due to thick bile secretions.
What reproductive issues are seen in CF?
Males: Congenital absence of the vas deferens (azoospermia, infertility).
Females: Thick cervical mucus causing subfertility.
Can women with CF become pregnant?
Yes, but thick cervical mucus can cause difficulty conceiving.
What is the gold standard diagnostic test for CF?
Sweat chloride test (elevated chloride levels >60 mmol/L).
What newborn screening test is used for CF?
Immunoreactive trypsinogen (IRT) test, followed by CFTR genetic testing if positive.
What other diagnostic test can be used for CF?
Nasal potential difference testing (abnormal in CF).
What is the cornerstone of CF respiratory management?
Airway clearance therapies: Hypertonic saline, DNase, chest physiotherapy.
What medications are used to treat CF airway obstruction?
Inhaled beta-agonists (e.g., albuterol) for reversible obstruction.
What CFTR modulators are used for the ∆F508 mutation?
Ivacaftor, Lumacaftor, Tezacaftor.
What is the role of azithromycin in CF management?
Used chronically to reduce exacerbations and inflammation.
When is ibuprofen used in CF?
To slow lung function decline in children with mild disease.
What is the antibiotic regimen for CF exacerbations?
Coverage for Staphylococcus aureus and Pseudomonas aeruginosa with beta-lactam + aminoglycoside (e.g., ceftazidime + tobramycin).
When is lung transplantation considered in CF?
End-stage respiratory failure with severe bronchiectasis and declining lung function.
What are the major organs affected by CF?
Lungs, pancreas, hepatobiliary system, intestines, reproductive system.
What electrolyte abnormality is seen in CF patients?
Hyponatremia due to excessive salt loss in sweat.
What should you suspect in a newborn with bilious vomiting and failure to pass meconium?
Meconium ileus, highly suggestive of CF.
What test should be performed if a young child presents with recurrent respiratory infections and failure to thrive?
Sweat chloride test to rule out CF.
Which bacterial infection becomes more common as CF patients age?
Pseudomonas aeruginosa replaces Staphylococcus aureus as the most common respiratory pathogen.
