Which genetic disorder causes thick mucus in the lungs leading to recurrent infections?

• A. COPD
• B. Emphysema
• C. Pleurisy
• D. Cystic fibrosis

Answer: (D)

Cystic fibrosis is a genetic disorder that causes thick, sticky mucus in the airways, which leads to recurrent lung infections. The problem comes from mutations in the CFTR gene that disrupt chloride transport across epithelial cells, dehydrating the airway surface liquid. This thick mucus blocks airways and creates a favorable environment for bacteria, such as Pseudomonas, resulting in frequent infections and chronic cough. This pattern distinguishes it from COPD or emphysema, which are usually related to smoking and involve airflow limitation rather than a primary mucus production defect, and from pleurisy, which is inflammation of the lung lining rather than a mucus-related disease.