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What are the regulatory functions of the cystic fibrosis transmembrane conductance regulator (CFTR)?
- 1. ion transport (chloride, bicarbonate, sodium)
- 2. pulmonary inflammation
- 3. bacterial adherence
- 4. mucus rheology
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What secondary messerger is the CFTR affected by?
cAMP
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CFTR allows ions to follow what type of gradient?
electrochemical
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What occurs in a Class I CFTR defect?
protein not synthesized
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What occurs in a Class II CFTR defect?
- 1. immature CFTR synthesized
- 2. most common mutation - ΔF508
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What occurs in a Class III CFTR defect?
- 1. CFTR synthesized and placed in membrane
- 2. secondary messenger activation and regulation dysfunctional
- 3. most common mutation - G551D
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What occurs in a Class IV CFTR defect?
- 1. CFTR synthesized and placed in membrane2. chloride ion flow reduced
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What occurs in a Class V CFTR defect?
CFTR synthesis and processing is partially defective
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What occurs in a Class VI CFTR defect?
- 1. CFTR synthesized and place in membrane
- 2. other ion flow reduced
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What evidence of CFTR dysfunction is required for CF diagnosis?
- 1. Two or more mutations in CFTR
- 2. Two or more sweat chloride tests over 60 mmol/L
- 3. Abnormal nasal potential difference
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How is prenatal testing done for CF diagnosis?
- 1. parents carry CF trait
- 2. echogenic bowel detected on fetal ultrasound
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In which states are newborns screened for CF and which mutations are screened?
- Screened in all 50 states
- Screened for the 23 most common mutations
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What is the sweat chloride test for CF diagnosis?
pilocarpine induced sweating
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What defines an abnormal result in the sweat chloride test (mmol/L)?
Abnormal = >60 mmol/L
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What defines an intermediate result of the sweat chloride test (mmol/L)?
- < 6 months of age: 30-59 mmol/L
- > 6 months of age: 40-59 mmol/L
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What is a normal value of the sweat chloride test for CF diagnosis?
- < 6 months of age: < 30 mmol/L
- > 6 months of age: < 40 mmol/L
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What is the next step of CF diagnosis after a sweat choride test returns with intermediate results?
DNA testing
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What does > 2 CFTR mutations indicate?
confirmed CF diagnosis
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What does < 1 CFTR mutation indicate in the sweat test?
Questionable CF
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What must occur if a questionable CF diagnosis occurs?
- 1. repeat sweat test or
- 2. expand DNA testing
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What occurs if a repeat sweat test is > 60 mmol/L?
What occurs if a repeat sweat test is < 60 mmol/L?
- > 60 mmol/L: confirmed CF
- < 60 mmol/L: follow clinically
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What occurs if an expanded DNA test reveals > 2 CFTR or < 1 CFTR mutation?
- > 2 CFTR mutations: confirmed CF
- < 1 CFTR mutation: follow clinically
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What is the gastrointestinal presentation of CF?
- 1. meconium ileus
- 2. failure to thrive
- 3. steatorrhea
- 4. edema
- 5. hypoproteinemia
- 6. anemia
- 7. electrolyte variability
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What are the pancreatic manifestations of CF?
- 1. pancreatic insufficiency
- 2. CF-related diabetes
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How many patients will experience pancreatic insufficiency?
85%
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What happens to pancreatic function with age?
Pancreated functions decrease with age
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Which classes of CF are correlated with genotype?
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When does duct obstruction begin as a pancreatic insufficiency in CF?
May begin in 2nd trimester
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What level of the fecal elastase testing indicates insufficiency?
Less than 200 mcg/gram
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What are the general principles associated with pancreatic enzyme replacement therapy (PERT)?
- 1. enzymes: lipase, protease, amylase
- 2. dosed based on lipase units per weight or fat intake
- 3. coating dissolves in alkaline environments
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What is the weight-based dosing of PERT?
- < 4yo: 1000 units of lipase per kg per meal
- > 4yo: 500 units of lipase per kg per meal
- maximum of 2500 units of lipase per kg per meal
- doses given with fatty snacks
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What is the fat-based dosing for PERT?
- 1. 2000 units of lipase per 120mL of feedings
- 2. maximum of 2500 units of lipase per kg per feeding
- 3. maximum daily dose of 10,000 unis of lipase per kig
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What vitamin replacement is necessary for PERT?
- Start with diagnosis
- Fat-soluble vitamin replacement:
- Vitamin A
- Vitamin D
- Vitamin E
- Vitamin K
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What are the risk factors for CF-related diabetes?
- advanced age
- female
- pancreatic insufficiency ΔF508 mutation
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What are the intestinal manifestations of CF?
- 1. GERD
- 2. Meconium ileus
- 3. Distal intestinal obstruction syndrome (DIOS)
- 4. Constipation
- 5. Intussusception
- 6. Small bowel bacterial overgrowth
- 7. Rectal prolapse
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Discuss the pertinant information associated with GERD and CF.
- 6-8 times more prevalent in CF patients
- Reflux episodes higher than control populations
- Esophageal acid exposure higher than controls
- -decreased LES tone
- -increased intra-abdominal pressure
- -hyperinflated lungs
- -chest physiotherapy
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What are the available treatments for GERD associated with CF?
- 1. Chest physiotherapy
- 2. Proton Pump Inhibitors
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When should chest physiotherapy for GERD be administered?
perform prior to meals
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What is the dosing of PPI's for the treatment of GERD?
- 0.2 - 2 mg/kg/day
- 1-2 times daily
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How often does meconium ileus occur in CF patients?
10% of CF presentations
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What are the 2 types of classification of meconium ileus?
- 1. simple
- 2. complex (40%)
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What are some common problems associated with complex meconium ileus?
- 1. perforation
- 2. atresia
- 3. meconium peritonitis
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How is meconium ileus diagnosed?
confirmed with contrast enema
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What is DIOS?
- 1. common if patient has histor of meconium ileus
- 2. no relationships with mutations
- 3. acute blockage of the ileum
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How are complete acute blockages of the ileum (DIOS) cleared?
1. Surgery (complete)
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How are partial acute blockages of the ileum (DIOS) cleared?
- 1. Rehydration
- 2. Osmotic laxatives (polyethylene glycol, gastrografin, electrolye solution)
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What are the GI classifications of CF?
- 1. pancreatic manifestations
- 2. intestinal manifestations
- 3. hepatobiliary
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What hepatobiliary complications are associated with CF?
- 1. biliary cirrhosis
- 2. liver disease
- 3. neonatal cholestasis
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What disease does biliary cirrhosis lead to and how is it treated?
- Leads to liver disease
- Treatment: Ursodiol 30 mg/kg/day divided twice daily
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How is liver disease recognized?
slight elevations in alkaline phosphatase
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How is neonatal cholestasis recognized?
- 1. history of meconium ileus
- 2. prolonged parenteral nutrition
- 3. increased risk of liver ccirrhosis
- 4. treatment: ursodiol 30 mg/kg/day divided 2-3 times daily
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What are the pulmonary presentations of CF?
- 1. recurrent cough
- 2. persistent cough
- 3. prolonged wheezing
- 4. recurrent bronchiolitis
- 5. produtive cough
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Discuss reactive airway disease.
- 1. Directly related to lunch disease severity
- 2. Treatment: bronchodilators
- 3. worsening lunch disease: reduction in smooth muscle support system; collapsing muscle worsens obstruction
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Discuss Chronic pulmonary issues associated with CF.
- 1. Chronic airway obstruction
- 2. Bacterial colonization of clogged airways
- 3. Chronic medictions
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