Cystic Fibrosis
A 5-year-old boy of consanguineous parents has had four admissions for pneumonia, chronic bulky greasy foul-smelling stools since infancy, and weight below the 3rd percentile despite a good appetite. He has bilateral nasal polyps, digital clubbing, and coarse crackles at both lung bases. Sweat chloride is 92 mmol/L on two occasions and sputum culture grows Pseudomonas aeruginosa. Which is the most common long-term pulmonary complication of his underlying disease?
- A.Emphysema
- B.Bronchogenic carcinoma
- C.BronchiectasisCorrect
- D.Allergic rhinitis
Explanation
This child has cystic fibrosis, confirmed by a sweat chloride above 60 mmol/L with recurrent pneumonia, steatorrhea, failure to thrive, and bilateral nasal polyps, and the most common long-term pulmonary complication is bronchiectasis. Defective CFTR chloride transport produces dehydrated, viscous airway secretions with impaired mucociliary clearance, leading to chronic endobronchial infection with Staphylococcus aureus and later Pseudomonas aeruginosa. The resulting neutrophilic inflammation releases elastase and other proteases that destroy the bronchial wall, causing irreversible airway dilatation, which is bronchiectasis, and this underlies the chronic productive cough, clubbing, and progressive obstructive lung disease. Other important pulmonary complications include hemoptysis, pneumothorax, empyema, and allergic bronchopulmonary aspergillosis, while extrapulmonary problems include pancreatic insufficiency, cystic fibrosis related diabetes, distal intestinal obstruction syndrome, and male infertility. Emphysema is a disease of alveolar wall destruction typical of smoking and alpha-1 antitrypsin deficiency, not the airway-centred damage of cystic fibrosis. Bronchogenic carcinoma is not a recognized common complication in this population. Allergic rhinitis is common in the general population and may coexist with nasal polyps but is not a pulmonary complication and does not drive morbidity. Management centres on airway clearance, inhaled mucolytics such as dornase alfa and hypertonic saline, aggressive antibiotic therapy, pancreatic enzyme replacement, fat-soluble vitamin supplementation, and CFTR modulator therapy when the genotype is eligible.
Why each option
- A.
- Emphysema reflects alveolar destruction from smoking or alpha-1 antitrypsin deficiency, not the airway-centred injury of cystic fibrosis.
- B.
- Lung cancer is not a recognized common complication of cystic fibrosis in children or young adults.
- C.
- Correct. Chronic infection and neutrophilic inflammation destroy bronchial walls, making bronchiectasis the hallmark pulmonary complication.
- D.
- Allergic rhinitis is an upper airway allergic condition and is not the major pulmonary complication driving morbidity.
Reference: Nelson Textbook of Pediatrics, 22nd ed., 2024, Cystic Fibrosis
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