Cystic Fibrosis

Cystic fibrosis isn't just a pediatric disease — adults with CF now outnumber children, and the thick, tenacious secretions affect far more than the lungs.

Cystic fibrosis is an autosomal recessive genetic disorder caused by a defective CFTR protein that regulates chloride and bicarbonate transport across epithelial cells. The result: abnormally thick, sticky mucus in the lungs, pancreas, liver, and reproductive tract. In the lungs, this mucus obstructs airways, traps bacteria (especially Pseudomonas aeruginosa and Staphylococcus aureus), and triggers a cycle of chronic infection and inflammation that progressively destroys lung tissue. Sweat chloride testing confirms diagnosis — a value greater than 60 mEq/L is diagnostic. Pancreatic insufficiency affects roughly 85% of patients, causing malabsorption of fats and fat-soluble vitamins (A, D, E, K). Stools are large, greasy, and foul-smelling (steatorrhea). Nursing priorities center on aggressive airway clearance (chest physiotherapy, high-frequency chest wall oscillation, flutter valves), administering pancreatic enzyme replacements (pancrelipase) with every meal and snack, maintaining a high-calorie, high-protein, high-fat diet — the opposite of typical dietary teaching — and monitoring for respiratory infections. Dornase alfa (Pulmozyme) thins mucus by breaking down extracellular DNA in sputum. CFTR modulator therapy (e.g., elexacaftor/tezacaftor/ivacaftor) targets the underlying protein defect and has dramatically improved outcomes.

Key Distinctions

Don't confuse CF's high-fat, high-calorie diet with the low-fat diets taught for pancreatitis or gallbladder disease — CF patients need more fat because they can't absorb it efficiently. Students mix up sweat chloride testing (diagnostic for CF) with sputum chloride. Pancreatic enzymes must be given with food, not on an empty stomach — timing is the testable detail.

Clinical Pearl

Salty skin, fat stools, Pseudomonas cough — if the sweat tastes like a pretzel and the stool floats, think CF.