Cystic Fibrosis in Children

A child with recurrent pneumonia, greasy stools, and a salty taste when kissed — three different organ systems pointing to one defective chloride channel.

Cystic fibrosis is an autosomal recessive disorder caused by a defective CFTR protein on chromosome 7, producing abnormally thick, sticky mucus that obstructs the lungs, pancreas, and reproductive tract. The sweat chloride test is the gold standard for diagnosis: a level above 60 mEq/L is diagnostic; 30–59 mEq/L is borderline. Pulmonary involvement drives morbidity — thick secretions trap bacteria (especially Pseudomonas aeruginosa and Staphylococcus aureus), causing chronic infections and progressive lung damage. Pancreatic insufficiency occurs in roughly 85% of children, blocking digestive enzyme release and causing malabsorption, steatorrhea (bulky, foul-smelling, greasy stools), and failure to thrive. These children require pancreatic enzyme replacement (pancrelipase) given with every meal and snack — not before, not after, but with food. A high-calorie, high-protein, high-fat diet with fat-soluble vitamin supplements (A, D, E, K) is standard because malabsorption creates chronic deficits. Airway clearance techniques — chest physiotherapy, flutter valves, high-frequency chest wall oscillation — are performed multiple times daily, ideally before meals to avoid vomiting. Dornase alfa (Pulmozyme) thins mucus by breaking down DNA from dead neutrophils in the airways.

Key Distinctions

Don't confuse CF steatorrhea with lactose intolerance — CF stools are greasy and foul from fat malabsorption, not watery and acidic. Students mix up the sweat test direction: CF children have elevated sweat chloride (salty skin), not decreased. Pancreatic enzymes are given WITH food, not on an empty stomach — timing errors render them ineffective.

Clinical Pearl

Think "salty kid who can't breathe or digest": sweat chloride confirms it, chest PT clears it, pancrelipase with every meal absorbs it, and fat-soluble vitamins (ADEK) replace what's lost.