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Cystic Fibrosis. Board Review February 11, 2008. Cystic Fibrosis. Mutation in CFTR gene--epithelial chloride channels mutation causes decreased Cl transport and Na hyperabsorption leading to thick secretions most common mutation is delta-F508 (70%), however, over 1500 mutations exist
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Cystic Fibrosis Board Review February 11, 2008
Cystic Fibrosis • Mutation in CFTR gene--epithelial chloride channels • mutation causes decreased Cl transport and Na hyperabsorption leading to thick secretions • most common mutation is delta-F508 (70%), however, over 1500 mutations exist • Autosomal recessive inheritance • 1 in 25 to 30 Caucasians is a carrier, making disease prevalence 1 in 3300
The lungs • Major cause of death (usually by 30 years) is progressive respiratory disease. • Increased secretions lead to obstruction, leading to repeated infections (especially psuedomonas), bronchiectasis, and decline in lung function, causing respiratory failure often with a component of pulmonary hypertension and cor pulmonale
The pancreas • Pancreatic ducts are obstructed by thick secretions, leading to decreased excretion of enzymes into the intestine. • Pancreas is autodigested and replaced by scar tissue, resulting in decreased breakdown of fat and protein • Fat and protein malabsorption, fat-soluble vitamin deficiency
A (retinol) blindness D rickets K prolonged prothrombin time 2, 7, 9, 10--vitamin K dependant factors E (tocopherol) ptosis proprioception truncal ataxia Fat soluble vitamins
General FTT GI meconium ileus in neonate foul smelling stools, bloating rectal prolapse impaction/obstruction pancreatitis low albumin, low sodium cholelithiasis, cholecystitis cirrhosis, portal hypertension neonatal hyperbilirubinemia fat soluble vitamin deficiency Respiratory clubbing asthma COPD, barrel chest productive cough, hemoptysis nasal polyps pneumothorax/mediastinum cor pulmonale, RVH Metabolic dehydration (low Na, low Cl) metabolic alkalosis (esp neonate) DM heat stroke GU infertility in males Presentation
Diagnosis • Elevated serum trypsinogen in neonate • Gene testing • 87 mutation panel (92% sensitivity) • 1300 mutation panel (97 - 99% sensitivity) • GOLD STANDARD: CHLORIDE SWEAT TEST • <40 mEq/L--negative • 40 - 60 mEq/L--equivocal, needs repeat • >60 mEq/L--positive, needs confirmation
False positives adrenal insufficiency nephrogenic DI hypothyroidism mucopolysaccharidosis G6P deficiency hypoproteinemia anemia from poor nutrition False negatives severe malnutrition with edema too little sweat inexperienced tester Diagnosis
Treatment • For acute respiratory infections: hospitalization with PCN and aminoglycoside, pulmonary toilet • baseline pulmonary therapy • aerosols (bronchodilation) • chest physical therapy • aerosolized antibiotics • systemic steroids or expectorants--not indicated
Treatment • Nutritional therapy • high fat, high protein diet • pancreatic enzyme replacements • vitamin and mineral supplements • Other • no support for growth hormone • pulmonary transplant--must transplant both lungs simultaneously!
Prognosis • Life expectancy of about 32 years at best • Poorer prognosis in: • females • low SES • severe neonatal pulmonary disease